Hydrogels: Properties and Applications in Biomedicine.

Hydrogels are crosslinked polymer chains with three-dimensional (3D) network structures, which can absorb relatively large amounts of fluid. Because of the high water content, soft structure, and porosity of hydrogels, they closely resemble living tissues. Research in recent years shows that hydrogels have been applied in various fields, such as agriculture, biomaterials, the food industry, drug delivery, tissue engineering, and regenerative medicine. Along with the underlying technology improvements of hydrogel development, hydrogels can be expected to be applied in more fields. Although not all hydrogels have good biodegradability and biocompatibility, such as synthetic hydrogels (polyvinyl alcohol, polyacrylamide, polyethylene glycol hydrogels, etc.), their biodegradability and biocompatibility can be adjusted by modification of their functional group or incorporation of natural polymers. Hence, scientists are still interested in the biomedical applications of hydrogels due to their creative adjustability for different uses. In this review, we first introduce the basic information of hydrogels, such as structure, classification, and synthesis. Then, we further describe the recent applications of hydrogels in 3D cell cultures, drug delivery, wound dressing, and tissue engineering.

Sol-gel based synthesis and biological properties of zinc integrated nano bioglass ceramics for bone tissue regeneration.

Bone is a flexible and electro active tissue that is vulnerable to various traumatic injuries. The self-healing of damaged bone tissue towards reconstruction is limited due to the lack of proper niche compliances. Nevertheless, the classical grafting techniques like autograft/allograft for bone repair pose challenges like bacterial infections and donor-site morbidity with unsatisfactory outcomes. The use of appropriate biomaterial with osteogenic potential can meet these challenges. In this regard, bioactive glass ceramics is widely used as a bone filler or graft material because of its bonding affinity to bone leading towards bone reconstruction applications without the challenge of post implant infections. Hence, the current study is aimed at addressing this potentiality of zinc (Zn) for doped the bioglass at nano-scale advantages for bone tissue repair. Since, Zn has been demonstrated to have not only antibacterial property but also the stimulatory effect on osteoblasts differentiation, mineralization by enhancing the osteogenic genes expression. In view of these, the present study is focused on sol-gel synthesis and pysico-chemical characterization of Zinc-doped bioglass nanoparticles (Zn-nBGC) and also analyzing its biological implications. The surface morphological and physiochemical characterizations using SEM, EDX, FT-IR and XRD analysis has shown the increased surface area of Zn-nBGC particles providing a great platform for biomolecular interaction, cytocompatibility, cell proliferation and osteogenic differentiation. The obtaining hydroxy apatite groups have initiated in vitro mineralization towards osteogenic lineage formation. Zn has not only involved in enhancing cellular actions but also strengthen the ceramic nanoparticles towards antibacterial application. Hence the finding suggests a biomaterial synthesis of better biomaterial for bone tissue engineering application by preventing post-operative bacterial infection.

Biocompatibility of Materials for Biomedical Engineering.

In the tissue engineering research field, nanobiomaterials highlight the impact of novel bioactive materials in both current applications and their potentials in future progress for tissue engineering and regenerative medicine. Tissue engineering is a well-investigated and challenging biomedical field, with promising perspectives to improve and support quality of life for the patient. To assess the response of those extracellular matrices (ECMs), induced by biomedical materials, this review will focus on cell response to natural biomaterials for biocompatibility.

Developing a Silk Fibroin Composite Film to Scavenge and Probe H2O2 Associated with UV-Excitable Blue Fluorescence.

A silk fibroin composite film that can simultaneously scavenge and probe H2O2 in situ was developed for possibly examining local concentrations of H2O2 for biomedical applications. A multi-functional composite film (GDES) that consists of graphene oxide (G), a photothermally responsive element that was blended with polydopamine (PDA, D)/horseradish peroxidase (HRP, E) (or DE complex), and then GDE microaggregates were coated with silk fibroin (SF, S), a tyrosine-containing protein. At 37 °C, the H2O2-scavenging ability of a GDES film in solution at approximately 7.5 × 10-3 µmol H2O2/mg film was the highest compared with those of S and GS films. The intensities of UV-excitable blue fluorescence of a GDES film linearly increased with increasing H2O2 concentrations from 4.0 µM to 80 µM at 37 °C. Interestingly, after a GDES film scavenged H2O2, the UV-excitable blue fluorescent film could be qualitatively monitored by eye, making the film an eye-probe H2O2 sensor. A GDES film enabled to heat H2O2-containing samples to 37 °C or higher by the absorption of near-IR irradiation at 808 nm. The good biocompatibility of a GDES film was examined according to the requirements of ISO-10993-5. Accordingly, a GDES film was developed herein to scavenge and eye-probe H2O2 in situ and so it has potential for biomedical applications.

