Silk Protein Sericin Research Articles

One-step synthesis of natural silk sericin-based microcapsules with bionic structures.

Different techniques are being developed for fabricating microcapsules; it is still a challenge to fabricate them in an efficient and environment-friendly process. Here, a one-step green route to synthesize silk protein sericin-based microcapsules without any assistance of organic solvents is reported. By carefully changing the concentration of calcium ions accompanied with stirring, the morphology of the microcapsules can easily be regulated to form either discoidal, biconcave, cocoon-like, or tubular structures. The chelation of Ca(2+) and shearing force from agitation may induce the conformational transformation of sericin, which possibly results in the formation of microcapsules through the self-assembly of the protein subsequently. The as-prepared cocoon-like microcapsules exhibit pH-dependent stability. A potential application of microcapsules being fabricated from natural water-soluble silk protein sericin for controlled bioactive molecules loading and release system by a pH-triggered manner is quite feasible.

PH responsive poly amino-acid hydrogels formed via silk sericin templating

Poly(amino acid) hydrogels have attracted a great deal of attention as biodegradable biomaterials that can limit products of synthetic polymer degradation. Here we report on a stimuli-responsive, porous, composite biomaterial based on the protein templating of the poly(amino acid) hydrogel from poly(aspartic acid) with the silk protein sericin. This low-cost, biocompatible and biodegradable hydrogel demonstrates a greatly increased porosity and improvement in volumetric swelling over networks formed from pure poly(aspartic acid). The swelling capacity measured over a range of pH values surrounding physiological pH 7.0 demonstrates a linear profile, in which hydrogel volume and mass increase to a maximum, with an increase as a function of higher sericin content. In comparison to pure poly(aspartic acid), this demonstrates a nearly 3-fold increase in retention volume at basic pH. The increase in swelling is also demonstrated by the increase in porosity and internal micro-architecture of the hydrogel networks. The biomaterial is then shown to perform well as a scaffold for cells with high mechanical strength and integrity. This protein- and homo poly(amino acid)-based super-swelling hydrogel has applications in drug delivery and tissue engineering as an economical and environmentally friendly biomaterial, in addition to ensuring the species incorporated maintain their biocompatibility during processing.

Development of Bread Supplemented with the Silk Protein Sericin

The present study aimed to develop sericin-added bread in an effort to promote the effective consumption of the silk protein sericin and to evaluate bread-baking performance with sericin addition, with respect to effects on bread structure and palatability. Sericin supplementation resulted in decreased specific volume and darker crust color of the bread. No significant difference was observed in other physical properties. Sensory evaluation revealed that bread with up to 2 g of added sericin tended to be preferred. In a comprehensive evaluation of specific volume, crust color and preference rating by sensory evaluation, the optimal amount of added sericin was determined to be 2 g. Further, approximately 330 mg of sericin can be consumed in 1 slice of bread. We thus propose sericin-added bread as a desirable processed food that enables the effective ingestion of sericin.

Fabrication of silk sericin/alginate microparticles by electrohydrodynamic spraying technique for the controlled release of silk sericin

Abstract Silk sericin has been recently investigated for many biological roles. This study aimed to develop the new delivery system to control the release of silk sericin. The alginate microparticles encapsulating silk sericin were fabricated by electrospraying technique. Concentrations of silk sericin and alginate polyelectrolyte solutions were investigated. All microparticles had an average size of 264–284 μm and could entrap silk sericin with high entrapment efficiency (84–89%). The microparticles could deliver silk sericin in a rate-controlled manner. This study would show a promising controlled release application of silk sericin protein from alginate microparticles fabricated by the means of electrostatic forces.

Formation of vaterite regulated by silk sericin and its transformation towards hydroxyapatite microsphere

The influence of soluble silk sericin (SS) protein on the formation of CaCO3 particles was investigated and the CaCO3 particles were then used as a template to synthesize the hydroxyapatite microspheres. The SS showed a strong preference to the mineralization of vaterite and the fine controls over the shape, size and uniformity of vaterite were carried out by the variation of pH value and reaction time in the presence of SS. Using the vaterites as a template, the homogeneous and monodispersed hydroxyapatite microspheres, copying faithfully the shape and size of original vaterites, were fabricated under the assistance of microwave irradiation. The research may provide a feasible method for the fabrication of hydroxyapatite-based biomaterials with controllable configuration.

