Long-Term Fluorescent Tissue Marking Using Tissue-Adhesive Porphyrin with Polycations Consisting of Quaternary Ammonium Salt Groups.

Localization of tumors during laparoscopic surgery is generally performed by locally injecting India ink into the submucosal layer of the gastrointestinal tract using endoscopy. However, the location of the tumor is obscured because of the black-stained surgical field and the blurring caused by India ink. To solve this problem, in this study, we developed a tissue-adhesive porphyrin with polycations consisting of quaternary ammonium salt groups. To evaluate the ability of tissue-adhesive porphyrin in vivo, low-molecular-weight hematoporphyrin and tissue-adhesive porphyrin were injected into the anterior wall of the exposed stomach in rats. Local injection of low-molecular-weight hematoporphyrin into the anterior wall of the stomach was not visible even after 1 day because of its rapid diffusion. In contrast, the red fluorescence of the tissue-adhesive porphyrin was visible even after 7 days due to the electrostatic interactions between the positively-charged moieties of the polycation in the tissue-adhesive porphyrin and the negatively-charged molecules in the tissue. In addition, intraperitoneal injection of tissue-adhesive porphyrin in rats did not cause adverse effects such as weight loss, hepatic or renal dysfunction, or organ adhesion in the abdominal cavity. These results indicate that tissue-adhesive porphyrin is a promising fluorescent tissue-marking agent.

TLR3 polymorphisms are associated with the severity of hand, foot, and mouth disease caused by enterovirus A71 in a Chinese children population.

Hand, foot, and mouth disease (HFMD) caused by enterovirus A71 (EV-A71) is a contagious viral disease, and toll-like receptors (TLRs) play essential roles in resisting the pathogen. The aim of this study was to assess the potential relationship between several TLRs polymorphisms and the HFMD severity in a Chinese children population. A total of 328 Chinese children with HFMD were included in the present study. The polymorphisms of TLR3 (rs3775290, rs3775291, rs3775296, rs1879026, rs5743312, rs5743313, rs5743303, rs13126816, and rs3775292), TLR4 (rs4986790, rs4986791, rs2149356, rs11536889, and rs41426344), TLR7 (rs179009, rs179010, rs179016, rs3853839, rs2302267, rs1634323, and rs5741880), and TLR8 (rs3764880, rs2159377, rs2407992, rs5744080, rs3747414, rs3764879, and rs5744069) genes were selected. The study indicated that individuals with the GG genotype of TLR3 single-nucleotide polymorphism rs1879026 had a higher risk of developing severe cases (GG vs. GT: OR = 1.875; 95% CI, 1.183-2.971; p = .007). Meanwhile, TLR3 rs3775290 CC genotype and C allele were associated with lower disease severity in females (CC vs. CT: OR = 0.350; 95% CI, 0.163-0.751; p = .006; C vs. T: OR = 0.566; 95% CI, 0.332-0.965; p = .036). TLR3 rs3775291 CC genotype showed 2.537 folds higher risk of developing severe cases in females (CC vs. CT: OR = 2.537; 95% CI, 1.108-5.806; p = .026). Moreover, TLR3 rs1879026 GG genotype was found to be related to increased risk of severe cases in males (GG vs. GT: OR = 2.076; 95% CI, 1.144-3.768; p = .016). The current findings show that the genetic variants of TLR3 rs1879026, rs3775290, and rs3775291 are associated with the severity of EV-A71-associated HFMD in a Chinese children population.

Evaluation of skeletal muscle perfusion in canine hind limb ischemia model using color-coded digital subtraction angiography.

