Designing and synthesis of injectable hydrogel based on carboxymethyl cellulose/carboxymethyl chitosan containing QK peptide for femoral head osteonecrosis healing.

Femoral head necrosis is a debilitating disorder that typically caused by impaired blood supply to the hip joint. In this study, a novel injectable hydrogel based on Oxidized Carboxymethyl Cellulose (OCMC)-Carboxymethyl Chitosan (CMCS) polymers containing an angiogenesis stimulator peptide (QK) with a non-toxic crosslinking interaction (Schiff based reaction) was synthesized to enhance angiogenesis following femoral head necrosis in an animal model. The physicochemical features of fabricated injectable hydrogel were analyzed by FTIR, swelling and degradation rate, rheometry, and peptide release. Also, the safety and efficacy were evaluated following an in vitro hydrogel injection study and an avascular necrosis (AVN) animal model. According to the results, the hydrogel exhibited an appropriate swelling ratio and water uptake (>90 %, 24 h) as well as a suitable degradation rate over 21 days accompanied by a continuous peptide release. Also, data showed that hydrogels containing QK peptide boosted the proliferation, differentiation, angiogenesis, and osteogenic potential of both Bone Marrow mesenchymal Stem Cells (BM-MSCs) and human umbilical vein endothelial cells (HUVECs) (****p < 0.0001 and ***p < 0.001, respectively). Furthermore, molecular and histological evaluations significantly demonstrated the overexpression of Runx2, Osteocalcin, Collagen I, VEGF and CD34 genes (**p < 0.01 and ***p < 0.001, respectively), and also femoral head necrosis was effectively prohibited, and more blood vessels were detected in defect area by OCMC-CMCS hydrogel containing QK peptide (bone trabeculae >9000, ***p < 0.001). In conclusion, the findings demonstrate that OCMC-CMCS-QK injectable hydrogel could be considered as an impressive therapeutic construct for femoral head AVN healing.

3D-printed polycaprolactone/tricalcium silicate scaffolds modified with decellularized bone ECM-oxidized alginate for bone tissue engineering.

The treatment of large craniofacial bone defects requires more advanced and effective strategies than bone grafts since such defects are challenging and cannot heal without intervention. In this regard, 3D printing offers promising solutions through the fabrication of scaffolds with the required shape, porosity, and various biomaterials suitable for specific tissues. In this study, 3D-printed polycaprolactone (PCL)-based scaffolds containing up to 30 % tricalcium silicate (TCS) were fabricated and then modified by incorporation of decellularized bone matrix- oxidized sodium alginate (DBM-OA). The results showed that the addition of 20 % TCS increased compressive modulus by 4.5-fold, yield strength by 12-fold, and toughness by 15-fold compared to pure PCL. In addition, the samples containing TCS revealed the formation of crystalline phases with a Ca/P ratio near that of hydroxyapatite (1.67). Cellular experiment results demonstrated that TCS have improved the biocompatibility of PCL-based scaffolds. On day 7, the scaffolds modified with DBM and 20 % TCS exhibited 8-fold enhancement of ALP activity of placenta-derived mesenchymal stem/stromal cells (P-MSCs) compared to pure PCL scaffolds. The present study's results suggest that the incorporation of TCS and DBM-OA into the PCL-based scaffold improves its mechanical behavior, bioactivity, biocompatibility, and promotes mineralization and early osteogenic activity.

Recent advances in soluble decellularized extracellular matrix for heart tissue engineering and organ modeling.

