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Showing 23 results for Scaffold
Volume 5, Issue 2 (9-2021)
Abstract
The rise of bacterial infections has become a serious problem in human societies. As a result, the development of nanocomposite materials based on biocompatible and non-hazardous materials, besides having antimicrobial and biocompatibility or non-cytotoxicity, associated with unique structural properties, possesses a great importance. Research approach: In this study, bacterial cellulose (BC)/polypyrrole (PPy) and zinc nanoparticles (ZnO), which simultaneously have antimicrobial properties and cell proliferation, were introduced as a new generation of nanocomposite scaffolds produced by freeze-drying. To begin with, ZnO with different weight percentages of 1%, 3% and 5% was added to BC and then PPy in the amount of 2 mmol was embedded in the structure by in situ polymerization. FESEM images proved that the nanofibrous and porous structure of BC was also preserved in the presence of PPy and ZnO. However, after adding PPy and ZnO, they formed a dense structure and microstructure of grape clusters. By adding 2 mmol PPy into BC and upon in situ synthesizing, the tensile strength and Young modulus of BC were significantly reduced to 71 MPa and 2.5 GPa, respectively. On the other hand, with the addition of ZnO nanoparticles, the mechanical properties significantly increased (both of Young modulus and tensile strength compared to BC/PPy samples) due to the compaction of the nanocomposite aerogel’s structure and the formation of the interface of ZnO nanoparticles with both polymers of BC and PPy. The observation of the inhibition zone in the culture medium containing two gram-positive and negative bacteria, well proved the antibacterial ability of ternary nanocomposite scaffolds. The results of MT9 related to L929 on aerogels showed that by adding 3% of ZnO nanoparticles, adhesion and cell proliferation increased significantly during different days of 1 day, 5 days and 7 days of culture.
Volume 8, Issue 1 (3-2024)
Abstract
Research subject: This study aims to improve the biocompatibility, bioactivity, and mechanical properties of gelatin-based composite scaffolds by coating them with polyethylene glycol (PEG) doped with bioactive glasses (BGs) containing zinc and magnesium.
Research approach: A response surface methodology (RSM) was used to model and evaluate the effects of two independent variables: the PEG/Gel weight ratio (X1) and the BG weight percentage (X2). The responses investigated included ultimate strength, Young's modulus, elongation at break, swelling percentage, erosion percentage, and moisture absorption percentage.
Main results: Optimal conditions were determined to obtain scaffolds with suitable mechanical strength, biocompatibility and degradability. Analysis of variance (ANOVA) was used to obtain the best model describing the influence of each independent variable on the responses. The optimal scaffold formulation was selected based on software-defined parameters. The FTIR spectrum was used to analyze the functional groups present on the surface of the samples. The FTIR spectrum of the synthesized BGs showed a broad vibrational band in the range of 900 to 1100 cm-1, which is attributed to the asymmetric Si-O-Si stretching band. The FTIR spectrum of the PEG/Gel/BG composite confirmed the presence of BG in the scaffolds and the interaction between the polymer matrix and BG. Increasing the amount of BG relative to the polymer scaffold led to a decrease in pore size and consequently, a decrease in the scaffold's swelling percentage. The effect of varying the BG weight percentage on tensile strength was greater than that of the PEG/Gel weight ratio. The tensile strength increased significantly due to the good interaction between the polymer scaffold and BG, as well as the uniform dispersion of BG within the polymer matrix. SEM images indicated that cells penetrated well into the scaffolds and formed a suitable three-dimensional cellular network. Cytotoxicity, cell attachment and proliferation, and osteogenic differentiation were evaluated using the MTT test and by culturing MG-63 cells on the scaffold. Cell viability showed no significant difference between the tested and control samples.
T.p. Abedi Mohtasab, E. Tamjid, R. Haji-Hosseini,
Volume 10, Issue 3 (9-2019)
Volume 10, Issue 3 (9-2019)
Abstract
Aims: Recently, polymer-based nanofibrous scaffolds have attracted great attention due to their significant antibacterial properties in the field of dermatological applications. In this study, a polycaprolactone-based nanofibrous scaffold has been fabricated using the electrospinning method. The aim of this study was to evaluate the antibacterial effect of electrospun nanofibrous structures. Materials and Methods: In this experimental study, the structure and bacterial attachment on polymeric nanofibrous scaffolds were studied by Scanning Electron Microscopy (SEM). In addition, antibacterial properties of nanofibrous scaffolds were studied on two gram-negative bacteria of Escherichia coli and Pseudomonas aeruginosa and two gram-positive bacteria of Staphylococcus aureus and Streptococcus mutans, using microdilution method and biofilm assay. Moreover, MTT assay was performed on HeLa and human fibrosarcoma cell line (HT1080) cancerous cell lines to evaluate the cell viability.
