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PubMed2006

Fabrication and evaluation of porous 2,3-dialdehydecellulose membrane as a potential biodegradable tissue-engineering scaffold.

A simple, novel method to produce porous 2,3-dialdehydecellulose (DAC) membranes as a potential tissue-engineering scaffold has been developed from methylolcellulose by the simultaneous water-induced phase separation and sodium chloride salt leaching techniques, followed by oxidation with sodium periodate in water. Membrane pores increased in size with increasing weight or particle size of the sodium chloride salt. The porosity of the membrane was not affected by the salt particle size, but it increased with an increase in the salt weight to 60%. At higher salt weight percentages, no significant change in the membrane porosity was observed. The oxidation step had no effect on the membrane porosity or pore size. All membranes with a porosity value ranging between 87 and 93% showed interconnected porous structures. The use of these membranes as a potential tissue-engineering scaffold was evaluated with the use of human neonatal skin fibroblast cells. Confocal microscopy showed cell attachment and spreading on these membranes. Immunohistochemical tests revealed the presence of collagen type III and fibronectin, indicating that the cells were viable and formed the extracellular matrix. In conclusion, the DAC membrane supports cell adhesion and proliferation and hence shows potential to be used as a tissue-engineering scaffold.

Absorbable Implants↗

PubMed2005

[Repair of peripheral nerve gap with the use of tissue engineering scaffold complex].

OBJECTIVE: To study the feasibility to repair the peripheral nerve gap with tissue engineering scaffold complex that is composed of medical biodegradable material agarose hydrogel and nerve growth factor (NGF). METHODS: Chitosan tube containing agarose hydrogel and NGF was transplanted to bridge a 10 mm gap of injured sciatic nerve in rat. Chitosan duct without agarose hydrogel and NGF was used as negative control, while autograft nerve as positive control. Sixteen weeks after operation, the regeneration of nerve fiber was observed with morphological and immunohistochemistrical methods. RESULT: The number and diameter of regenerating nerve fibers bridged by the scaffold complex of agarose hydrogel and NGF were better than negative control group (P < 0.01) and reached the level of autograft nerve group. CONCLUSIONS: The new type of tissue engineering scaffold complex of agarose hydrogel and NGF may provide a microenvironment, as well as autograft nerve, to promote nerve regeneration. This technique may benefit patients with nerve injury in the future.

Absorbable Implants↗

PubMed2004

Novel biodegradable electrospun membrane: scaffold for tissue engineering.

Nonwoven fibrous matrixes have been widely used as scaffolds in tissue engineering, and modification of microstructure of these matrices is needed to organize cells in three-dimensional space with spatially balanced proliferation and differentiation required for functional tissue development. The objective of this study was fabrication of nanofibrous matrix from novel biodegradable poly(p-dioxanone-co-L-lactide)-block-poly(ethylene glycol) (PPDO/PLLA-b-PEG) copolymer, and to examine cell proliferation, morphology of cell-matrix interaction with the electrospun nanofibrous matrix. The electrospun structure composed of PPDO/PLLA-b-PEG fibers with an average diameters of 380 nm, median pore size 8 microm, porosity more than 80% and mechanical strength 1.4 MPa, is favorable for cell-matrix interaction and supports the active biocompatibility of the structure. NIH 3T3 fibroblast cell seeded on the structure tend to maintain phenotypic shape and guided growth according to nanofiber orientation. Good capability of the nanofibrous structure for supporting the cell attachment and proliferation are observed. This novel biodegradable scaffold will be applicable for tissue engineering based upon its unique architecture, which acts to support and guide cell growth.

3T3 Cells↗

PubMed2005

In vitro characterization of chitosan-gelatin scaffolds for tissue engineering.