Despite the advent of tissue engineering (TE) for the remodeling, restoring, and replacing damaged cardiovascular tissues, the progress is hindered by the optimal mechanical and chemical properties required to induce cardiac tissue-specific cellular behaviors including migration, adhesion, proliferation, and differentiation. Cardiac extracellular matrix (ECM) consists of numerous structural and functional molecules and tissue-specific cells, therefore it plays an important role in stimulating cell proliferation and differentiation, guiding cell migration, and activating regulatory signaling pathways. With the improvement and modification of cell removal methods, decellularized ECM (dECM) preserves biochemical complexity, and bio-inductive properties of the native matrix and improves the process of generating functional tissue. In this review, we first provide an overview of the latest advancements in the utilization of dECM in in vitro model systems for disease and tissue modeling, as well as drug screening. Then, we explore the role of dECM-based biomaterials in cardiovascular regenerative medicine (RM), including both invasive and non-invasive methods. In the next step, we elucidate the engineering and material considerations in the preparation of dECM-based biomaterials, namely various decellularization techniques, dECM sources, modulation, characterizations, and fabrication approaches. Finally, we discuss the limitations and future directions in fabrication of dECM-based biomaterials for cardiovascular modeling, RM, and clinical translation.

Inflammation and Mental Health Disorders: Immunomodulation as a Potential Therapy for Psychiatric Conditions.

Mood disorders are the leading cause of disability worldwide and their incidence has significantly increased after the COVID-19 pandemic. Despite the continuous surge in the number of people diagnosed with psychiatric disorders, the treatment methods for these conditions remain limited. A significant number of people either do not respond to therapy or discontinue the drugs due to their severe side effects. Therefore, alternative therapeutic interventions are needed. Previous studies have shown a correlation between immunological alterations and the occurrence of mental health disorders, yet immunomodulatory therapies have been barely investigated for combating psychiatric conditions. In this article, we have reviewed the immunological alterations that occur during the onset of mental health disorders, including microglial activation, an increased number of circulating innate immune cells, reduced activity of natural killer cells, altered T cell morphology and functionality, and an increased secretion of pro-inflammatory cytokines. This article also examines key studies that demonstrate the therapeutic efficacy of anti-inflammatory medications in mental health disorders. These studies suggest that immunomodulation can potentially be used as a complementary therapy for controlling psychiatric conditions after careful screening of candidate drugs and consideration of their efficacy and side effects in clinical trials.

Formulation and Characterization of a Novel Oxidized Alginate-Gelatin-Silk Fibroin Bioink with the Aim of Skin Regeneration.

Background: In the present study, a novel bioink was suggested based on the oxidized alginate (OAlg), gelatin (GL), and silk fibroin (SF) hydrogels. Methods: The composition of the bioink was optimized by the rheological and printability measurements, and the extrusion-based 3D bioprinting process was performed by applying the optimum OAlg-based bioink. Results: The results demonstrated that the viscosity of bioink was continuously decreased by increasing the SF/GL ratio, and the bioink displayed a maximum achievable printability (92 ± 2%) at 2% (w/v) of SF and 4% (w/v) of GL. Moreover, the cellular behavior of the scaffolds investigated by MTT assay and live/dead staining confirmed the biocompatibility of the prepared bioink. Conclusion: The bioprinted OAlg-GL-SF scaffold could have the potential for using in skin tissue engineering applications, which needs further exploration.

Adsorption and encapsulation of melittin on covalently functionalized carbon nanotubes; a molecular dynamics simulation study.

For the first time, molecular dynamics (MD) simulation was used to examine melittin's adsorption and encapsulation on covalently functionalized carbon nanotubes (fCNTs). The CNT wall and terminals were functionalized with carboxy, hydroxyl, and amine functional groups. The findings demonstrated that the melittin would be adsorbed on the fCNT's outer surface when just the CNT terminal is functionalized. On the other hand, melittin is encapsulated inside the nanotube space when the CNTs' walls and terminals are functionalized. Encapsulated melittin has an alpha-helix structure similar to melittin in a water medium. With the use of parameters like root mean square fluctuations (RMSF) and radius of gyration (Rg), the melittin conformational changes were evaluated. According to the findings, the amine functional group significantly alters the melittin's conformation. The wall and terminals fCNTs with hydroxyl and carboxyl could encapsulate melittin inside them with a stable structure. This result will be useful for the design of peptide carriers.

Targeting reactive astrocytes by pH-responsive ligand-bonded polymeric nanoparticles in spinal cord injury.