OBJECTIVE: To evaluate perfusion alterations in skeletal muscle in a canine hind limb ischemia model using color-coded digital subtraction angiography (CC-DSA). METHODS: Twelve beagles underwent embolization at the branch of their left deep femoral artery. Right hind limbs were used as the control group. Angiography was performed before and immediately after embolization. Upon CC-DSA analysis, time to peak (TTP) was measured before embolization in both sides of the beagles' hind limbs at the middle iliac artery, and the distant, middle and proximal femoral artery. Regions of interest (ROI) peak and ROI peak time were symmetrically computed in proximal and distal thigh muscles before and immediately after embolization. The data were analyzed and compared using the Wilcoxon signed rank test. RESULTS: Before embolization, ROI peak in the proximal thigh was lower than in the ipsilateral distal thigh, whereas ROI peak time in the proximal thigh was longer than in the distal thigh. In the iliac femoral artery, there was no significant difference in ROI peak, ROI peak time, or TTP between right and left sides. After embolization, ROI peaks in proximal and distal skeletal muscles of the left hind limb were significantly lower than on the contralateral side. ROI peak time was significantly longer in the left proximal and left distal thigh compared to the contralateral side. There were no significant changes in ROI peak or ROI peak time in the right proximal and right distal thigh compared to pre-embolization values. Changes in ROI peak and ROI peak time were larger in the left proximal than in the left distal thigh. CONCLUSION: CC-DSA provided real-time measurement of changes in vascular hemodynamics and skeletal muscle perfusion without increasing X-ray usage or contrast agent dose.

Smart composite scaffold to synchronize magnetic hyperthermia and chemotherapy for efficient breast cancer therapy.

Combination of different therapies is an attractive approach for cancer therapy. However, it is a challenge to synchronize different therapies for maximization of therapeutic effects. In this work, a smart composite scaffold that could synchronize magnetic hyperthermia and chemotherapy was prepared by hybridization of magnetic Fe3O4 nanoparticles and doxorubicin (Dox)-loaded thermosensitive liposomes with biodegradable polymers. Irradiation of alternating magnetic field (AMF) could not only increase the scaffold temperature for magnetic hyperthermia but also trigger the release of Dox for chemotherapy. The two functions of magnetic hyperthermia and chemotherapy were synchronized by switching AMF on and off. The synergistic anticancer effects of the composite scaffold were confirmed by in vitro cell culture and in vivo animal experiments. The composite scaffold could efficiently eliminate breast cancer cells under AMF irradiation. Moreover, the scaffold could support proliferation and adipogenic differentiation of mesenchymal stem cells for adipose tissue reconstruction after anticancer treatment. In vivo regeneration experiments showed that the composite scaffolds could effectively maintain their structural integrity and facilitate the infiltration and proliferation of normal cells within the scaffolds. The composite scaffold possesses multi-functions and is attractive as a novel platform for efficient breast cancer therapy.

Doxorubicin-encapsulated thermosensitive liposome-functionalized photothermal composite scaffolds for synergistic photothermal therapy and chemotherapy.

Synergistic therapy, especially the combination of photothermal therapy and chemotherapy, has been proposed as an effective therapeutic approach for breast cancer treatment. In this study, a smart platform for synergistic photothermal therapy and chemotherapy was developed by hybridizing doxorubicin-encapsulated thermosensitive liposomes and gold nanorods into porous scaffolds of gelatin and polyglutamic acid (Dox-lipo/AuNR/Gel/PGA). The Dox-lipo/AuNR/Gel/PGA composite scaffolds had good photothermal conversion and temperature-dependent doxorubicin release properties. Under near-infrared laser irradiation, the composite scaffolds increased the local temperature to not only kill the breast cancer cells in the scaffolds but also accelerate the release of doxorubicin to eliminate the breast cancer cells surrounding the scaffolds. In vitro cell culture and in vivo mouse experiments demonstrated that the synergistic effects of photothermal ablation combined with doxorubicin-induced inhibition of the breast cancer cells in and surrounding the composite scaffolds under near-infrared laser irradiation. Moreover, after drug release was complete, the composite scaffolds fostered human bone marrow-derived mesenchymal stem cell proliferation. These results suggested that the composite scaffolds provided synergistic photothermal therapy and chemotherapy for breast cancer cell elimination at the early stage and promoted stem cell activities at the late stage. Therefore, this composite scaffold holds great potential as a synergistic therapy platform for breast cancer treatment.

Sustainable and efficient reduction of pollutants by immobilized PEG-P/Ag/Ag2O/Ag3PO4/TiO2 photocatalyst for purification of saline wastewater.