Findings: The results of this study showed that nanofibrous scaffold revealed a significant antimicrobial and anti-biofilm formation effect on all of the studied bacterial strains, but in microscopic observations and microdilution assay was observed on Pseudomonas aeruginosa in 1mg/ml of nanofibrous scaffold extract concentration, while the major effect in biofilm assay was observed in 8µg/ml of extract concentration. Moreover, the cell viability studies showed that the most significant effect was shown on HT1080 cell line which has drastically decreased by 40% after 48 hours in comparison with the control.
Conclusion: These results show that electrospun nanofibrous PCL-based scaffolds are potentially promising for dermal tissue engineering applications, due to anti-biofilm effects and capability of reducing the number of cancerous cells in the wound site.
A. Bakhshian Nik, B. Vahidi,
Volume 10, Issue 4 (12-2019)
Volume 10, Issue 4 (12-2019)
Abstract
Aims: In bone tissue engineering, the scaffold as a supportive structure, plays a vital role. Putting the scaffold in dynamic cell culture, such as perfusion bioreactor, makes the role of mechanical parameters such as shear stress and hydrodynamic pressure more important. On the other hand, these mechanical parameters are influenced by scaffold architecture. In this study, the effects of bone scaffold architecture on mechanical stimuli have been analyzed and their effects on the mesenchymal stem cell fate have been predicted.
Material & Methods: Using the tools of computer simulation, five bone scaffolds (Gyroid, high porous Gyroid, Diamond, IWP, and gradient architecture Gyroid) based on mathematical functions of minimal surfaces were designed and exposed in a simulated dynamic cell culture under the inlet velocities of 1, 10, 25, 50, and 100μm/s. Cell accumulation on the inner part of the scaffold was considered as an 8.5-micron layer. This layer was designed for Gyroid and IWP scaffolds.
Findings: Based on the results, Diamond scaffold showed the most efficient performance from the homogeneity of stresses point of view. In the presence of the cell layer, the von Mises stress was reported as 60 and 50 mPa on the Gyroid and IWP scaffolds, respectively which eases osteogenic differentiation.
Conclusion: In gradient architecture scaffolds under dynamic conditions, there is a gradient in shear stress that causes various signaling in different positions of theses scaffold and facilitates multi-differentiation of the cells on the same scaffold.
Mahsa Bohlouli, Elnaz Tamjid, Soheila Mohammadi, Maryam Nikkhah,
Volume 11, Issue 1 (3-2020)
Volume 11, Issue 1 (3-2020)
Abstract
Since one of the main problems in bone tissue repair is the bacterial infections, recently the development of drug-eluting nanocomposite scaffolds for bone regenerative medicine applications has attracted significant attention. In this study Polycaprolactone (PCL)-based composite scaffolds containing 10vol% of titanium dioxide nanoparticles (~21nm), and bioactive glass particles (~6µm), were prepared without drug and also loaded by Tetracycline hydrochloride (TCH) antibiotic (0.57, 1.15 mg/mL) through solvent casting method for bone tissue engineering applications. Structural characterizations based on Scanning Electron Microscopy (SEM), and FTIR analysis were utilized to study the chemical bonds of glass/ceramic particles, and antibiotic crystals on the surface. In addition, in vitro cytotoxicity, and antibacterial analysis were performed by MTT, and Agar well-diffusion assays, respectively. In this study polymeric and composite scaffolds were fabricated with TCH clusters decorated on the surface. It was shown that the bioactive glass/PCL scaffolds loaded by 0.57 mg/mL of TCH revealed significant antibacterial effect, despite the acceptable cell viability. These scaffolds seem to be of interest as a potential candidate in drug-eluting scaffolds for bone tissue engineering applications.
Volume 12, Issue 1 (3-2021)
Abstract
Despite growing interest in the studies on ZPD, its operation in the forms of individualized and group-wide has been controversial. To cast some empirical light on the issue, this study was designed to quantitatively and comparatively study the applicability of the two scenarios of ZPD-based instructions to the writing accuracy of Iranian EFL learners in terms of learners' types (low vs. high scorers). To this end, 118 EFL learners identified as homogeneous based on TOEFL ITP test were randomly assigned into two equal experimental groups (individualized and group-wide ZPD-based) which respectively received compatible instructions utilizing individual and whole-class scaffolding techniques. The treatments were allocated to the groups in a random manner within homogeneous blocks. Prior to and after the treatments, three tests (two writing tests and one ZPD test) were administered to measure both groups’ writing accuracy and their ZPD levels. A ZPD test was also administered in the mid of treatments. Results revealed that I-ZPD-based instruction is constructive to the low scorers, and GW-ZPD-based instruction is not constructive to both low and high scorers. The findings pointed to the use of ZPD-based instructions in TEFL writing in meaningful contexts and thereby showing impacts made on the writing accuracy of learners. The study, indeed, yield support to the feasibility of GW-ZPD measurement along with I-ZPD approach.