In spinal cord injuries, axonal regeneration decreases with the activation of astrocytes followed by glial scar formation. Targeting reactive astrocytes has been recently performed by unsafe viral vectors to inhibit gliosis. In the current study, biocompatible polymeric nanoparticles were selected as an alternative for viruses to target reactive astrocytes for further drug/gene delivery applications. Lipopolysaccharide-bonded chitosan-quantum dots/poly acrylic acid nanoparticles were prepared by ionic gelation method to target reactive astrocytes both in vitro and in spinal cord-injured rats. Owing to their biocompatibility and pH-responsive behavior, chitosan and poly acrylic acid were the main components of nanoparticles. Nanoparticles were then chemically labeled with quantum dots to track the cell uptake and electrostatically interacted with lipopolysaccharide as a targeting ligand. In vitro and in vivo studies were performed in triplicate and all data were expressed as the mean ± the standard error of the mean. Smart nanoparticles with optimum size (61.9 nm) and surface charge (+ 12.5 mV) successfully targeted primary reactive astrocytes extracted from the rat cerebral cortex. In vitro studies represented high cell viability (96%) in the exposure of biocompatible nanoparticles. The pH-responsive behavior of nanoparticles was proved by their internalization into the cell's nuclei due to the swelling and endosomal escape of nanoparticles in acidic pH. In vivo studies demonstrated higher transfection of nanoparticles into reactive astrocytes compared to the neurons. pH-responsive ligand-bonded chitosan-based nanoparticles are good alternatives for viral vectors in targeted delivery applications for the treatment of spinal cord injuries.

A hybrid cartilage extracellular matrix-based hydrogel/poly (ε-caprolactone) scaffold incorporated with Kartogenin for cartilage tissue engineering.

Despite extensive studies, hydrogels are unable to meet the mechanical and biological requirements for successful outcomes in cartilage tissue engineering. In the present study, beta cyclodextrin (ß-CD)-modified alginate/cartilage extracellular matrix (ECM)-based interpenetrating polymer network (IPN) hydrogel was developed for sustained release of Kartogenin (KGN). Furthermore, the hydrogel was incorporated within a 3D-printed poly (ε-caprolactone) (PCL)/starch microfiber network in order to reinforce the construct for cartilage tissue engineering. All the synthesized compounds were characterized by H1-NMR spectroscopy. The hydrogel/microfiber composite with a microfiber strand size and strand spacing of 300 µm and 2 mm, respectively showed a compressive modulus of 17.2 MPa, resembling the properties of the native cartilage tissue. Considering water uptake capacity, degradation rate, mechanical property, cell cytotoxicity and glycosaminoglycan secretions, ß-CD-modified hydrogel reinforced with printed PCL/starch microfibers with controlled release of KGN may be considered as a promising candidate for using in articular cartilage defects.

Chemical modification of hyaluronic acid improves its supportive action on embryo implantation.

Hyaluronic acid (HA) is a supplement of the embryo transfer medium that improves embryo implantation. We have suggested that the supportive action of HA can be promoted by introducing additional artificial binding sites on the HA structure. HA was modified at carboxyl sites separately with thiol (SH) and N-hydroxysuccinimide (NHS), as mucoadhesive and amine-reactive groups, respectively. The mouse blastocysts were incubated with HA derivatives for 15 min. The HA coatings maintained their potential for enzymatic degradation and showed no detrimental effect on embryonic viability and developmental potential. After in vivo transfer, a significantly higher implantation rate was attained by HA-NHS treatment (80 %) compared with the HA-SH (53 %) and the commercial transfer medium, EmbryoGlue® (56 %). The HA-NHS was produced by a slight modification on the native structure of HA using a simple, fast, non-expensive and scalable chemistry which all promise applicability of this new HA derivative in assisted reproductive technologies.

Alginate/cartilage extracellular matrix-based injectable interpenetrating polymer network hydrogel for cartilage tissue engineering.