Cryopreservation for bovine embryos in serum-free freezing medium containing silk protein sericin

Because the use of serum in the embryo cryopreservation increases the probability of animal health problems such as bovine spongiform encephalopathy (BSE) and viral infections, this study was conducted to examine the effects of sericin supplementation for serum-free freezing medium on the survival and development of bovine embryos after freezing–thawing and direct transfer to recipients. When in vitro-produced bovine embryos were frozen conventionally in the freezing medium supplemented with various concentrations (0.1%, 0.5%, and 1.0%) of sericin, the percentages of damaged zona pellucida, survival, and development of frozen–thawed embryos were similar to those of embryos frozen in freezing medium supplemented with 0.4% bovine serum albumin (BSA) and 20% fetal bovine serum (FBS) (0.4BSA/20F; control). When in vivo-derived embryos were frozen with 0.4BSA/20F (control), 0.5% sericin +20% FBS (0.5S/20F) or 0.5% sericin (0.5S) and were subsequently transferred directly to recipients, the percentages of recipients with pregnancy and normal calving in the 0.5S/20F group were higher than those in the control group (47.3% vs. 40.1% and 94.6% vs. 87.3%, respectively). Moreover, the percentages of recipients with pregnancy and normal calving (42.2% and 92.4%, respectively) in the 0.5S group were similar with those of other groups. In conclusion, these results indicate that serum-free freezing medium supplemented with sericin is available for the cryopreservation of bovine embryos and that it is beneficial for the elimination of a potential source of biological contamination by serum or BSA.

The promotion of osseointegration of titanium surfaces by coating with silk protein sericin

A promising strategy to influence the osseointegration process around orthopaedic titanium implants is the immobilization of bioactive molecules. This recruits appropriate interaction between the surface and the tissue by directing cells adhesion, proliferation, differentiation and active matrix remodelling. In this study, we aimed to investigate the functionalization of metallic implant titanium with silk protein sericin. Titanium surface was immobilized with non-mulberry Antheraea mylitta sericin using glutaraldehyde as crosslinker. To analyse combinatorial effects the sericin immobilized titanium was further conjugated with integrin binding peptide sequence Arg-Gly-Asp (RGD) using ethyl (dimethylaminopropyl) carbodiimide and N-hydroxysulfosuccinimide as coupling agents. The surface of sericin immobilized titanium was characterized biophysically. Osteoblast-like cells were cultured on sericin and sericin/RGD functionalized titanium and found to be more viable than those on pristine titanium. The enhanced adhesion, proliferation, and differentiation of osteoblast cells were observed. RT-PCR analysis showed that mRNA expressions of bone sialoprotein, osteocalcin and alkaline phosphatase were upregulated in osteoblast cells cultured on sericin and sericin/RGD immobilized titanium substrates. Additionally, no significant amount of pro-inflammatory cytokines TNF-α, IL-1β and nitric oxide production were recorded when macrophages cells and osteoblast-macrophages co culture cells were grown on sericin immobilized titanium. The findings demonstrate that the sericin immobilized titanium surfaces are potentially useful bioactive coated materials for titanium-based medical implants.

Effect of sericin on preimplantation development of bovine embryos cultured individually

The silk protein sericin has been identified as a potent antioxidant in mammalian cells. This study was conducted to examine the effects of sericin on preimplantation development and quality of bovine embryos cultured individually. When two-cell-stage embryos were cultured individually for 7 days in CR1aa medium supplemented with 0, 0.1, 0.5, or 1% sericin, rates of total blastocyst formation and development to expanded blastocysts from embryos cultured with 0.5% sericin were higher (P < 0.05) than those from embryos cultured with 0 or 1% sericin. When embryos were cultured individually for 7 days in the CR1aa medium supplemented with 0 or 0.5% sericin under two oxidative stress conditions (50 or 100 μm H2O2), the addition of sericin significantly improved the blastocyst formation rate of embryos exposed to 100 μm H2O2. However, the protective effect of sericin was not observed in development of embryos exposed to 50 μm H2O2. When embryos were exposed to 100 μm H2O2 during culture, the DNA fragmentation index of total blastocysts from embryos cultured with 0.5% sericin was lower than blastocysts derived from embryos cultured without sericin (4.4 vs. 6.8%; P < 0.01). In conclusion, the addition of 0.5% sericin to in vitro culture medium improved preimplantation development and quality of bovine embryos cultured individually by preventing oxidative stress.