Activation of the ubiquitin proteasome pathway by silk fibroin modified chitosan nanoparticles in hepatic cancer cells.

Silk fibroin (SF) is a protein with bulky hydrophobic domains and can be easily purified as sericin-free silk-based biomaterial. Silk fibroin modified chitosan nanoparticle (SF-CSNP), a biocompatible material, has been widely used as a potential drug delivery system. Our current investigation studied the bio-effects of the SF-CSNP uptake by liver cells. In this experiment, the characterizations of SF-CSNPs were measured by particle size analysis and protein assay. The average size of the SF-CSNP was 311.9 ± 10.7 nm, and the average zeta potential was +13.33 ± 0.3 mV. The SF coating on the SF-CSNP was 6.27 ± 0.17 µg/mL. Moreover, using proteomic approaches, several proteins involved in the ubiquitin proteasome pathway were identified by analysis of differential protein expressions of HepG2 cell uptake the SF-CSNP. Our experimental results have demonstrated that the SF-CSNP may be involved in liver cancer cell survival and proliferation.

Dopamine-dependent functions of hyaluronic acid/dopamine/silk fibroin hydrogels that highly enhance N-acetyl-L-cysteine (NAC) delivered from nasal cavity to brain tissue through a near-infrared photothermal effect on the NAC-loaded hydrogels.

Hyaluronic acid/silk fibroin (HA/SF or HS) hydrogels with remarkable mechanical characteristics have been reported as tissue engineering biomaterials. Herein, the addition of dopamine/polydopamine (DA/PDA) to HS hydrogels to develop multifunctional HA/PDA/SF (or HDS) hydrogels for the delivery of drugs such as N-acetyl-L-cysteine (NAC) from nasal to brain tissue is examined. Herein, DA-dependent functions of HDS hydrogels with highly adhesive forces, photothermal response (PTR) effects generated by near infrared (NIR) irradiation, and anti-oxidative effects were demonstrated. An in-vitro study shows that the HDS/NAC hydrogels could open tight junctions in the RPMI 2650 cell line, a model cell of the nasal mucosa, as demonstrated by the decreased values of transepithelial electrical resistance (TEER) and more discrete ZO-1 staining than those for the control group. This effect was markedly enhanced by NIR irradiation of the HDS/NAC-NIR hydrogels. Compared to the results obtained using NAC solution, an in-vivo imaging study (IVIS) in rats showed an approximately nine-fold increase in the quantity of NAC delivered from the nasal cavity to the brain tissue in the span of 2 h through the PTR effect generated by the NIR irradiation of the nasal tissue and administration of the HDS/NAC hydrogels. Herein, dopamine-dependent multifunctional HDS hydrogels were studied, and the nasal administration of HDS/NAC-NIR hydrogels with PTR effects generated by NIR irradiation was found to have significantly enhanced NAC delivery to brain tissues.

Assessing the responses of cellular proteins induced by hyaluronic acid-modified surfaces utilizing a mass spectrometry-based profiling system: over-expression of CD36, CD44, CDK9, and PP2A.

The cell responses to biopolymer surface at the early adhesion stages can be critical for cell survival. The purpose of this research was to assess formation of hyaluronic acid (HA) biopolymer surface, the fibroblasts were used as an experimental model to evaluate the responses of cellular proteins induced by biopolymer materials using a mass spectrometry-based profiling system. Surfaces were covered by multi-walled carbon nanotubes (CNT), chitosan (CS), and HA to increase the surface area, enhance the adhesion of biopolymer and promote the rate of cell proliferation. The amount of adhered fibroblasts on CNT/CS/HA electrodes of quartz crystal microbalance (QCM) were greatly exceeded those on other surfaces that were consistent with cell-count technique. Moreover, analyzing differential protein expressions of adhered fibroblasts on those biopolymer surfaces by proteomic approaches identified CD36, CD44, PP2A, and CDK9 as key proteins. To validate the influences of those four proteins on adhesions of fibroblasts on biopolymers, the cells were blocked by antibodies of the proteins and the adhesions of cells on the tested biopolymer surfaces were examined using a QCM technique, flow cytometric analysis and morphological observations. The results of significantly decreasing the weights and densities of the blocked fibroblasts adhering to CNT/CS/HA surfaces were obtained, and validate those proteins found by proteomic approaches. Utilizing mass spectrometry-based proteomics to evaluate cell adhesions on biopolymers is proposed.