In this study, we have reported an efficient and stable degradation of pollutants at salinity condition using newly developed solar-light-driven silicone-TiO2 based photocatalytic immobilized system. The interfacial layer of Silicone-PEG-P/Ag/Ag2O/Ag3PO4/TiO2 (S-PEG/PAgT) photocatalyst exhibited higher surface roughness, hydrophobicity, better light absorption, and narrow band gap than S-TiO2. The Rh B degradation by S-PEG/PAgT (91.2%) was 1.71 folds higher than S-TiO2 (53.5%) under simulated solar light irradiation. The reduction rate was significantly higher in S-PEG/PAgT (0.0792 min-1) than S-TiO2 (0.0229 min-1). The S-PEG/PAgT demonstrated high TOC removal (>80%), high repeatability (10 cycles) and excellent activity after 30 days of incubation in aqueous NaCl. The mechanism analysis revealed the synergistic effect of surface morphology with irregular chamfered edges and photoinduced reactive species (O2-) with successive formation of free chlorine radicals (Cl) contributed to the removal of pollutants in saline wastewater. Therefore, considering the above advantages of high efficiency and effective elimination of organics illustrates the potential of newly developed S-PEG/PAgT immobilized system in long-term practical treatment real seawater and ballast water.

PLGA-collagen-BPNS Bifunctional composite mesh for photothermal therapy of melanoma and skin tissue engineering.

The treatment of melanoma requires not only the elimination of skin cancer cells but also skin regeneration to heal defects. To achieve this goal, a bifunctional composite scaffold of poly(DL-lactic-co-glycolic acid) (PLGA), collagen and black phosphorus nanosheets (BPNSs) was prepared by hybridizing a BPNS-embedded collagen sponge with a PLGA knitted mesh. The composite mesh increased the temperature under near-infrared laser irradiation. The incorporation of BPNSs provided the PLGA-collagen-BPNS composite mesh with excellent photothermal properties for the photothermal ablation of melanoma cells both in vitro and in vivo. The PLGA-collagen-BPNS composite mesh had high mechanical strength for easy handling. The PLGA-collagen-BPNS composite mesh facilitated the proliferation of fibroblasts, promoted the expression of angiogenesis-related genes and the genes of components of the extracellular matrix for skin tissue regeneration. The high mechanical strength, photothermal ablation capability and skin tissue regeneration effects demonstrate that the bifunctional PLGA-collagen-BPNS composite mesh is a versatile and effective platform for the treatment of melanoma and the regeneration of skin defects.

Adipogenic differentiation of individual mesenchymal stem cell on different geometric micropatterns.

Micropatterned surfaces are very useful to control cell microenvironment and investigate the physical effects on cell function. In this study, poly(vinyl alcohol) (PVA) micropatterns on polystyrene cell-culture plates were prepared using UV photolithography. Cell adhesive polystyrene geometries of triangle, square, pentagon, hexagon, and circle were surrounded by cell nonadhesive PVA to manipulate cell shapes. These different geometries had the same small surface areas for cell spreading. Human mesenchymal stem cells (MSCs) were cultured on the micropatterned surface, and the effect of cell geometry on adipogenic differentiation was investigated. MSCs adhered to the geometric micropatterns and formed arrays of single cell with different shapes. The distribution patterns of actin filaments were similar among these cell shapes and remolded during adipogenesis. The adipogenic differentiation potential of MSCs was similar on the small size triangular, square, pentagonal, hexagonal, and circular geometries according to lipid vacuoles staining. This simple micropatterning technique using photoreactive molecules will be useful for creating micropatterns of arbitrary design on an organic surface, and cell functions can be directly and systematically compared on a single surface without external factors resulting from separate cell culture and coating method.

[Diagnosis and treatment of 12 patients with deep neck infection and inferior mediastinal infection].

Objective:To summarize the clinical manifestations and treatment of patients with deep neck infection with descending mediastinal infection. Methods:The clinical data of 12 patients with deep neck infection with descending mediastinal infection were reviewed. The clinical manifestations, infection origin, bacterial culture results, related systemic diseases, surgical drainage methods and treatment results were analyzed. Results:The typical clinical features of descending mediastinal infection were chest pain and subcutaneous crackling, diagnosis can confirmed by CT scan detected gas and abscess in the neck and mediastinal space. The main origin of infection was pharyngeal infection, followed by odontogenic infection. Systemic diseases were mainly diabetes mellitus. The positive rate of purulent secretion culture was 58.3%（7/12）, streptococcus account for the highest proportion. Surgical treatment included 9 patients undergoing neck surgery alone and 3 patients undergoing combined neck and chest surgery. Chest drainage was performed by thoracic surgery through mediastinoscopy or thoracoscopic surgery or B-ultrasound guided puncture, and no patient underwent open surgery. Ten patients were cured and two died, with a mortality rate of 16.7%. Conclusion:The deep neck infection with descending mediastinal infection has no specificity in the early stage. Timely abscess drainage, effective airway protection, antimicrobial therapy, and management of potentially life-threatening complications such as sepsis, mediastinitis, and pneumonia are the key to successful treatment.