1. Introduction
Vygotsky’s (1978) Socio-Cultural Theory (SCT) is regarded as a major breakthrough in the field of social psychology and as a resultant in education in general and language education in particular given the significant role of sign system in social construction. SCT is based on certain macro principles mainly including developmental analysis of mental program, social basis of human cognition, scaffolding, mediated learning, and ZPD. In Vygotsky’s sense, scaffolding is defined as the “role of teachers and others in supporting the learner’s development and providing support structures to get to that next stage or level” (Raymond, 2000, p.176, as cited in Van Der Stuyf, 2002).
While SCT principles have been implemented as to certain skills of language ability, writing skill seems to have been left intact to some extent. While writing is one of the main and productive skills, as well as a significant requirement for EFL learners. It is the most difficult skill to master because of its difficulties in generating, organizing, and translating ideas into a readable text (Richards & Renandya, 2002). At the same time, writing is often considered as the most difficult skill to be mastered (Hapsari, 2011). Researchers (Ellis, 2003; Skehan 1998) are now in agreement that L2 proficiency, in general, and writing proficiency, in particular, are multi-componential in nature, and that their principal dimensions can be adequately and comprehensively captured by the notions of complexity, accuracy and fluency (CAF; Housen and Kuiken, 2009).
Writing accuracy refers to “the extent to which the language produced conforms to the target language norms” (Skehan & Foster, 1996, p. 232). Accuracy refers to the production of error-free language. It is estimated by considering the percentage of error‐free clauses (Skehan & Foster, 1996; Skehan & Foster, 1999; Yuan & Ellis, 2004) and the percentage of correct use of target features (Crookes, 1989, as cited in Ellis, 2004).
Scaffolding associates peer-and cooperative endeavor but its implementation seems unimaginable in the absence of ZPD measurement and operationalization. Analogous to society, classroom setting is the combination individuals working and cooperating in a community. It is a must and, of course, to some extent more feasible to identify and probably measure one’s ZPD in a bid to offer some kind of compatible education and input. Nevertheless, pure individualization may look at odd with the other principles of SCT, which is strongly in favor of socially-mediated learning and defining learning as movement along the continuum of intra-personal and inter-personal processes. Such a social, cooperative, and collaborative nature of learning and development requires an initiative to measure both I-ZPD along with GW-ZPD such that the expected mediation, scaffolding and inter-personal and intra-personal processes can be compatible and cooperative. Then, the main problem to be addressed is twofold: operationalization of the varieties of ZPD-based instruction (i.e. I-ZPD vs. GW-ZPD), and incorporation of these two varieties in teaching writing skills in relation to the learners’ variables such as their proficiency level in the form of e,g, test scores.
Based on the significance of the two categories of ZDP and writing in EFL contexts on one hand and the undesirable status of the writing performance of Iranian EFL learners (Hasani and Moghadam, 2012) on the other, this very study is rationalized on the following two premises:
- the interfaces between EFL learners’ writing quality in terms of accuracy and the two types of ZPD-based instructions (i.e. individualized and group-wide)
- these instructions’ effect on enhancing writing quality (i.e. accuracy) of Iranian EFL learners in terms of learners' types (i.e. low and high scorers).
In order to accomplish these objectives, the present study, focusing first and foremost on measuring each target learner’s I-ZPD and then on their GW-ZPD or average ZPD, and second on the feasibility and application of each ZPD scenarios in developing writing ability of Iranian EFL learners. More specifically, the following main question realized through four minor ones were posed:
1. Is there any significant difference in the effect of group-wide ZPD-based instruction and individualized ZPD-based instruction on the writing accuracy of Iranian EFL learners in terms of learners' types (low vs. high scorers)?
1.1 Does GW-ZPD-based instruction and I-ZPD-based instruction have different impact on the accuracy of EFL low-scored learners’ writing?
1.2 Minor Q: Does GW-ZPD-based instruction and I-ZPD-based instruction have different impact on the accuracy of EFL high-scored learners’ writing?
1.3 Minor Q: Does GW-ZPD-based instruction have significantly different effect on low scorers compared to high scorers in developing their writing accuracy?
1.4 Minor Q: Does I-ZPD-based instruction have significantly different effect on low scorers compared to high scorers in developing their writing accuracy?