Determining early adhesion of cells on polysaccharides/PCL surfaces by a quartz crystal microbalance.

The early adhesions of cells to various biopolymers are important to their growths and proliferations. Here, the adhesion of cells (e.g., fibroblasts) on the electrode of a quartz crystal microbalance (QCM) that was coated by PCL or PEG/PCL and further adsorbed by chitosan (CS) or CS/hyaluronic acid (HA) layers, was examined by cell-counting technique, QCM method and MTS assay under a serum-free condition for 3 h. The surfaces on electrodes of the QCM were confirmed to have been modified by measuring their contact angles, FT-IR spectra and the weights of biopolymers affected the frequency shifts of the QCM. Among tested surfaces on electrodes, the adhesion of fibroblasts on a HA/CS/PCL surface was the most (e.g., 3.08 × 10(5) cells/cm(2)) while that on a PEG/PCL surface was the least (e.g., 0.7 × 10(5) cells/cm(2)), as determined by cell-counting technique. The frequency shift and the mass of adhering fibroblasts on HA/CS/PCL electrodes were -3,537 ± 770 Hz and 3.78 ± 0.22 µg (n = 3), respectively, that were significantly exceeded those on other electrodes (-393 ± 58 Hz and 0.32 ± 0.06 µg, n = 3, respectively, for PEG/PCL electrodes). These results were consistent with cell-counting technique. Although MTS assay yielded similar results, it was less sensitive than the two aforementioned methods. In conclusion, modified electrodes of a QCM provide a convenient and sensitive method for examining the early adhesion of cells (e.g., 3 h) to biopolymer surfaces.

Antioxidative NAC-Loaded Silk Nanoparticles with Opening Mucosal Tight Junctions for Nasal Drug Delivery: An In Vitro and In Vivo Study.

Using nasal routes to deliver drugs to the brain using multifunctional nanoparticles (NPs) to bypass the blood-brain barrier (BBB) might enhance the delivery efficacy. Anti-oxidative N-Acetyl-L-cysteine (NAC)-loaded silk fibroin (SF/NAC) NPs are produced, characterized and studied as a potential delivery vehicle for NAC delivered to the brain via nasal for both in vitro and in vivo studies. The NPs are not cytotoxic to RPMI 2650 cells, mucosal model cells, at a concentration of 6000 µg/mL. The anti-oxidative activities of SF/NAC NPs are demonstrated by high H2O2 scavenge capacities of the NPs and shown by mitochondrial superoxide (MitoSOX) immunostaining of human mesenchymal stem cells. Tight junctions in RPMI 2650 cells are opened after 30 min of incubation with SF/NAC NPs, which are demonstrated by measuring the decrease in trans-epithelial electrical resistance (TEER) values and discreteness in ZO-1 stains. The cellular uptake of SF/NAC NPs by RPMI 2650 cells is significantly greater than that for SF NPs and increased with increasing incubation time. In an in vivo imaging study (IVIS) using rats shows that the amount of NAC that is delivered to the brain by SF/NAC NPs increased by 1.40-2.60 times and NAC is retained longer in the nasal cavity than NAC solutions in a 2-h study.

Biomaterial-induced conversion of quiescent cardiomyocytes into pacemaker cells in rats.

Pacemaker cells can be differentiated from stem cells or transdifferentiated from quiescent mature cardiac cells via genetic manipulation. Here we show that the exposure of rat quiescent ventricular cardiomyocytes to a silk-fibroin hydrogel activates the direct conversion of the quiescent cardiomyocytes to pacemaker cardiomyocytes by inducing the ectopic expression of the vascular endothelial cell-adhesion glycoprotein cadherin. The silk-fibroin-induced pacemaker cells exhibited functional and morphological features of genuine sinoatrial-node cardiomyocytes in vitro, and pacemaker cells generated via the injection of silk fibroin in the left ventricles of rats functioned as a surrogate in situ sinoatrial node. Biomaterials with suitable surface structure, mechanics and biochemistry could facilitate the scalable production of biological pacemakers for human use.