Interconnected collagen porous scaffolds prepared with sacrificial PLGA sponge templates for cartilage tissue engineering.

Interconnected pore structures of scaffolds are important to control the cell functions for cartilage tissue engineering. In this study, collagen scaffolds with interconnected pore structures were prepared using poly(D,L-lactide-co-glycolide) (PLGA) sponges as sacrificial templates. Six types of PLGA sponges of different pore sizes and porosities were prepared by the solvent casting/particulate leaching method and used to regulate the interconnectivity of the collagen scaffolds. The integral and continuous templating structure of PLGA sponges generated well-interconnected pore structures in the collagen scaffolds. Bovine articular chondrocytes cultured in collagen scaffolds showed homogenous distribution, fast proliferation, high expression of cartilaginous genes and high secretion of cartilaginous extracellular matrix. In particular, the collagen scaffold templated by the PLGA sacrificial sponge that was prepared with a high weight ratio of PLGA and large salt particulates showed the most promotive effect on cartilage tissue formation. The interconnected pore structure facilitated cell distribution, cell-cell interaction and cartilage tissue regeneration.

Black Phosphorus Nanosheets Induced Oxidative Stress In Vitro and Targeted Photo-thermal Antitumor Therapy.

Black phosphorus (BP) nanosheets with excellent features have been broadly employed for cancer therapy. BPs in blood were known to form BP nanomaterial-corona complexes, yet not explored their biological effects. In this study, BPs as delivery vehicles loaded with doxorubicin (DOX) (BP-DOX) by electrostatic interaction had been successfully prepared for photo-thermal/chemotherapy with a tumor inhibition rate of 81.47% more than the rates of BPs (69.50%) and free DOX (51.91%) in the Hela-bearing mice model by a pH/photo-responsive controlled drug release property. Then, in vivo experiments demonstrated that the treatment of healthy mice with BPs led to mild inflammation in the body and oxidative stress in the liver and lung which caused cell apoptosis. In vitro studies further showed that oxidative stress and metabolic disorders could be induced by BPs in A549, HepG2, Beas-2B, and LO2 cells. Lastly, the RGD peptide-conjugated red blood cell (RBC) membrane-coated BPs (RGD-RBC@BP) was prepared by lipid insertion and co-ultrasound methods for efficient photo-thermal therapy (PTT) cancer via a tumor-targeted strategy. RGD-RBC@BP showed positive biocompatibility, photo-thermal properties, and increased cellular uptake by Hela cells benefited by the long circulation property of RBC and RGD peptides. Pharmacokinetics and bio-distribution study of RGD-RBC@BP were found to prolong circulation time and tended to accumulate in the tumors, which overexpression of ανß3 integrin rather than livers after intravenous injection 24 h in vivo. After 808 nm laser irradiation, RGD-RBC@BP nanoparticles exhibited a better PTT than PEGylated BPs (BP-PEG). The active-targeting strategy of biomimetic nanomaterials based on the tumor microenvironment have been proved to have favorable biological prospects in cancer PTT.

Tracheal defect repair using a PLGA-collagen hybrid scaffold reinforced by a copolymer stent with bFGF-impregnated gelatin hydrogel.