In the present study, alginate/cartilage extracellular matrix (ECM)-based injectable hydrogel was developed incorporated with silk fibroin nanofibers (SFN) for cartilage tissue engineering. The in situ forming hydrogels were composed of different ionic crosslinked alginate concentrations with 1% w/v enzymatically crosslinked phenolized cartilage ECM, resulting in an interpenetrating polymer network (IPN). The response surface methodology (RSM) approach was applied to optimize IPN hydrogel's mechanical properties by varying alginate and SFN concentrations. The results demonstrated that upon increasing the alginate concentration, the compression modulus improved. The SFN concentration was optimized to reach a desired mechanical stiffness. Accordingly, the concentrations of alginate and SFN to have an optimum compression modulus in the hydrogel were found to be 1.685 and 1.724% w/v, respectively. The gelation time was found to be about 10 s for all the samples. Scanning electron microscope (SEM) images showed homogeneous dispersion of the SFN in the hydrogel, mimicking the natural cartilage environment. Furthermore, water uptake capacity, degradation rate, cell cytotoxicity, and glycosaminoglycan and collagen II secretions were determined for the optimum hydrogel to support its potential as an injectable scaffold for articular cartilage defects.

Fabrication and characterization of an injectable reinforced composite scaffold for cartilage tissue engineering: an in vitro study.

There are limitations in current medications of articular cartilage injuries. Although injectable bioactive hydrogels are promising options, they have decreased biomechanical performance. Researchers should consider many factors when providing solutions to overcome these challenges. In this study, we created an injectable composite hydrogel from chitosan and human acellular cartilage extracellular matrix (ECM) particles. In order to enhance its mechanical properties, we reinforced this hydrogel with microporous microspheres composed of the same materials as the structural building blocks of the scaffold. Articular cartilage from human donors was decellularized by a combination of physical, chemical, and enzymatic methods. The decellularization efficiency was assessed by histological analysis and assessment of DNA content. We characterized the composite constructs in terms of storage modulus, gelation time, biocompatibility, and differentiation potential. The results showed that mechanical behavior increased with an increase in microsphere content. The sample that contained 10% microsphere had an enhanced storage modulus of up to 90 kPa. Biocompatibility and preliminary differentiation investigations revealed that this composite hydrogel might have potential benefits for cartilage tissue engineering.

Biohybrid oxidized alginate/myocardial extracellular matrix injectable hydrogels with improved electromechanical properties for cardiac tissue engineering.

Injectable hydrogels which mimic the physicochemical and electromechanical properties of cardiac tissue is advantageous for cardiac tissue engineering. Here, a newly-developed in situ forming double-network hydrogel derived from biological macromolecules (oxidized alginate (OA) and myocardial extracellular matrix (ECM)) with improved mechanical properties and electrical conductivity was optimized. 3-(2-aminoethyl amino) propyltrimethoxysilane (APTMS)-functionalized reduced graphene oxide (Amine-rGO) was added to this system with varied concentrations to promote electromechanical properties of the hydrogel. Alginate was partially oxidized with an oxidation degree of 5% and the resulting OA was cross-linked via calcium ions which was reacted with amine groups of ECM and Amine-rGO through Schiff-base reaction. In situ forming hydrogels composed of 4% w/v OA and 0.8% w/v ECM showed appropriate gelation time and tensile Young's modulus. The electroactive hydrogels showed electrical conductivity in the range of semi-conductors and a suitable biodegradation profile for cardiac tissue engineering. Cytocompatibility analysis was performed by MTT assay against human umbilical vein endothelial cells (HUVECs), and the optimal hydrogel with 25 µg/ml concentration of Amine-rGO showed higher cell viability than that for other samples. The results of this study present the potential of OA/myocardial ECM-based hydrogel incorporated with Amine-rGO to provide a desirable platform for cardiac tissue engineering.

Effect of Physico-Chemical Properties of Nanoparticles on Their Intracellular Uptake.