Recently, chitosan-gelatin scaffolds have gained much attention in various tissue engineering applications. However, the underlying cell-matrix interactions remain unclear in addition to the scaffold degradation and mechanical characteristics. In this study, we evaluated (i) the degradation kinetics of chitosan and chitosan-gelatin scaffolds in the presence of 10mg/L of lysozyme for dimensional stability, weight loss, and pH changes for a period of 2 months, (ii) tensile and compressive properties of films and scaffolds in wet state at 37 degrees C, (iii) viability of fibroblasts and human umbilical vein endothelial cells (HUVECs) on scaffolds, and (iv) the alteration in cell spreading characteristics, cytoskeletal actin distribution, focal adhesion kinase (FAK) distribution and PECAM-1 expression of HUVECs under static and 4.5, 8.5, 13 and 18 dyn/cm2 shear stress conditions. Degradation results showed that gelatin-containing chitosan scaffolds had faster degradation rate and significant loss of material than chitosan. Mechanical properties of chitosan are affected by the addition of gelatin although there was no clear trend. Three-dimensional chitosan and chitosan-gelatin scaffolds supported fibroblast viability equally. However, chitosan membranes decreased cell-spreading area, disrupted F-actin and localized FAK in the nucleus of HUVECs. Importantly, the lowest shear stress tested (4.5 dyn/cm2) for 3 h washed away cells on chitosan suggesting weak cell adhesion. In the blends, effect of gelatin was dominant; actin and FAK distribution were comparable to gelatin in static culture. However, at higher shear stresses, presence of chitosan inhibited shear-induced increase in cell spreading and weakened cell adhesive strength. No significant differences were observed in PECAM-1 expression. In summary, these results showed significant influence of blending gelatin with chitosan on scaffold properties and cellular behavior.

Actins↗

PubMed2004

Evaluation of mineralized collagen and alpha-tricalcium phosphate as scaffolds for tissue engineering of bone using human mesenchymal stem cells.

Owing to their plasticity and high proliferation capacity in vitro, mesenchymal stem cells (MSC) isolated from human bone marrow are promising candidates for use in tissue engineering approaches for the repair or replacement of mesenchymal tissues such as bone, cartilage or tendon. In keeping with the tissue engineering concept, these cells are cultivated on three-dimensional (3D) scaffolds to replace 3D tissue defects. Among the scaffolds tested for tissue engineering of bone, those containing phosphorus and calcium, as natural bone does, are the most promising candidates for this purpose. In this study, MSC from five patients were isolated from bone marrow. After in vitro expansion, cells were cultivated and differentiated towards the osteogenic lineage on mineralized collagen sponges and alpha-tricalcium phosphate (alpha-TCP). To analyze how appropriate these scaffolds would be for tissue engineering purposes, we established an in vitro characterization system to describe seeding efficiency, cell distribution and proliferation behavior on each scaffold. Real-time reverse transcriptase polymerase chain reaction quantification of important genes involved in osteogenic differentiation [e.g. bone sialoprotein (BSP), bone morphogenic protein 2, alkaline phosphatase and osteocalcin] was used to monitor the differentiation process of cells seeded on mineralized collagen and alpha-TCP. Using this in vitro characterization, we were able to demonstrate effective 3D growth of MSC on both scaffolds investigated. Improved osteogenic differentiation was observed on the scaffolds as compared to control monolayers. Of the two matrices, mineralized collagen was superior to alpha-TCP with regard to seeding efficacy (98 vs. 67%, p = 0.0003), increase in osteogenic marker genes (BSP expression on day 24, Pcollagen vs. TCP = 0.046) and 3D cell alignment (cell infiltration up to 500 vs. 200 microm). In conclusion, our data suggest that mineralized collagen is a promising candidate for use as a scaffold in tissue engineering of bone.

Adult↗

PubMed2002

Preparation and biocompatibility of tissue-engineered scaffold materials based on collagen.

OBJECTIVE: To prepare a tissue-engineered scaffold material using collagen as the matrices and to study the blood compatibility and tissue biocompatibility of this material. METHODS: Physical, chemical and physical/chemical methods were used for the crosslinking of the collagen. RESULTS: Dynamic blood clotting tests indicated that the blood clotting index (BCI) of the crosslinked collagen materials prepared by different means decreased as their contact with the blood was prolonged, and the collagen material obtained after crosslink through 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide method showed the highest BCI after contact with the blood within certain length of time. Hemolysis ratios of all the crosslinked collagen materials were shown to be much lower than 5%, well conforming to the requirement of biomaterials. Scanning electron microscopy showed that the platelets attached to the surface of the crosslinked collagen materials, having a fairly small number, were not morphologically distorted. CONCLUSION: The collagen materials obtained by the 3 crosslink methods have good blood compatibility. The cells grow well on the surfaces of the materials, indicating their good biocompatibility.