PURPOSE: We studied the regenerated cartilage in tracheal defect repair and compared the bio-materials used versus native trachea using basic fibroblast growth factor (bFGF)-impregnated gelatin hydrogel. MATERIALS AND METHODS: A full-thickness anterior defect was created in the cervical trachea of 15 experimental rabbits. The defect was implanted with a hybrid scaffold of poly(lactic-co-glycolic acid) (PLGA) knitted mesh and collagen sponge. The implanted trachea was reinforced with a copolymer stent of polycaprolactone and poly(lactic acid) coarse fiber mesh. A gelatin hydrogel was used for providing a sustained release of bFGF. The reconstructed tracheas were divided into three groups with wrapped materials; without gelatin hydrogel (control group, n = 5), a gelatin hydrogel with saline (gelatin group, n = 5), and a gelatin hydrogel with 100 microg of bFGF (bFGF group, n = 5). One of the five rabbits in each group at 1 month after operation, one at 3 months, and three at 6 months were killed and the engineered tracheas were evaluated histologically. Biomechanical properties were evaluated on samples at 6 months postoperatively. RESULTS: The rigid support in the defect portion was maintained during 6 months postoperatively. The newly regenerated cartilages were recognized between the host cartilage stumps at 3 months postoperatively in the bFGF group, and limited new cartilage growth and epithelialization were observed at 6 months postoperatively. CONCLUSIONS: The experiment shows that using bFGF, better mechanical strength was obtained but with poor cartilage growth.

PLGA-collagen-ECM hybrid meshes mimicking stepwise osteogenesis and their influence on the osteogenic differentiation of hMSCs.

Extracellular matrices (ECMs) are dynamically altered and remodeled during tissue development. How the dynamic remodeling of ECM affects stem cell functions remains poorly understood due to the difficulty of obtaining biomimetic ECMs. In this study, stepwise osteogenesis-mimicking ECM-deposited hybrid meshes were prepared by culturing human mesenchymal stem cells (hMSCs) in poly (lactic-co-glycolic acid) (PLGA)-collagen hybrid meshes and controlling the stages of the osteogenesis of hMSCs. Three types of hybrid mesh mimicking the ECMs that were secreted from stem cell stage of hMSCs (SC-ECM), early stage (EO-ECM) and late stage (LO-ECM) osteogenesis of hMSCs were prepared. The stepwise osteogenesis-mimicking ECM deposited PLGA-collagen hybrid meshes showed different ECM compositions associated with the stage of osteogenesis. Their effects on the osteogenic differentiation of hMSCs differed. EO-ECM scaffold increased and LO-ECM scaffold moderately promoted the osteogenic differentiation of hMSCs. However, SC-ECM scaffold inhibited the osteogenic differentiation of hMSCs. The novel PLGA-collagen-ECM hybrid meshes will provide useful tools for stem cell culture and tissue engineering.

Adipogenic differentiation of mesenchymal stem cells on micropatterned polyelectrolyte surfaces.

Three kinds of photoreactive polyelectrolytes of polyallylamine (PAAm), poly(acrylic acid) (PAAc), and poly(vinyl alcohol) (PVA) were synthesized by the introduction of azidophenyl groups in the respective polymers. The photoreactive PAAm, PAAc, and PVA were micropatterned on polystyrene surfaces by photolithography. Observation with optical microscopy and scanning probe microscopy demonstrated the formation of a striped pattern of polyelectrolytes with a width of 200 microm. The micropatterned polyelectrolytes swelled in water. The micropatterned surfaces were used for cell culture of mesenchymal stem cells (MSCs) and their effects on adipogenic differentiation were investigated. The MSCs adhered to and proliferated evenly on the PAAm- and PAAc-patterned surfaces while they formed a cell pattern on the PVA-patterned surface. The PAAm-, PAAc-grafted, and polystyrene surfaces supported cell adhesion while the PVA-grafted surface did not. When cultured in adipogenic differentiation medium, the adipogenic differentiation of MSCs on the polyelectrolyte-patterned surfaces was demonstrated by the formation of lipid vacuoles and gene expression analysis. Oil Red-O-positive cells showed an even distribution on the PAAm- and PAAc-patterned surfaces, while they showed a pattern on the PVA-patterned surface. The fraction of Oil RedO-positive cells increased with culture time. The MSCs cultured on the PAAm-, PAAc-grafted, and polystyrene surfaces in adipogenic differentiation medium expressed the adipogenesis marker genes of peroxisome proliferator-activated receptor gamma2 (PPARgamma2), lipoprotein lipase (LPL), and fatty acid binding protein 4 (FABP4). These results indicate that the PAAm-, and PAAc-grafted, and polystyrene surfaces supported the adipogenesis of MSCs while a PVA-grafted surface did not.

PLGA-collagen-ECM hybrid scaffolds functionalized with biomimetic extracellular matrices secreted by mesenchymal stem cells during stepwise osteogenesis-co-adipogenesis.