Cellular internalization of inorganic, lipidic and polymeric nanoparticles is of great significance in the quest to develop effective formulations for the treatment of high morbidity rate diseases. Understanding nanoparticle-cell interactions plays a key role in therapeutic interventions, and it continues to be a topic of great interest to both chemists and biologists. The mechanistic evaluation of cellular uptake is quite complex and is continuously being aided by the design of nanocarriers with desired physico-chemical properties. The progress in biomedicine, including enhancing the rate of uptake by the cells, is being made through the development of structure-property relationships in nanoparticles. We summarize here investigations related to transport pathways through active and passive mechanisms, and the role played by physico-chemical properties of nanoparticles, including size, geometry or shape, core-corona structure, surface chemistry, ligand binding and mechanical effects, in influencing intracellular delivery. It is becoming clear that designing nanoparticles with specific surface composition, and engineered physical and mechanical characteristics, can facilitate their internalization more efficiently into the targeted cells, as well as enhance the rate of cellular uptake.

Bioengineering Approaches for Corneal Regenerative Medicine.

BACKGROUND: Since the cornea is responsible for transmitting and focusing light into the eye, injury or pathology affecting any layer of the cornea can cause a detrimental effect on visual acuity. Aging is also a reason for corneal degeneration. Depending on the level of the injury, conservative therapies and donor tissue transplantation are the most common treatments for corneal diseases. Not only is there a lack of donor tissue and risk of infection/rejection, but the inherent ability of corneal cells and layers to regenerate has led to research in regenerative approaches and treatments. METHODS: In this review, we first discussed the anatomy of the cornea and the required properties for reconstructing layers of the cornea. Regenerative approaches are divided into two main categories; using direct cell/growth factor delivery or using scaffold-based cell delivery. It is expected delivered cells migrate and integrate into the host tissue and restore its structure and function to restore vision. Growth factor delivery also has shown promising results for corneal surface regeneration. Scaffold-based approaches are categorized based on the type of scaffold, since it has a significant impact on the efficiency of regeneration, into the hydrogel and non-hydrogel based scaffolds. Various types of cells, biomaterials, and techniques are well covered. RESULTS: The most important characteristics to be considered for biomaterials in corneal regeneration are suitable mechanical properties, biocompatibility, biodegradability, and transparency. Moreover, a curved shape structure and spatial arrangement of the fibrils have been shown to mimic the corneal extracellular matrix for cells and enhance cell differentiation. CONCLUSION: Tissue engineering and regenerative medicine approaches showed to have promising outcomes for corneal regeneration. However, besides proper mechanical and optical properties, other factors such as appropriate sterilization method, storage, shelf life and etc. should be taken into account in order to develop an engineered cornea for clinical trials.

Bioinspired Nanofiber Scaffold for Differentiating Bone Marrow-Derived Neural Stem Cells to Oligodendrocyte-Like Cells: Design, Fabrication, and Characterization.

BACKGROUND: Researchers are trying to study the mechanism of neural stem cells (NSCs) differentiation to oligodendrocyte-like cells (OLCs) as well as to enhance the selective differentiation of NSCs to oligodendrocytes. However, the limitation in nerve tissue accessibility to isolate the NSCs as well as their differentiation toward oligodendrocytes is still challenging. PURPOSE: In the present study, a hybrid polycaprolactone (PCL)-gelatin nanofiber scaffold mimicking the native extracellular matrix and axon morphology to direct the differentiation of bone marrow-derived NSCs to OLCs was introduced. MATERIALS AND METHODS: In order to achieve a sustained release of T3, this factor was encapsulated within chitosan nanoparticles and chitosan-loaded T3 was incorporated within PCL nanofibers. Polyaniline graphene (PAG) nanocomposite was incorporated within gelatin nanofibers to endow the scaffold with conductive properties, which resemble the conductive behavior of axons. Biodegradation, water contact angle measurements, and scanning electron microscopy (SEM) observations as well as conductivity tests were used to evaluate the properties of the prepared scaffold. The concentration of PAG and T3-loaded chitosan NPs in nanofibers were optimized by examining the proliferation of cultured bone marrow-derived mesenchymal stem cells (BMSCs) on the scaffolds. The differentiation of BMSCs-derived NSCs cultured on the fabricated scaffolds into OLCs was analyzed by evaluating the expression of oligodendrocyte markers using immunofluorescence (ICC), RT-PCR and flowcytometric assays. RESULTS: Incorporating 2% PAG proved to have superior cell support and proliferation while guaranteeing electrical conductivity of 10.8 × 10-5 S/cm. Moreover, the scaffold containing 2% of T3-loaded chitosan NPs was considered to be the most biocompatible samples. Result of ICC, RT-PCR and flow cytometry showed high expression of O4, Olig2, platelet-derived growth factor receptor-alpha (PDGFR-α), O1, myelin/oligodendrocyte glycoprotein (MOG) and myelin basic protein (MBP) high expressed but low expression of glial fibrillary acidic protein (GFAP). CONCLUSION: Considering surface topography, biocompatibility, electrical conductivity and gene expression, the hybrid PCL/gelatin scaffold with the controlled release of T3 may be considered as a promising candidate to be used as an in vitro model to study patient-derived oligodendrocytes by isolating patient's BMSCs in pathological conditions such as diseases or injuries. Moreover, the resulted oligodendrocytes can be used as a desirable source for transplanting in patients.