Biocompatible Materials↗

PubMed2004

Factors affecting the structure and properties of bioactive foam scaffolds for tissue engineering.

Resorbable 3D macroporous bioactive scaffolds have been produced for tissue-engineering applications by foaming sol-gel-derived bioactive glasses of the 58S (60 mol% SiO2, 36 mol% CaO, 4 mol% P2O5) composition with the aid of a surfactant. Bioactive glasses are known to have the ability to regenerate bone, and to release ionic biological stimuli that promote bone-cell proliferation by gene activation. The foams exhibit a hierarchical structure, with interconnected macropores (10-500 microm), which provide the potential for tissue ingrowth and mesopores (2-50 nm), which enhance bioactivity and release of ionic products. Many factors in the sol-gel and foaming processes can be used to control these pore sizes and distributions. This work concentrates on the effect of the processing temperature, gelling agent concentration, and the amount of water used for the foam generation on the structure, pore morphology, and the properties of the foam scaffold. The simplest and most reproducible method for controlling the modal pore diameter was by the amount of water added during the foaming process. The in vitro dissolution and bioactivity of the bioactive foams were compared to that of unfoamed monoliths and powders (< 20 microm in diameter) of the same composition.

Biocompatible Materials↗

PubMedDate not supplied

Effects of filtration seeding on cell density, spatial distribution, and proliferation in nonwoven fibrous matrices.

The cell seeding density and spatial distribution in a 3-D scaffold are critical to the morphogenetic development of an engineered tissue. A dynamic depth-filtration seeding method was developed to improve the initial cell seeding density and spatial distribution in 3-D nonwoven fibrous matrices commonly used as tissue scaffolds. In this work, trophoblast-like ED27 cells were seeded in poly(ethylene terephthalate) (PET) matrices with various porosities (0.85-0.93). The effects of the initial concentration of cells in the suspension used to seed the PET matrix and the pore size of the matrix on the resulting seeding density and subsequent cell proliferation and tissue development were studied. Compared to the conventional static seeding method, the dynamic depth-filtration seeding method gave a significantly higher initial seeding density (2-4 x 10(7) vs 4 x 10(6) cells/cm3), more uniform cell distribution, and a higher final cell density in the tissue scaffold. The more uniform initial cell spatial distribution from the filtration seeding method also led to more cells in S phase and a prolonged proliferation period. However, both uniform spatial cell distribution and the pore size of the matrices are important to cell proliferation and morphological development in the seeded tissue scaffold. Large-pore matrices led to the formation of cell aggregates and thus might reduce cell proliferation. The dynamic depth-filtration seeding method is better in providing a higher initial seeding density and more uniform cell distribution and is easier to apply to large tissue scaffolds. A depth-filtration model was also developed and can be used to simulate the seeding process and to predict the maximum initial seeding densities in matrices with different porosities.

Biocompatible Materials↗

PubMed2006

Electrospinning versus knitting: two scaffolds for tissue engineering of the aortic valve.

Two types of scaffolds were developed for tissue engineering of the aortic valve; an electrospun valvular scaffold and a knitted valvular scaffold. These scaffolds were compared in a physiologic flow system and in a tissue-engineering process. In fibrin gel enclosed human myofibroblasts were seeded onto both types of scaffolds and cultured for 23 days under continuous medium perfusion. Tissue formation was evaluated by confocal laser scanning microscopy, histology and DNA quantification. Collagen formation was quantified by a hydroxyproline assay. When subjected to physiologic flow, the spun scaffold tore within 6 h, whereas the knitted scaffold remained intact. Cells proliferated well on both types of scaffolds, although the cellular penetration into the spun scaffold was poor. Collagen production, normalized to DNA content, was not significantly different for the two types of scaffolds, but seeding efficiency was higher for the spun scaffold, because it acted as a cell impermeable filter. The knitted tissue constructs showed complete cellular in-growth into the pores. An optimal scaffold seems to be a combination of the strength of the knitted structure and the cell-filtering ability of the spun structure.

Aortic Valve↗

PubMed2005

Regulation of cellular infiltration into tissue engineering scaffolds composed of submicron diameter fibrils produced by electrospinning.