Characterization of ADAM28 as a biomarker of bladder transitional cell carcinomas by urinary proteome analysis.

Human urine contains a large number of proteins and peptides (the urinary proteome). Global analysis of the human urinary proteome is important for understanding urinary tract diseases. Bladder cancer is the most common urological cancer with higher incidence rates in endemic areas of Blackfoot disease (BFD) in southern Taiwan. The aim of this study was to use the proteomic approach to establish urinary protein biomarkers of bladder cancer. ADAM28, identified by proteomic approaches and confirmed by Western blotting, showed significant differences compared with normal individuals, so it may be a biomarker of bladder cancer.

Evaluation of transdifferentiation from mesenchymal stem cells to neuron-like cells using microfluidic patterned co-culture system.

We design a microfluidic patterned co-culture system for mouse mesenchymal stem cells (mMSCs) and neural cells to demonstrate the paracrine effects produced by the neural cells in facilitating the transdifferentiation from mMSCs to neuron-like cells. Neural cells and mMSC are orderly patterned in the microfluidic co-culturing system without direct cell contact. This configuration provides us to calculate the percentage of neural marker transdifferentiated by mMSCs easily. We obtain higher transdifferentiated ratio of mMSC in the microfluidic co-culturing system (beta III tubulin: 67%; glial fibrillary acidic protein (GFAP): 86.2%) as compared with the traditional transwell co-culturing system (beta III tubulin: 59.8%; GFAP: 52.0%), which is similar to the spontaneous neural marker expression in the undifferentiated MSCs (beta III tubulin: 47.5%; GFAP: 60.1%). Furthermore, mMSCs expressing green fluorescent protein and neural cells expressing red fluorescent protein were also used in our co-culture system to demonstrate the rarely occurring or observed cell fusion phenomenon. The results show that the co-cultured neural cells increased the transdifferentiation efficiency of mMSCs from soluble factors secreted by neural cells.

Protein profiling of human nonpigmented ciliary epithelium cell secretome: the differentiation factors characterization for retinal ganglion cell line.

The purpose of this paper was to characterize proteins secreted from the human nonpigmented ciliary epithelial (HNPE) cells, which have differentiated a rat retinal ganglion cell line, RGC-5. Undifferentiated RGC-5 cells have been shown to express several marker proteins characteristic of retinal ganglion cells. However, RGC-5 cells do not respond to N-methyl-D aspartate (NMDA), or glutamate. HNPE cells have been shown to secrete numbers of neuropeptides or neuroproteins also found in the aqueous humor, many of which have the ability to influence the activity of neuronal cells. This paper details the profile of HNPE cell-secreted proteins by proteomic approaches. The experimental results revealed the identification of 132 unique proteins from the HNPE cell-conditioned SF-medium. The biological functions of a portion of these identified proteins are involved in cell differentiation. We hypothesized that a differentiation system of HNPE cell-conditioned SF-medium with RGC-5 cells can induce a differentiated phenotype in RGC-5 cells, with functional characteristics that more closely resemble primary cultures of rat retinal ganglion cells. These proteins may replace harsh chemicals, which are currently used to induce cell differentiation.

Urinary protein profiling by liquid chromatography/tandem mass spectrometry: ADAM28 is overexpressed in bladder transitional cell carcinoma.

Bladder cancer is the most common urological cancer with higher incidence rate in the endemic areas of Blackfoot disease (BFD) in southern Taiwan. The aim of this study was to utilize the proteomic approach to establish urinary protein patterns of bladder cancer. The experimental results showed that most patients with bladder cancer had proteinuria or albuminuria. The urine arsenic concentrations of bladder cancer patients in BFD areas were significantly higher than those patients from non-BFD areas. In the proteomic analysis, the urinary proteome was identified by nano-high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (nano-HPLC/ESI-MS/MS) followed by peptide fragmentation pattern analysis. We categorized 2782 unique proteins of which 89 proteins were identified with at least three unique matching peptide sequences. Among these 89 proteins, thirteen of them were not found in the control group and may represent proteins specific for bladder cancer. In this study, three proteins, SPINK5, ADAM28 and PTP1, were also confirmed by Western blotting and showed significant differential expression compared with the control group. ADAM28 may be used as a possible biomarker of bladder cancer.

Characterization of surface modification on self-assembled monolayer-based piezoelectric crystal immunosensor for the quantification of serum α-fetoprotein.