2. Methodology
The research was conducted empirically through the implementation of the pretest-treatment-posttest design. A homogeneous group of 118 undergraduate, intermediate Persian EFL learners of both genders in the age range of 18 to 22 years old majored in Translation Studies from a university in Tehran students was selected based on their performance on their TOEFL ITP. Then, three pre- and post-tests (two writing tests and a ZPD test) were administered in the first and the last sessions, respectively. The two treatment groups were formed randomly to receive two types of ZPD-based instructions (individualized and group-wide). Another ZPD-test was also administered in the sixth session of the treatment in order to study ZPD development of the two treatment groups and give them their most suitable ZPD-based instructions.
Ultimately, comparison was made between the pre- and post-tests’ scores of the two intact writing classes. The learners’ ZPD development was measured before, after and in the mid of treatment using Raven’s Standard Progressive Matrices (SPM; Raven, 1998). Their ZPD development was, indeed, assessed and analyzed on a weekly basis and a monthly basis (three times in the semester -- before, after, and in the mid of treatment) taking the advantage of Kozulin and Garb’s (2002) learning potential score’s (LPS) formula.
To estimate the inter-rater reliability between the two raters, a randomly selected cluster of writing papers, including 28 sets of papers, scored by the two raters. Running Pearson correlations between these score sets indicated that there were significant agreements between the scores of writing accuracy (r (27) = .73, P < .05 representing a large effect size) as provided by the two raters. As a result, the researcher employed the mean of the two scores provided by the two raters as the final score for each participant’s writing performance in terms of their writing complexity, accuracy.
The treatment was applied for two consequent semesters in order to increase the intra-rater reliability of the findings. Running Pearson correlations between the score sets taken from the first and second semester’s participants of the study indicated that there were significant agreements between the two sets of scores of the participants’ writing performance (r (32) = .83, P < .05 representing a large effect size). As a result, the researcher employed the mean of the two sets of scores taken from the participants during the first and the second semesters as the final score for each participant’s writing performance in terms of their writing accuracy.
3. Results and Discussion
Due to the non-interval nature of the data, all research questions were probed through non-parametric analysis of covariance (ANCOVA) and Friedman’s test.
As to the first and the second minor research questions about the impact of the two types of ZPD-based instructions on the writing accuracy of the low scorers, and the high-scorers, the researchers taking advantage of the criteria proposed by Wigglesworth and Storch (2009) for the measurement of writing accuracy, came up with the following findings:
- The I-ZPD-based instruction helped the low-scored learners outperform GW-ZPD-based instruction group on the accuracy of writing (+.003 vs. -.136).
- While the I-ZPD-based instruction acted as a stronger deterrent against writing accuracy of the high-scored learners than the GW-ZPD-based instruction (-.037 vs. -.078).
As to the third and the fourth minor research questions on the effect of the GW-ZPD-based instruction, and the effect of the I-ZPD-based instruction on the writing accuracy of the low scorers compared to high scorers, the respective ANCOVA came up with the following findings:
- The GW-ZPD-based instruction act as a deterrent against writing accuracy of the low scorers (-.136) and high scorers (-.037) respectively significantly and slightly.
- And, the I-ZPD-based instruction acted slightly as a deterrent against writing accuracy of the high scorers (-.078) while acting as a very slight developer of writing accuracy of the low scorers (+.003).
As to the main question on the significant difference in the effect of the g-wide ZPD-based instruction and the I-ZPD-based instruction on the writing accuracy of Iranian EFL learners in terms of the learners' levels (i.e., low vs. high scorers), the researcher defined the I-ZPD-based instruction’s positive impacts on the writing accuracy of the low scorers, and the g-wide ZPD-based instruction’s negative impacts on the writing accuracy of the both levels of the learners (more on the low scorers than the high scorers).
4. Conclusion and Implications
In brief, two main conclusions from the above-mentioned discussion were drawn: 1) I-ZPD-based instruction is constructive to the writing accuracy of the low-scored learners. 2) GW-ZPD-based instruction is more destructive to the writing accuracy of the low scorers than the high scorers.
The results of the present study cast new light on the nature of ZPD, highlighting the significant difference between the two ways of its running (i.e. individualized vs. group-wide) and the achievements of the two types of EFL learners (i.e. low scorers vs. high scorers). These findings were in line with the results of the studies conducted by many other researchers on the individualized scaffolding technique of conference writing (e.g. Aljaafreh & Lantolf, 1994; De Guerrero & Villamil, 1996; Nassaji & Swain, 2010) and on the whole-class scaffolding technique of template studied by several other scholars (e.g. Baleghizadeh et al., 2011; and Smit et al.,2013).
This study has significant pedagogical implications. Syllabus designers can apply two types of scaffoldings (used in the two types of ZPD-based instructions; i.e. group-wide and individualized) effective for the writing accuracy of the relevant low- and high-scored EFL learners to textbooks. The merit of these two types of ZPD-based instructions is that they challenge writing accuracy of the two types of EFL learners differently but in their ZPD providing guided free exploration.