We characterize the infiltration of interstitial cells into tissue engineering scaffolds prepared with electrospun collagen, electrospun gelatin, electrospun poly(glycolic) acid (PGA), electrospun poly(lactic) acid (PLA), and an electrospun PGA/PLA co-polymer. Electrospinning conditions were optimized to produce non-woven tissue engineering scaffolds composed of individual fibrils less than 1000 nm in diameter. Each of these materials was then electrospun into a cylindrical construct with a 2 mm inside diameter with a wall thickness of 200-250 microm. Electrospun scaffolds of collagen were rapidly, and densely, infiltrated by interstitial and endothelial cells when implanted into the interstitial space of the rat vastus lateralis muscle. Functional blood vessels were evident within 7 days. In contrast, implants composed of electrospun gelatin or the bio-resorbable synthetic polymers were not infiltrated to any great extent and induced fibrosis. Our data suggests that topographical features, unique to the electrospun collagen fibril, promote cell migration and capillary formation.

Animals↗

PubMed2005

Stimulation of osteoblast responses to biomimetic nanocomposites of gelatin-hydroxyapatite for tissue engineering scaffolds.

Collagen-derived gelatin/hydroxyapatite (HA) nanocomposites were biomimetically synthesized for hard tissue engineering scaffold. In vitro osteoblastic cellular responses to the nanocomposites were assessed in comparison with those conventionally mixed gelatin-HA composites. A three-dimensional culture method involving floating cells in a culture medium was introduced to assist in the initial attachment of the cells to the scaffolds, and the proliferation and differentiation behaviors of the cells were examined. The osteoblastic MG63 cells attached to the nanocomposites to a significantly higher degree and subsequently proliferated more. The alkaline phosphatase (ALP) activity and osteocalcin produced by the cells were significantly higher on the nanocomposite scaffolds than on the conventional composite scaffolds. These improved cellular responses on the nanocomposites are considered to result from the increased ionic release and serum protein adsorption on the nanocomposites, which was derived from the different structural and morphological characteristics, i.e., the nanocomposite scaffolds retained less-crystallized and smaller-sized apatite crystals and a more well-developed pore configuration than the conventional ones. Based on these findings, the biomimetically synthesized nanocomposite scaffolds are believed to be potentially useful in hard tissue regeneration and tissue engineering fields.

Alkaline Phosphatase↗

PubMed2002

Three-dimensional seeding of chondrocytes encapsulated in collagen gel into PLLA scaffolds.

Tissue engineering approaches have been clinically tried to repair damaged articular cartilages. It is an essential step to uniformly seed chondrocytes into 3D scaffolds in order to reconstruct tissue-engineered cartilages in vitro, but the tissue engineering could not have been provided with efficient cell seeding methods. Type I collagen is clinically used and known as a cytocompatible material, having recognition sites for integrins. Collagen gel encapsulating chondrocytes has been tried for making regenerated cartilages, but it is found difficult to have the gel keep its original shape after long-term culture, because of shrinking. On the other hand, 3D scaffolds, either of a nonwoven structure or a sponge-like structure, involve difficulty in that chondrocytes could not be uniformly seeded, although they have adequate initial mechanical properties. In this study, by combining collagen gelation with a nonwoven PLLA scaffold, we achieved uniform cell seeding into the 3D scaffold. Bovine articular chondrocytes were mixed with type I collagen solution, and the solution was poured into the nonwoven PLLA scaffold (1.5 mm thick, diameter 15 mm). The collagen-chondrocyte mixture was made into gel at 37 degrees C for 1 h. The 0.39% collagen mixture was viscous enough to prevent cells from precipitating during gelation. Almost all chondrocytes were able to be incorporated into the PLLA scaffolds by mixing with collagen solution and subsequently making into gel, while 30-40% of the chondrocytes seeded as a cell suspension were not trapped into the PLLA scaffolds. The method presented, where chondrocytes were mixed with collagen solution, and the mixture was incorporated into a 3D scaffold, then made into gel in the scaffold, could serve as an alternative for in vitro cartilage regeneration, also simultaneously having the advantages of both materials.

Animals↗

PubMed2005

[Fabrication and properties of a composite chitosan/type II collagen scaffold for tissue engineering cartilage].