Self-assembled monolayers (SAMs) on coinage metallic material can provide versatile modeling systems for studies of interfacial electron transfer, biological interactions, molecular recognition and other interfacial phenomena. Recently, a bio-sensing system has been produced by analysis of the attachment of antibody using alkanethiols, to form SAMs on the face of Au-quartz crystal microbalance (QCM) surfaces. In this study, the attachment of anti-α-fetoprotein monoclonal antibody to a SAMs surface of 11-mercaptoundecanoic acid was achieved using water-soluble N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide as coupling agents. Surface analyses were utilized by X-ray photoelectron spectroscopy and atomic force microscopy. The quantization of immobilized antibody was characterized by the frequency shift of QCM and the radioactivity change of ¹²5I labeled antibody. The limit of detection and linear range of the calibration curve of the QCM method were 15 ng/ml and 15-850 ng/ml. The correlation coefficients of α-fetoprotein concentration between QCM and radioimmunoassay were 0.9903 and 0.9750 for the standards and serum samples, respectively. This report illustrates an investigation of SAMs for the preparation of covalently immobilized antibody biosensors.

Metal doped calcium silicate biomaterial for skin tissue regeneration in vitro.

This study spots light on combined Wound healing process conjoining blood coagulation, inflammation reduction, proliferation and remodeling of the cells. The objective is to overcome the drawbacks of conventional clinically applied wound dressings such as poor rigidity, porosity, mechanical potency and bactericidal activity. As nosocomial infection is a very common condition at the wound site, bio-adhesive materials with intrinsic antibacterial properties are used in clinical applications. Considering the provenability of Wollastonite [Calcium silicate (CaSiO3)] to regenerate the soft tissues by inducing vascularization and regeneration of fibroblast cells And the antibacterial potentiality of zinc in clinical applications, the present study focuses on synthesis of Zn-Ws particles and evaluation of its antimicrobial and wound healing potentialities towards skin tissue engineering applications. The compositional characterization by EDAS and FT-IR spectral analysis have substantiated the presence of major elements and corresponding band stretching associated with the synthesized particles whereas the particles morphology by SEM images have shown the size of the Ws and Zn-Ws to be 370 nm and 530 nm respectively. From the in vitro studies, skin regenerative potential of Zn-Ws was determined on promoting fibroblast cell (NIH3T3) proliferation by providing better adhesiveness, biocompatibility and cytocompatibility. The antibacterial property of Zn-Ws evaluation by minimum inhibitory concentration (MIC) and zone of inhibition (ZOI) methods against clinical isolates of Gram +Ve and Gram -Ve bacterial strains have confirmed that the addition of Zn has diminished the bacterial growth and also helped in degrading the bacterial biofilms. Thus it is summed up that the process of wound healing is expected to occur with reduced risk of post-injury infections by the presence of zinc-doping on wollastonite for skin tissue application.

Developing photothermal-responsive and anti-oxidative silk/dopamine nanoparticles decorated with drugs which were incorporated into silk films as a depot-based drug delivery.

Photothermal-responsive (PTR) and anti-oxidative silk fibroin/dopamine nanoparticles (SD NPs) mediated by tyrosinase were produced, and decorated either by curcumin or albumin (BSA) to produce SD/curcumin or SD/BSA NPs as drug delivery vehicles, respectively. Both drug loaded NPs were further blended into SF solutions to produce SD films, as a depot-based drug delivery. The reaction mechanisms for producing new SD NPs were proposed. Anti-oxidative activities for SD NPs were examined by H2O2 scavenge capacities of NPs. NPs were not cytotoxic at concentration of 1000µg/mL. Moreover, heparin was coated to SD films to produce SDH films for temporary implants. Cumulative release profiles for drugs loaded SDH films showed fast releases and then sustained releases stages. Furthermore, the releases of curcumin in sustained stages for varying SD/curcumin NPs loaded into SDH films were dependent on amounts of NPs. BSA releases profiles for SD/BSA NPs loaded into SDH films were similar to those profiles for the films carried with SD/curcumin NPs but release periods of BSA were short. Degrees of PTR effects with irradiation of near infrared on the releases of two drugs loaded films were different. Blood clot at wound areas of rats with SDH films implantations was not found for 24 h study.

Silk fibroin/chitosan-hyaluronic acid versus silk fibroin scaffolds for tissue engineering: promoting cell proliferations in vitro.