A shift in osteogenesis toward adipogenesis of human bone marrow-derived mesenchymal stem cells (hMSCs) is a crucial pathological factor in the progression of osteoporosis. The development of an in vitro three-dimensional (3D) model that reflects the dynamic remodeling of extracellular matrices (ECMs) during simultaneous osteogenesis and adipogenesis of hMSCs can provide a useful tool to mimic the process and to investigate how 3D ECMs balance the osteogenic and adipogenic differentiation of hMSCs. In this study, ECMs secreted by hMSCs during their stepwise osteogenesis-co-adipogenesis were deposited on hybrid meshes of poly(lactide-co-glycolide) (PLGA) and collagen to prepare biomimetic PLGA-collagen-ECM hybrid scaffolds. Four types of stepwise differentiation ECMs were prepared: ECMs secreted by hMSCs at early stages of osteogenesis and adipogenesis (EOEA-ECMs), hMSCs at early stages of osteogenesis and late stages of adipogenesis (EOLA-ECMs), hMSCs at late stages of osteogenesis and early stages of adipogenesis (LOEA-ECMs) and hMSCs at late stages of osteogenesis and late stages of adipogenesis (LOLA-ECMs). The deposited ECMs had different compositions that were dependent on the different stages of osteogenesis and adipogenesis. They also showed different effects on balancing the adipogenic and osteogenic differentiation of hMSCs. The EOEA-ECM scaffold had a promotive effect on adipogenesis and a suppressive effect on the osteogenesis of hMSCs. The LOEA-ECM and LOLA-ECM scaffolds showed a promotive effect on osteogenesis and a moderate effect on the adipogenic differentiation of hMSCs. The EOLA-ECM scaffold exhibited a suppressive effect on both osteogenesis and adipogenesis of hMSCs. However, the EOLA-ECM scaffold promoted hMSC proliferation more strongly than the other ECM scaffolds. The results indicated that dynamically remodeling ECM scaffolds could affect the osteogenic and adipogenic differentiation of hMSCs and should provide a useful 3D cell culture model for the investigation of ECM-cell interactions.

Encapsulation of individual living cells with enzyme responsive polymer nanoshell.

Cell delivery in cell therapy is typically challenged by the low cell survival rate and immunological rejection during cells injection and circulation. Encapsulation of cells with semipermeable hydrogels or membranes can improve cell viability by resisting high shear force and inhibit immune response with the physical isolation effect. Herein, the individual HeLa cells and human mesenchymal stem cells (hMSCs) were encapsulated with enzyme responsive polymer nanoshell. The encapsulation shell was prepared via the Layer-by-Layer (LbL) assembly of functionalized gelatin and click chemistry of peptide linker and gelatin. The encapsulated cells showed high cell viability and could resist the physical stress. Moreover, the encapsulation shell had a prolonged encapsulation sustaining period and could effectively prevent the invasion of external entities. In addition, on-site cell release was realized via enzymolysis of the encapsulation shell by human matrix metalloproteinase-7 (MMP-7), an overexpressed enzyme on tumor area. The finding of this study proved a potential approach in cell therapy, especially for cell-based cancer therapy.

Influence of Cell Spreading Area on the Osteogenic Commitment and Phenotype Maintenance of Mesenchymal Stem Cells.

Osteogenic differentiation and commitment of mesenchymal stem cells (MSCs) is a complex process that is induced and regulated by various biological factors and biophysical cues. Although cell spreading area, as a biophysical cue, has been demonstrated to play a critical role in the regulation of osteogenic differentiation of MSCs, it is unclear how it affects the maintenance of the committed phenotype after osteogenic differentiation of MSCs. In this study, poly (vinyl alcohol) was micropatterned on a tissue culture polystyrene surface, and the micropatterns were used to culture MSCs to control their cell spreading area. The influence of cell spreading area on osteogenic differentiation and maintenance of the differentiated phenotype of MSCs was investigated. MSCs with a larger spreading area showed a higher degree of osteogenic differentiation, slower loss of differentiated phenotype and slower re-expression of stem cell markers compared with MSCs with a smaller spreading area. A large cell spreading area was beneficial for osteogenic differentiation of MSCs and maintenance of their differentiated phenotype.