Volume 13, Issue 3 (8-2010)
Abstract
Objective: Allogeneic transplantation with umbilical cord blood (UCB) in adult recipients is limited mainly by a low CD34+ cell dose. To overcome this shortcoming, human placenta as a novel source of human mesenchymal progenitor cell (MPC)- unrestricted somatic stem cells (USSC)- was incorporated in an attempt to expand CD34+ cells from UCB. To provide a similar environment in vitro, we coated DBM scaffold with USSC cells as the matrix for support UCB-CD34+ cells growth. Materials and Methods: Human placenta USSC was isolated and characterized by morphologic and immunophenotypical analysis. UCB CD34+ cells were expanded by coculture with placental USSC in 2D and 3D environment. Suitable aliquots of cells were used to monitor cell production, clonogenic activity, and long-term culture-initiating culture (LTC-IC) output. Results: Ex vivo expansion of UCB hematopoietic cells, when cultured in different 2D conditions and 3D condition for 3 weeks, was significantly enhanced, the total cell count increased within the 28-day period. For total CFC, the highest CFC expansion was observed at day 14. Flow cytometry analysis of the percentage of CD34+ cells showed a decline in USSC cocultures in 2D and 3D condition at 3 weeks. Conclusion: These results strongly suggest that human USSC may be a suitable feeder layer for expansion of hematopoietic progenitors from UCB in vitro and USSC- coated DBM can therefore provide an ex vivo mimicry of bone marrow by enhancing of surface/ volume ratio and feeder layers,recapitulate the desired niche, and provide a suitable environment for stem cell expansion and differentiation.
Volume 13, Issue 3 (8-2022)
Abstract
Scaffolding research has been widely investigated involving parent-child within the first language (L1) context without considering the cognitive issues and Intelligence Quotients (IQ) aspects as crucial precursors of the scaffolding process. This case study aims to find emergent themes and theorize potential scaffolding theory from the interaction of two-second language (L2) Autism Spectrum Disorder (ASD) children and normal parents with minimum English exposure, cognitive disorders, and different IQ levels on the mobile story-sharing application. Participant observations and in-depth interviews on scaffolding using story-sharing activities among children, parents, and researchers were conducted every week for six months. Thematic analysis was implemented inductively and interpreted by two experts to find the emerging variation of scaffolding theories. The results showed that ASD learners' scaffolding process involved more complex stages than the previous studies. The complexities of scaffolding involved repetitive recall, translating, imitating, cooperating, target and crises. ASD learners could write a simple phrase and short sentence after exhaustive efforts. Since ASD learners’ previous vocabulary mastery was excluded, it is worth pursuing further researchers to examine learners’ vocabulary and story writing development using the same application.
Shokoufeh Mehrtashfar, Mahboubeh Kabiri,
Volume 13, Issue 3 (1-2023)
Volume 13, Issue 3 (1-2023)
Abstract
Occurrence of various types of incidents such as road accidents, damage and injuries during sports activities as well as some diseases can lead to the destruction and resorption of osteochondral tissue and cause many problems in health and quality of life of the patient, therefore control and repairing these defects is one of the major challenges in the field of regenerative medicine. Since osteochondral defects involve damage to both articular cartilage and underlying subchondral bone, the demands of bone, cartilage, and bone cartilage interface should be taken into account for repair. Current clinical therapies are more palliative and less therapeutic. Hence, due to the limitations of existing treatment methods over the past decade, the use of tissue engineering as an effective and low-risk treatment method for the treatment of many diseases, especially bone-cartilage lesions has been introduced. In this approach, some of the limitations of previous methods could be overcome by transplanting osteochondral composite tissues, which have been obtained by combining patient's own cells with three-dimensional porous biomaterials of predetermined shape and size. So far, various strategies for scaffold fabrication have been used to repair osteochondral defects, including single-phase, multilayer, and graded structures. In this study, some common strategies in tissue engineering as well as the challenges ahead are briefly discussed.