OBJECTIVE: To develop a novel porous three-dimensional scaffold and to investigate its physico-chemical properties for tissue engineering cartilage. METHODS: Refined 88% deacetylation degree chitosan was prepared and dissolved in 0.2 mol/L acetate acid and fully mixed with highly purified porcine type II collagen in 0.5 mol/L acetate acid solution in a ratio of 4 to 1 (wt/wt). Freeze-drying process was employed to fabricate the composite scaffold. The construct was cross-linked by use of 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). A mechanical tester was utilized to determine the tensile strength change before and after cross-linking. The microstructure was observed via scanning electron microscopy (SEM). The lysozyme degradation was performed to evaluate the degradability of the scaffold in vitro. RESULTS: A bulk scaffold with desired configuration was obtained. The mechanical test showed that the cross-linking treatment could enhance the mechanical strength of the scaffold. The SEM results revealed that the two constituents evenly distributed in the scaffold and that the matrix was porous, sponge-like with interconnected pore sizing 100-250 microm. In vitro lysozyme degradation indicated that cross-linked or uncross-linked composite scaffolds had faster degradation rate than the chitosan matrix. CONCLUSION: Chitosan and type II collagen can be developed into a porous three-dimensional scaffold. The related physico-chemical tests suggest that the composite scaffold meets requirements for tissue engineered scaffold and may serve as an alternative cell-carrier for tissue engineering cartilage.

Cartilage↗

PubMed2003

In vitro evaluation of novel bioactive composites based on Bioglass-filled polylactide foams for bone tissue engineering scaffolds.

Highly porous poly(DL-lactic acid) (PDLLA) foams and Bioglass-filled PDLLA composite foams were characterized and evaluated in vitro as bone tissue engineering scaffolds. The hypothesis was that the combination of PDLLA with Bioglass in a porous structure would result in a bioresorbable and bioactive composite, capable of supporting osteoblast adhesion, spreading and viability. Composite and unfilled foams were incubated in simulated body fluid (SBF) at 37 degrees C to study the in vitro degradation of the polymer and to detect hydroxyapatite (HA) formation, which is a measure of the materials' in vitro bioactivity. HA was detected on all the composite samples after incubation in SBF for just 3 days. After 28 days immersion the foams filled with 40 wt % Bioglass developed a continuous layer of HA. The formation of HA for the 5 wt % Bioglass-filled foams was localized to the Bioglass particles. Cell culture studies using a commercially available (ECACC) human osteosarcoma cell line (MG-63) were conducted to assess the biocompatibility of the foams and cell attachment to the porous substrates. The osteoblast cell infiltration study showed that the cells were able to migrate through the porous network and colonize the deeper regions within the foam, indicating that the composition of the foams and the pore structures are able to support osteoblast attachment, spreading, and viability. Rapid formation of HA on the composites and the attachment of MG-63 cells within the porous network of the composite foams confirms the high in vitro bioactivity and biocompatibility of these materials and their potential to be used as scaffolds in bone tissue engineering and repair.

Biocompatible Materials↗

PubMed2006

In vitro evaluation of potential calcium phosphate scaffolds for tissue engineering.

Nanocrystalline calcium phosphates are very interesting candidates as scaffolds for bone tissue engineering. These materials show excellent in vivo biocompatibility, cell proliferation, and resorption. In this work we have studied the osteoblast-like cell behavior seeded onto HA and BCP synthesized by controlled crystallization method and treated at different temperatures. In vitro cell attachment, proliferation, differentiation, spreading, and cytotoxicity tests have been carried out. The results can be explained as a function of the phase composition and microstructure. Under in vitro closed conditions, nanocrystalline HA depletes the calcium of the medium avoiding cell proliferation, whereas well-crystallized HA enhances high cell proliferation. On the other hand, nanocrystalline BCPs supply Ca(2+) to the medium due to the higher solubility of the beta-TCP component, allowing an excellent in vitro cellular response when osteoblast-like cells are seeded on it. These features make BCPs excellent candidates as scaffolds for bone tissue engineering.

Alkaline Phosphatase↗

PubMed2006

A structural model for the flexural mechanics of nonwoven tissue engineering scaffolds.