Stereolithography 3D Bioprinting Method for Fabrication of Human Corneal Stroma Equivalent.

3D bioprinting technology is a promising approach for corneal stromal tissue regeneration. In this study, gelatin methacrylate (GelMA) mixed with corneal stromal cells was used as a bioink. The visible light-based stereolithography (SLA) 3D bioprinting method was utilized to print the anatomically similar dome-shaped structure of the human corneal stroma. Two different concentrations of GelMA macromer (7.5 and 12.5%) were tested for corneal stroma bioprinting. Due to high macromer concentrations, 12.5% GelMA was stiffer than 7.5% GelMA, which made it easier to handle. In terms of water content and optical transmittance of the bioprinted scaffolds, we observed that scaffold with 12.5% GelMA concentration was closer to the native corneal stroma tissue. Subsequently, cell proliferation, gene and protein expression of human corneal stromal cells encapsulated in the bioprinted scaffolds were investigated. Cytocompatibility in 12.5% GelMA scaffolds was observed to be 81.86 and 156.11% at day 1 and 7, respectively, which were significantly higher than those in 7.5% GelMA scaffolds. Elongated corneal stromal cells were observed in 12.5% GelMA samples after 7 days, indicating the cell attachment, growth, and integration within the scaffold. The gene expression of collagen type I, lumican and keratan sulfate increased over time for the cells cultured in 12.5% GelMA scaffolds as compared to those cultured on the plastic tissue culture plate. The expression of collagen type I and lumican were also visualized using immunohistochemistry after 28 days. These findings imply that the SLA 3D bioprinting method with GelMA hydrogel bioinks is a promising approach for corneal stroma tissue biofabrication.

Induced cell migration based on a bioactive hydrogel sheet combined with a perfused microfluidic system.

Endothelial cell migration is a crucial step in the process of new blood vessel formation-a necessary process to maintain cell viability inside thick tissue constructs. Here, we report a new method for maintaining cell viability and inducing cell migration using a perfused microfluidic platform based on collagen gel and a gradient hydrogel sheet. Due to the helpful role of the extracellular matrix components in cell viability, we developed a hydrogel sheet from decellularized tissue (DT) of the bovine heart and chitosan (CS). The results showed that hydrogel sheets with an optimum weight ratio of CS/DT = 2 possess a porosity of around 75%, a mechanical strength of 23 kPa, and display cell viability up to 78%. Then, we immobilized a radial gradient of vascular endothelial growth factor (VEGF) on the hydrogel sheet to promote human umbilical vein endothelial cell migration. Finally, we incorporated the whole system as an entirety on the top of the microfluidic platform and studied cell migration through the hydrogel sheet in the presence of soluble and immobilized VEGF. The results demonstrated that immobilized VEGF stimulated cell migration in the hydrogel sheet at all depths compared with soluble VEGF. The results also showed that applying a VEGF gradient in both soluble and immobilized states had a significant effect on cell migration at limited depths (<100 µm). The main finding of this study is a significant improvement in cell migration using an in vivo imitating, cost-efficient and highly reproducible platform, which may open up a new perspective for tissue engineering applications.