The feasibility of silk fibroin protein (SF) scaffolds for tissue engineering applications to promote cell proliferation has been demonstrated, as well as the ability to mimic natural extra-cellular matrix (ECM), SF/chitosan (CS), a polysaccharide, scaffolds for tissue engineering. However, the response of cells to SF/CS-hyaluronic acid (SF/CS-HA) scaffolds has not been examined, which this study attempts to do and then compares those results with those of SF scaffolds. SF/CS-HA microparticles were fabricated to produce scaffolds in order to examine the proliferations of human dermal fibroblasts (HDF) in the scaffolds. Positive zeta potentials and ATR-FTIR spectra confirmed the co-existence of SF and CS-HA in SF/CS-HA microparticles. HDF proliferated well and migrated into SF/CS-HA scaffolds for around 160 mum in depth, as well as those in SF scaffolds after 7 days of cultivation, as observed using confocal microscopy. Interestingly, HDF grown in SF/CS-HA scaffolds had a markedly higher cell density than that in SF ones. Additionally, MTT assay revealed that the growth rates of HDF in SF/CS-HA scaffolds significantly exceeded (P < 0.01, n = 5) those in scaffolds of SF and SF/CS. The daily glucose consumptions and lactate formations, metabolic parameters, of HDF grown in SF/CS-HA and SF/CS scaffolds were significantly higher (P < 0.01, n = 3) than those in SF ones in most culturing days. Results of this study suggest that SF/CS-HA scaffolds have better cell responses for tissue engineering applications than SF ones.

PCP copolymers grafted with RGD enhance the rates of RGD-PCP micelles internalized into cells.

RGD-PCP copolymers were fabricated by grafting Arg-Gly-Asp (RGD) peptide to poly(epsilon-caprolactone)-b-chitooligosaccharide-b-poly(ethylene glycol) (PCP) copolymers and the rate of internalization of RGD-PCP micelles by PC 12 cells were examined. Increasing intensity of the absorbance of amine groups in FT-IR spectra of RGD-PCP copolymers compared with those of PCP copolymers indicated the presence of RGD in new copolymers. Moreover, the grafting efficiency and molar ratio of RGD peptides to PCP copolymers were 88.2% and 0.45, respectively, analysed with HPLC. The RGD-PCP copolymers self-assemble to micelles at the critical micelle concentration (CMC) of 0.018 wt% (178 mg L(-1)) and with a mean diameter of 90 nm using a dynamic light-scattering (DLS) analyser. Interestingly, the internalization of DPH-loaded RGD-PCP micelles into PC 12 cells is much faster (e.g. within 5 min) than that of PCP micelles. The new RGD-PCP micelles may potentially be used in cellular drug delivery.

Roles of Silk Fibroin on Characteristics of Hyaluronic Acid/Silk Fibroin Hydrogels for Tissue Engineering of Nucleus Pulposus.

Silk fibroin (SF) and hyaluronic acid (HA) were crosslinked by horseradish peroxidase (HRP)/H2O2, and 1,4-Butanediol di-glycidyl ether (BDDE), respectively, to produce HA/SF-IPN (interpenetration network) (HS-IPN) hydrogels. HS-IPN hydrogels consisted of a SF strain with a high content of tyrosine (e.g., strain A) increased viscoelastic modules compared with those with low contents (e.g., strain B and C). Increasing the quantities of SF in HS-IPN hydrogels (e.g., HS7-IPN hydrogels with weight ratio of HA/SF, 5:7) increased viscoelastic modules of the hydrogels. In addition, the mean pores size of scaffolds of the model hydrogels were around 38.96 ± 5.05 µm which was between those of scaffolds H and S hydrogels. Since the viscoelastic modulus of the HS7-IPN hydrogel were similar to those of human nucleus pulposus (NP), it was chosen as the model hydrogel for examining the differentiation of human bone marrow-derived mesenchymal stem cell (hBMSC) to NP. The differentiation of hBMSC induced by transforming growth factor ß3 (TGF-ß3) in the model hydrogels to NP cells for 7 d significantly enhanced the expressions of glycosaminoglycan (GAG) and collagen type II, and gene expressions of aggrecan and collagen type II while decreased collagen type I compared with those in cultural wells. In summary, the model hydrogels consisted of SF of strain A, and high concentrations of SF showed the highest viscoelastic modulus than those of others produced in this study, and the model hydrogels promoted the differentiation of hBMSC to NP cells.