Lida Shahghasempour, Simzar Hosseinzadeh, Azam Haddadi, Mahboubeh Kabiri,
Volume 13, Issue 4 (1-2023)
Volume 13, Issue 4 (1-2023)
Abstract
Wound healing and skin remodeling occur directly after skin damage, so the use of platelet rich growth factors (PRGF) and probiotics is important to accelerate this process because of their positive effects on wound healing and antibacterial activities. Combination of above biomaterials with tissue engineering techniques led to the production of a new wound dressing. Therefore, in this study, PRGF was obtained from platelet-rich plasma and a multi-layered scaffold was fabricated by electerospining method using polyurethane (PU) fibers, PRGF and gelatin fibers. Scanning electron microscopy (SEM), tensile and water contact angle tests were performed to assess the characteristics of the scaffolds. The human Adipose Mesenchymal Stem Cells (hAMSCs) were extracted and cultured with the fibroblast cells (HU-02) as co-culture cells and Lactobacillus plantarum was cultured on scaffolds with or without PRGF to evaluate cell viability, toxicity and proliferation, then antibacterial activities of L.plantarum were examined. The result of MTT assay after 14 days indicated that PRFG and L.plantarum had significant positive effect on viability and proliferation of co-culture cells. SEM photograph illustrated adhesion and proliferation of cells and bacteria on scaffolds up to 21 days. The Agar-well diffusion test confirmed the antibacterial effect of L.plantarum on Pseudomonas aeruginosa, Salmonella typhimurium, Staphylococcus aureus, and Escherichia coli with strong inhibition zone. The current multi-layered scaffold provides the appropriate wound dressing for cell adhesion, proliferation and prevents wound infection.
Bahram Ahmadian, Bahman Vahidi,
Volume 13, Issue 4 (1-2023)
Volume 13, Issue 4 (1-2023)
Abstract
Evaluating the response of the stem cells to different mechanical stimulation is an important issue to obtain control over cell behavior in the culture environment. One of the effective parameters in the mechanoregulation of stem cells is the microstructure of scaffolds. Evaluating the effect of microstructure of scaffold in the lab environment is very complicated. Therefore, in this study, the effect of scaffold architecture on mechanical factors in the scaffold was investigated under oscillatory fluid flow by using numerical modeling. In this study, distribution of shear stress and fluid velocity in three types of scaffolds with spherical, cubical and regular hexagonal pores with length of 300, 350, 400, 450 and 500 micrometers were investigated by using computational fluid dynamics method. The results of the computational fluid dynamics model showed that the scaffold with spherical and cubic pores shape with length of 500 micrometers and scaffold with hexagonal pores with length of 450 micrometers experienced shear stress in the range of 0.1-10 mPa. This range of the shear stress is suitable for differentiation of the stem cell to bone cells. Moreover, the result of exerting oscillatory fluid flow to these scaffolds indicated that dead zones of the scaffold, where isn’t suitable for cell seeding, was decreased due to the access of fluid flow to the different area of scaffold. The results of this study can be used in a laboratory to achieve optimal stem cell culture to provide suitable environment culture for differentiation of stem cells toward the bone cell.
Volume 16, Issue 1 (8-2013)
Abstract
Objective: In this study we introduced an RGD-containing peptide of collagen IV origin that possesses potent cell adhesion and proliferation properties. This peptide was immobilized on a nanofibrous polycaprolactone/gelatin scaffold after which we analyzed human bone marrow-derived mesenchymal stem cells (hBMSCs) adhesion and proliferation on this peptide-modified scaffold. Methods: Nanofibrous scaffold was prepared by electrospinning. The peptide was synthesized by solid-phase peptide synthesis and immobilized on electrospun nanofibrous a polycaprolactone/gelatin scaffold by chemical bonding. Native and modified scaffolds were characterized with Scanning Electron Microscope (SEM) and Fourier-Transform Infra-red Spectroscopy (FTIR). Adhesion and proliferation of hBMSCs on native and modified scaffolds were analyzed by the Methylthiazol Tetrazolium (MTT) assay. Results: SEM images showed that electrospun scaffolds had homogenous morphology and were 312±89 nm in diameter. There was no significant difference in scaffold morphology before and after peptide immobilization. FTIR results showed that the peptide was successfully immobilized on the scaffold. Based on MTT assay, cell adhesion studies indicated that peptide immobilization improved cell adhesion on RGD-modified scaffolds at all corresponding time points (pConclusion: This novel peptide and modified nanofibrous scaffold, having improved cell adhesion and proliferation properties, can be used for tissue engineering and regenerative medicine by using hBMSCs.
Volume 17, Issue 9 (11-2017)
Abstract
The use of porous scaffolds for repairing the damaged bone tissues has been increased in recent years. As exploration of the mechanical properties of the scaffolds on the basis of experiments is time consuming and uneconomic, mathematical models are increasingly being introduced into the field, but most of them rely on finite element method and theoretical studies are rarely found in the literature. In this paper, different micromechanical models are presented for obtaining the effective elastic properties of bone scaffolds. Using these models, the mechanical properties of different scaffolds, including ceramic and composite bone scaffolds, are investigated. Single scale and multi-scale modeling approaches are used to simulate the ceramic and composite scaffolds, respectively. Furthermore, because of the wide application of hydroxyapatite in fabrication of bone scaffolds, the mechanical properties of hydroxyapatite scaffolds in different porosities are obtained in the current study by means of the presented methods. Results show that Dewey, self-consistent and differential schemes are the best methods in calculation of the value of Young’s modulus of these scaffolds in porosity ranges of less than 30 %, 30 to 60 % and more than 60 %, respectively. Moreover, self-consistent scheme gives good estimation of the value of Poisson’s ratio of hydroxyapatite scaffolds in different porosities. By obtaining the values of the mechanical properties of the scaffolds in different porosities by these models and using the statistical analysis, the mathematical relationship between the porosity and the mechanical properties of this kind of scaffolds (Young’s modulus and Poisson’s ratio) is obtained.