In vitro evaluation of biodegradation of poly(lactic-co-glycolic acid) sponges.

Evaluation of the degradability of porous scaffolds is very important for tissue engineering. A protocol in which the condition is close to the in vivo pH environment was established for in vitro evaluation of biodegradable porous scaffolds. Degradation of PLGA sponges in phosphate-buffered solution (PBS) was evaluated with the protocol. The PLGA sponges degraded with incubation time. For the first 12 weeks, the weight loss increased gradually and then remarkably after 12 weeks. In contrast, the number-average molecular weight (Mn) decreased dramatically for the first 12 weeks and then less markedly after 12 weeks. Thermal analysis showed that the glass transition temperatures (Tg) decreased rapidly for the first 12 weeks, and the change became less evident after 12 weeks. These results suggest that the degradation mechanism of PLGA sponges was dominated by autocatalyzed bulk degradation for the first 12 weeks and then by surface degradation after 12 weeks. Physical aging was observed during incubation at 37 degrees C. The heterogeneous structure caused by physical aging might be one of the driving forces that induced autocatalyzed bulk degradation. The degradation mechanism was further supported by the data of pH change and the morphology of the degraded PLGA sponges. The autocatalyzed acidic products flooded out after 8 weeks, the pH dropped, and the walls of the sponges became more porous. The increase of the pore surface area facilitated surface degradation after 12 weeks. The pH was in the range between 7.43 and 7.24 during the entire incubation time. The protocol suppressed extreme changes of the pH and will be useful in the biodegradation evaluation of porous scaffolds for tissue engineering.

Chondrogenic differentiation of human mesenchymal stem cells on photoreactive polymer-modified surfaces.

Human mesenchymal stem cells (MSCs) were cultured on polystyrene surfaces modified with photoreactive azidophenyl-derivatives of three different chargeable polymers, poly(acrylic acid) (PAAc), polyallylamine (PAAm), and poly(ethylene glycol) (PEG). The MSCs adhered and spread both on a PAAm-modified surface and on PAAc-modified and polystyrene (control) surfaces. However, the cells adhered more easily to the PAAm-modified surface. The MSCs did not attach to the PEG-modified surface and aggregated to form pellets immediately after cell seeding. The cells proliferated on the PAAc-, PAAm-modified and control surfaces with culture time, formed a monolayer, and aggregated to form pellets. The cells in the pellets that formed on the PAAm- and PEG-modified surfaces after 2 weeks culture had a round morphology and the extracellular matrices were positively stained by safranin O and toluidine blue, while those that formed on the PAAc-modified and control surfaces had a spindle, fibroblast-like morphology and were not positively stained by safranin O and toluidine blue. The pellets that formed on the PAAm- and PEG-modified surfaces contained significantly higher levels of sulfated glycosaminoglycans than did those that formed on the PAAc-modified and control surfaces. Type II collagen and cartilage proteoglycan were immunohistologically detected in the pellets that formed on PAAm- and PEG-modified surfaces, but not those that formed on the PAAc-modified and control surfaces. The MSCs cultured on the PAAm- and PEG-modified surfaces expressed a high level of cartilaginous genes encoding type II collagen and aggrecan, while the MSCs cultured on the PAAc-modified and control surfaces did not express these genes. These results suggest that the PAAm-modified surface supported cell adhesion and proliferation and also promoted chondrogenic differentiation of the MSCs. The PAAc-modified and polystyrene surfaces supported cell adhesion and proliferation, but not chondrogenic differentiation. The PEG-modified surfaces did not support cell adhesion, but did promote chondrogenic differentiation. The adhesion, proliferation, and differentiation of the MSCs could be controlled by surface chemistry.

[Development of novel biomaterials for bone and cartilage tissue engineering].

Three-dimensional porous scaffolds play an important role in cartilage and bone tissue engineering as temporary templates for transplanted cells to control their adhesion and proliferation to guide the formation of the new tissues. The scaffolds should be biodegradable, biocompatible, mechanically strong, and capable of being formed into desired shapes. Biodegradable synthetic polymers and naturally derived collagen have their respective advantages and drawbacks. Hybridization of the two kinds of polymers has been carried out to combine their respective advantages. This review will summarize some of the recently developed porous scaffolds having hybrid, biphasic and leakproof structures, and their application to bone and cartilage tissue engineering.