The development of methods to predict the strength and stiffness of biomaterials used in tissue engineering is critical for load-bearing applications in which the essential functional requirements are primarily mechanical. We previously quantified changes in the effective stiffness (E) of needled nonwoven polyglycolic acid (PGA) and poly-L-lactic acid (PLLA) scaffolds due to tissue formation and scaffold degradation under three-point bending. Toward predicting these changes, we present a structural model for E of a needled nonwoven scaffold in flexure. The model accounted for the number and orientation of fibers within a representative volume element of the scaffold demarcated by the needling process. The spring-like effective stiffness of the curved fibers was calculated using the sinusoidal fiber shapes. Structural and mechanical properties of PGA and PLLA fibers and PGA, PLLA, and 50:50 PGA/PLLA scaffolds were measured and compared with model predictions. To verify the general predictive capability, the predicted dependence of E on fiber diameter was compared with experimental measurements. Needled nonwoven scaffolds were found to exhibit distinct preferred (PD) and cross-preferred (XD) fiber directions, with an E ratio (PD/XD) of approximately 3:1. The good agreement between the predicted and experimental dependence of E on fiber diameter (R2 = 0.987) suggests that the structural model can be used to design scaffolds with E values more similar to native soft tissues. A comparison with previous results for cell-seeded scaffolds (Engelmayr, G. C., Jr., et al., 2005, Biomaterials, 26(2), pp. 175-187) suggests, for the first time, that the primary mechanical effect of collagen deposition is an increase in the number of fiber-fiber bond points yielding effectively stiffer scaffold fibers. This finding indicated that the effects of tissue deposition on needled nonwoven scaffold mechanics do not follow a rule-of-mixtures behavior. These important results underscore the need for structural approaches in modeling the effects of engineered tissue formation on nonwoven scaffolds, and their potential utility in scaffold design.

Biocompatible Materials↗

PubMed2003

Fabrication of precise cylindrical three-dimensional tissue engineering scaffolds for in vitro and in vivo bone engineering applications.

It is sometimes necessary to form highly porous polymeric tissue engineering scaffolds into various shapes and sizes. Ideally, in these cases, the three-dimensional morphology should be maintained to the outer margins of the scaffold so as to provide optimum function. Many biodegradable polymeric scaffolds are soft and delicate, however, and their poor physical strength presents a challenge when cutting these materials into the required shapes. We describe a simple device that can be used quickly and accurately to cut cylindrical shapes from such delicate polymeric scaffold materials, which maintain their morphological features to the margins of the shapes produced. We demonstrate that the device can be used to create scaffolds with reproducible dimensions having an SD in mass of less then 6%. The in vitro utility of scaffolds cut with the device was established through demonstrating bone marrow-derived cell invasion into fibrin-filled scaffolds that fit precisely into the wells of 24-well plates. We also demonstrate the in vivo utility of precise cylindrically shaped scaffolds by observing rapid bone invasion into 2.4-mm diameter scaffolds that have been placed into drill hole defects in the distal femur of young rats. When scaffolds are filled with fibrin before implantation as part of a bone tissue engineering strategy, less blood fills the defect site and the fibrin is gradually remodeled and replaced by bone. The ability to cut precise cylindrical scaffolds in the millimeter size range has allowed for the creation of a new small animal model that may prove useful for screening tissue engineering scaffolds for further study.

Animals↗

PubMed2005

Effects of porosity and pore size on in vitro degradation of three-dimensional porous poly(D,L-lactide-co-glycolide) scaffolds for tissue engineering.

In vitro degradation of seven three-dimensional porous scaffolds composed of PLGA85/15, a very useful poly(D,L-lactide-co-glycolide), was performed in phosphate-buffered saline solution at 37 degrees C up to 26 weeks, and effects of porosity (80-95%) and pore size (50-450 mum) on the degradation of the scaffolds were investigated. A series of quantities were measured during the degradation processes: molecular weight and its distribution of PLGA; compressive strength and modulus; and weight, dimension, and porosity of scaffolds. In all of cases with different pore morphologies, the degradation processes obeyed a three-stage model. Scaffolds with a higher porosity or a smaller pore size degraded more slowly than and thus outlasted those with a lower porosity or a larger pore size. The effects are both attributed to a wall effect and a surface area effect because the scaffolds with lower porosities or larger pores possess thicker pore walls and smaller surface area, which depress the diffusion of acidic degradation products and thus results in a stronger acid-catalyzed hydrolysis. This work suggests that, in designing a tissue-engineering scaffold composed of PLGA and adjusting its degradation rate, the effects of pore morphologies should be taken into consideration in addition to those of chemical composition and condensed state of raw materials.

Biocompatible Materials↗