Extraction and application of natural silk protein sericin from Bombyx mori as antimicrobial finish for cotton fabrics

In this study, we developed an effective technology for the extraction of sericin from the cocoons of Bombyx mori silk worms. Sericin was extracted with ice cold ethanol to obtain crude extract. Sericin extract was coated onto cotton fabric by a pad–dry–cure method. FTIR characterization of the sericin-coated cotton fabric showed distinct amide peaks. The test organisms that were used in the study to assess the antimicrobial activity of sericin were Escherichia coli and Staphylococcus aureus according to AATCC standard. The antimicrobial activity of the sericin thus extracted was assessed by both qualitative (agar diffusion and parallel streak method) and quantitative (percentage reduction test) methods. An inhibition zone of 28 mm and 30 mm for E. coli and S. aureus by agar diffusion method and a zone of 40 mm and 42 mm for E. coli and S. aureus by parallel streak method were obtained. Quantitative assessment by percentage reduction test showed a reduction percentage of 89.4% and 81% for S. aureus and E. coli, respectively. Results suggested that sericin might be a valuable ingredient for the development of antimicrobial textiles.

Potential of 2D crosslinked sericin membranes with improved biostability for skin tissue engineering

Silk sericin protein is a natural, hydrophilic, macromolecular glycoprotein mainly synthesized in the middle silk gland of the silkworm. It constitutes 25-30% of the silk cocoon. Sericin proteins have antioxidant, antimicrobial, UV-resistant properties, promote wound healing and support cell proliferation even in serum-free media. Most of the sericin is discarded as waste in silk processing industries. This study aims at improving the mechanical strength and stability of sericin extracted from the silk cocoons during processing and utilize it as a biocompatible natural biopolymer in biomedical applications. Crosslinked sericin membranes, from the cocoon of non-mulberry tropical silkworm, Antheraea mylitta, were prepared using gluteraldehyde as the crosslinking agent. Physical and structural characteristics of the membranes were analyzed using scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy and X-ray diffraction along with swelling and degradation studies. The secondary structure of the membrane indicates that crosslinking provides a more integrated structure that significantly improves the stability and mechanical strength of the membranes. In vitro cytocompatibility of the membranes was evaluated by MTT assay and cell cycle analysis of feline fibroblast cells. The adherence, growth and proliferation patterns of cells on membranes were assessed by confocal microscopy, which demonstrated that the latter is non-toxic and supports cell growth. Cell cycle analyses indicate cytocompatibility with normal cell cycle pattern. This study reveals that silk sericin protein can be used as a biocompatible natural biopolymer for various applications in the biomedical field.

Effect of the silk protein sericin on cryopreserved rat islets

Cryopreservation is necessary for the long-term storage of islet cells and to increase the practicality of clinical islet transplantation. Fetal bovine serum (FBS) supplemented with 10% dimethyl sulfoxide (DMSO) is generally used as a freezing medium for islet cells. However, FBS should ideally be avoided in cell culture and transplantation because of recent animal health problems, such as bovine spongiform encephalopathy and viral infections. The aim of this study was to develop a new serum-free freezing medium by examining the effectiveness of the silk protein sericin, which is produced by Bombyx mori. Islets prepared from Lewis rats by collagenase digestion and Histopaque gradient centrifugation, followed by culture in medium containing 0.1% sericin for 3 days, were cryopreserved using 0.1, 0.5, 1, 2, and 5% sericin or FBS. DMSO (1, 4, 7, 10, and 15%) was added to the medium as a cryoprotectant. After thawing, on days 1, 4, 7, and 14, viable islets were counted in order to evaluate their survival. Insulin secretion was measured in vitro by a static incubation test on day 4. The in vivo function of cultured islets was tested by syngeneic transplantation. Islets were evaluated histologically and immunohistochemically after transplantation. There were no significant differences between freezing medium containing 1% sericin and that containing 10% FBS with regard to the survival rate of islets and stimulated insulin secretion. Following transplantation, islets rapidly reversed hyperglycemia and maintained normal glycemic control. In addition, the use of 7% DMSO as a cryoprotectant with sericin showed the same results as higher DMSO concentrations with FBS. The present results showed that serum-free medium containing sericin is useful for both cryopreservation and cell culture.