Volume 17, Issue 12 (2-2018)
Abstract
The main purpose of using scaffolds replacement tissues of the body. The most important part is to choose the type and steel scaffolding so that eventually will replace the damaged tissue. One of the mechanisms proposed to reshape the bone is based on its piezoelectric properties. It seems that the use of piezoelectric materials is an option for use in the body, is a unique privilege. Therefore, the ceramic barium titanate (BaTiO3) having good piezoelectric properties, Curie temperature of about 125˚C and laboratory observations that non-toxic in the body, as a candidate to replace and simulate the performance of bone tissue, has been proposed. In this study, the design and produce of barium titanate piezoelectric ceramic as a bone scaffold with foam casting method and become coated with gelatinous and nanostructured HA composite for bone tissue engineering. Then test its properties by infrared spectroscopy, X-ray diffraction, scanning electron microscopy and mechanical properties were studied. In the end, it was concluded that the barium titanate scaffold produse with foam casting method coated with gelatin nano hydroxyapatite composite structure suitable for use in bone tissue engineering.
Volume 18, Issue 4 (1-2016)
Abstract
In recent years, electrospinning that has the capability to form polymeric nano-/microfibers has gained substantial attention for fabrication of tissue engineering scaffolds. The morphological resemblance to native extracellular matrix (ECM), high surface to volume ratio, high porosity, and pore interconnectivity are amongst the brilliant features of electrospun structures. The high surface area to volume ratio and interconnected pores of these fibrous meshes confer desirable cell attachment and growth. However, due to small pore sizes and high packing density of electrospun nanofibers, cell penetration into a conventional electrospun mat is completely restrained. Scarce cell infiltration in turn prohibit cell migration into internal parts of the scaffold, cause inhomogeneous cell distribution throughout the structure, limit vascularization, and impede tissue ingrowth. In fact, traditional electrospun nanofibrous scaffolds in practice act as two-dimensional (2D) surfaces rather than three-dimensional (3D) microenvironments. Thus far, a number of approaches have been employed to solve this problem, which range from simple variations in electrospinning parameters to intricate post-processing modifications. Some efforts directly manipulate the electrospun mat characteristics to enhance cell penetration, while others combine cells with scaffolds or encourage cells to migrate into internal parts with different stimuli. In the present study, we have attempted to provide an overview of different approaches offered for improving cell infiltration in electrospun scaffolds.
Volume 19, Issue 1 (5-2016)
Abstract
Objective: In the present study we investigated the effect of a dynamic culture in a shake flask bioreactor (SFB) on the proliferation and differentiation to osteoblasts for human mesenchymal stem cells (hMSCs) cultured on multilayered electrospun PCL-nHA scaffolds.
Methods: First, we prepared PCL-nHA scaffolds by electrospinning. After culturing the hMSCs on the scaffolds in a static state, the seeded scaffolds were divided into two groups (static and SFB culture) and incubated up to 21 days. We assessed biocompatibility and cell differentiation by the MTT, calcium, and alkaline phosphatase (ALP) assays on days 7, 14, and 21.
Results: The MTT assay evaluated hMSCs proliferation rate on the scaffold layers. There was greater cell proliferation (optical density values) on the layers in the bioreactor (OD=2.18) compared to the static state condition (OD=1.68) on day 21. In order to study osteogenic differentiation, we determined the amount of calcium deposition and ALP activity. We observed a 1.6-fold greater level of calcium deposition for the dynamic culture compared to the static culture, which showed increased cell differentiation within the bioreactor on day 21. The ALP results showed that during 14 days, ALP activity within the bioreactor was 1.55-fold higher than the static culture.
Conclusion: The SFB culture displayed a higher proliferation and differentiation of stem cells on PCL-nHA multilayered scaffolds compared to the static state condition.
Volume 20, Issue 2 (8-2017)
Abstract
Objective: Tissue engineering, as an interdisciplinary field, assists cell therapy by using scaffolds, cells, and growth factors since 30 years ago. Cells isolated from the body should be supported by a scaffold which could mimic the function and structure of natural extracellular matrix (ECM). To accomplish this goal, we have fabricated and characterized synthetic wet electrospun poly(lactic) acid (PLA) scaffolds.