The Controlled Release of Dexamethasone Sodium Phosphate from Bioactive Electrospun PCL/Gelatin Nanofiber Scaffold.

In this study, a system of dexamethasone sodium phosphate (DEXP)-loaded chitosan nanoparticles embedded in poly-ε-caprolacton (PCL) and gelatin electrospun nanofiber scaffold was introduced with potential therapeutic application for treatment of the nervous system. Besides anti-inflammatory properties, DEXP act through its glucocorticoid receptors, which are involved in the inhibition of astrocyte proliferation and microglial activation. Bovine serum albumin (BSA) was used to improve the encapsulation efficiency of DEXP within chitosan nanoparticles and to overcome its initial burst release. BSA incorporation within the chitosan nanoparticles increased the encapsulation efficiency of DEXP from 30% to 77%. The comparison between DEXP release profile from PCL/gelatin scaffold with and without chitosan nanoparticles revealed that the system of DEXP-BSA-loaded chitosan nanoparticles embedded in electrospun PCL nanofiber scaffold provided a more controlled release pattern of the loaded drug. The scaffolds properties in terms of structure, hydrophilicity, cell compatibility, mechanical property, and biodegradability were further investigated, which might show its potential application for the repair of spinal cord injury.

An optimized procedure to develop a 3-dimensional microfluidic hydrogel with parallel transport networks.

The development of microfluidic hydrogels is an attractive method to generate continuous perfusion, induce vascularization, increase solute delivery, and ultimately improve cell viability. However, the transport processes in many in vitro studies still have not been realized completely. To address this problem, we have developed a microchanneled hydrogel with different collagen type I concentrations of 1, 2, and 3 wt% and assessed its physical properties and obtained diffusion coefficient of nutrient within the hydrogel. It is well known that microchannel geometry has critical role in maintaining stable perfusion rate. Therefore, in this study, a computational modeling was applied to simulate the 3D microfluidic hydrogel and study the effect of geometric parameters such as microchannel diameters and their distance on the nutrient diffusion. The simulation results showed that the sample with 3 channels with a diameter of 300 µm has adequate diffusion rates and efficiency (56%). Moreover, this system provides easy control and continuous perfusion rate during 5 days of cell culturing. The simulation results were compared with experimental data, and a good correlation was observed for nutrient profiles and cell viability across the hydrogel.

Fabrication, modeling and optimization of lyophilized advanced platelet rich fibrin in combination with collagen-chitosan as a guided bone regeneration membrane.

In this study, lyophilized advanced platelet rich fibrin (A-PRF) was used in combination with collagen-chitosan membrane for the first time to combine advantages of both collagen and A-PRF membranes. Response surface methodology (RSM) was used to design the experimental condition and to correlate the effects of parameters, including chitosan/collagen (chit/col) weight ratio and A-PRF concentration on Young's modulus, mesenchymal stem cell (MSCs) viability and degradation rate of the membranes. Results showed that Young's modulus of the membranes was intensified by increasing chit/col weight ratio and decreasing A-PRF concentration from 3 to 8 MPa. Cell viability of MSCs was improved by both increasing chit/col weight ratio and A-PRF concentration. Moreover, as chit/col weight ratio increased from 0 to 4 and A-PRF concentration decreased from 5 to 0, degradation rate of the membranes decreased from 90 to 20% after four weeks incubation. Finally, based on Design Expert Software calculation for minimizing the degradation rate and maximizing both Young's modulus and cell viability, the values of chit/col weight ratio and A-PRF concentration were suggested to be 4 and 0.58 mg/ml, respectively. Alkaline phosphatase (ALP) activity analysis showed that the addition of A-PRF caused higher osteogenic differentiation.