Methods: ThePLA polymer was used at various concentrations (10%, 13%, 15%, 17%, 20% w/v) with a novel architecture produced by a wet-electrospinning process for tissue engineering applications. In the wet electrospinning method, we used an aqueous solution of sodium hydroxide (NaOH) as the coagulation bath. Then, we characterized the biocompatibility and morphology of these scaffolds by the MTT assay and SEM, respectively.
Results: The data collected from the characterization of scaffolds and in vitro human Wharton’s jelly-derived stem cells/scaffold culture showed that the 15% w/v of PLA with high porosity was the best polymer concentration in terms of cell attachment and proliferation.
Conclusion:Electrospinning PLA at the 10% or 20% w/v concentrations was difficult. Additionally, they could not provide a favorable matrix for cell proliferation and attachment. However, the results have suggested that the novel nanofiber fabrication system would be very useful for the structure control of 3D nanofiber fabrics.
Volume 20, Issue 2 (8-2017)
Abstract
Synthetic biomaterials are currently used as bone graft substitutes to treat bone disorders. Based on biomechanical properties, these biomaterials are selected to engineer bioactive and bioresorbable scaffolds that increase tissue ingrowth. These porous scaffolds play an important role in new bone formation and vascularization with the ability to incorporate genes, drugs, growth factors, and stem cells. This review focuses on recent advances on bioactive glass materials for bone regeneration. Despite inherent brittleness, bioactive glasses have many promising characteristics for bone engineering scaffolds. Compared to silicate bioactive glasses, borate and borosilicate have the ability to enhance new bone formation .These materials have controllable degradation rates that closely match new bone formation. Interestingly, bioactive glasses can be doped with elements such as Cu, Zn, and Sr, which are advantageous for healthy bone growth. Although bioactive glasses have been examined in detail for bone repair, few investigations have been performed on their applications for repair of soft tissues. A recent work has shown bioactive glass has the ability to promote angiogenesis for healing of soft tissue wounds.
In this review, we highlight current advances in the use of bioactive glass materials and their conversion into scaffolds with the essential anatomical shape. Methods used to manipulate the materials’ structures in bone tissue engineering applications and growth factors involved in bone regeneration will be briefly discussed.
Volume 21, Issue 2 (7-2018)
Abstract
Introduction: Myocardium tissue is an electroactive tissue capable of transferring electrical signals, which lead to synchronized beating of heart. Electrical impulses originate from sinoatrial node and spread though myocardium to induce mechanical contraction of cardiomyocytes. As the leading cause of death, worldwide, cardiovascular diseases are often accompanied by disruption of electrical integrity of cardiac tissue and arrhythmia. In many arrhythmias, lack of conduction as well as unidirectional conduction result in insufficient intercellular electrical coupling at gap junctions. Due to limitation of conventional treatment methods such as heart transplantation, pathological and therapeutic researches in cardiac electrical disorders have increased in last few years. The aim of this study was to review the last studies in electrical system of heart and its disorder along with the results and the future of the cardiovascular tissue therapy method based on Conductive biomaterial.
Conclusion: Electrical integrity is essential for normal functioning of the heart. Among the new methods of treating heart failure and improving the electrical integrity of the disorder caused by these defects, tissue engineering with the use of conductive electrical conductive materials has been widely considered along with other methods. Three main types of conductive materials have been used for tissue engineering application: (1) Gold-based materials (2) Carbon-based materials (3) Conductive polymers.
Conclusion: Electrical integrity is essential for normal functioning of the heart. Among the new methods of treating heart failure and improving the electrical integrity of the disorder caused by these defects, tissue engineering with the use of conductive electrical conductive materials has been widely considered along with other methods. Three main types of conductive materials have been used for tissue engineering application: (1) Gold-based materials (2) Carbon-based materials (3) Conductive polymers.
Volume 21, Issue 2 (1-2021)
Abstract
Memory-shaped polymers are thermally induced subsets of intelligent materials that require thermomechanical behavior to accurately understand their function. In this study, polymeric memory scaffolds were fabricated using polylactic acid by molten labeling method in three reticular honeycomb, rhombic and elliptical form. Parameters such as longitudinal dimensions and wall thickness of printed scaffolds compared to the designed scaffolds and solutions were presented to enhance the printing accuracy. Built-in scaffolds can be a good option for stent use. Formal memory properties experiments with 30% axial strain were performed to study the shape memory behavior of polymer on scaffolds. The results showed that the percentage of shape recovery in scaffolds with symmetric angular grid networks was higher than elliptical reticular stents. The minimum percentage of longitudinal recovery belonged to the elliptical reticular stent and was 74.5%. The percentage of longitudinal recovery of honeycomb and rhododendron reticular stents is approximately equal to 80.3%. The results of this study can be used to optimize the stent grid geometry to increase the retrieval force to resolving vascular clogging.