Non-mulberry silk sericin/poly (vinyl alcohol) hydrogel matrices for potential biotechnological applications

This study reports a novel biopolymeric matrix fabricated by chemically cross-linking poly (vinyl alcohol) with silk sericin protein obtained from cocoons of the tropical tasar silkworm Antheraea mylitta. Glutaraldehyde was used as a cross-linking agent with hydrochloric acid acting as an initiator. The matrices were biophysically characterized and the cytocompatibility of the matrices was evaluated for their suitability as biomaterials. The surface morphology was assessed using atomic force microscopy while the changes taking place after cross-linking were confirmed by Fourier transform infrared spectroscopy. The enhanced thermal stability of the constructs was assessed by thermogravimetric and differential scanning calorimetry. Fourier transform infrared spectroscopy analysis showed that sericin was chemically cross-linked with poly (vinyl alcohol) using glutaraldehyde. Silk sericin protein demonstrated a favorable effect on animal cell culture by successfully improving the adhering and spreading of cells on the poorly adhering surface of poly (vinyl alcohol). Confocal microscopy revealed cell spreading and actin filament development in sericin/poly (vinyl alcohol) hydrogel matrices. These findings prove the potential of non-mulberry silk sericin/poly (vinyl alcohol) hydrogel matrices to be used as biocompatible and biopolymeric material for tissue-engineering and biotechnological applications.

213 THE EFFECTS OF SERICIN SUPPLEMENTATION IN IN VITRO CULTURE MEDIUM ON THE DEVELOPMENT AND CRYOSURVIVAL OF BOVINE IN VITRO-MATURED - IN VITRO-FERTILIZED EMBRYOS

The objective of this study was to investigate the feasibility of the silk protein sericin as an alternative protein supplement for bovine embryo cultures. The effects of sericin supplementation in in vitro culture (IVC) medium on the development and cryosurvival of bovine IVM-IVF embryos were investigated. Cumulus–oocyte complexes were collected from 2- to 8-mm follicles of ovaries obtained from a local abattoir. They were matured for 20 to 22 h in TCM-199 supplemented with 5% fetal bovine serum (FBS), 0.002 AU mL–1 of FSH, and 1 μg mL–1 of oestradiol-17β at 38.5°C under an atmosphere of 5% CO2 in air. After IVF (Day 0), presumptive zygotes were cultured in SOF medium (IVC medium) containing amino acids and supplemented with either 5% FBS (FBS group: n = 400) or sericin at 3 different concentrations (wt/vol; 0.05%: n = 493; 0.1%: n = 419; or 0.15%: n = 520; sericin groups) at 38.5°C under an atmosphere of 5% CO2, 5% O2, and 90% N2 for 5 days. They were then transferred into each IVC medium supplemented with 0.1 mM β-mercaptoethanol and cultured for an additional 4 days (9 days in total). Cleavage rates were recorded on Day 2 of IVC. The excellent expanded blastocysts harvested on Days 7 and 8 were used for freezing (FBS group: n = 51, 0.05% sericin group: n = 56, 0.1% sericin group: n = 44, 0.15% sericin group: n = 44). They were frozen in m-PBS supplemented with 1.5 M ethylene glycol, 0.1 M sucrose, 20% calf serum, and 4 mg mL–1 of BSA. After thawing, they were cultured in TCM-199 supplemented with 20% FBS and 0.1 mM β-mercaptoethanol under the same atmosphere used for IVC for 72 h. Rates of the embryos that reexpanded and developed to the hatching and hatched blastocyst stages were determined at, respectively, 24, 48, and 72 h after thawing. Rates of cleavage and blastocyst formation were expressed as mean ± SD and were analysed by ANOVA. The post-thaw survival rates of frozen embryos were analysed by Fisher’s exact test and chi-square test. Four replications were performed. Cleavage and blastocyst formation rates did not differ among the groups (FBS: 61.6 ± 15.1 and 22.1 ± 3.5%; 0.05% sericin: 71.6 ± 12.0 and 19.4 ± 6.7%; 0.1% sericin: 70.3 ± 4.7 and 18.4 ± 5.6%; 0.15% sericin: 66.9 ± 10.3 and 17.9 ± 6.9%, respectively). There were no significant differences in post-thaw survival rates after 24 h among the FBS (88.2%), 0.05% sericin (92.9%), 0.1% sericin (84.1%), and 0.15% sericin (93.2%) groups. However, post-thaw survival rates after 72 h in the 0.05% sericin (83.9%) and FBS (82.4%) groups were significantly higher than those in the 0.1% sericin (56.8%) and 0.15% sericin (61.4%) groups (P &lt; 0.05). These results indicate the feasibility of sericin as an alternative protein supplement for bovine embryo culture. Additionally, in this study, 0.05% sericin was shown to be the best concentration for survival of the resultant embryos after freezing and thawing.

실크 세리신 단백질을 이용한 유기 철분제의 제조 및 철분 결핍쥐에서의 생물학적 유용성

세리신을 철분과 결합력이 우수한 가수분해물을 제조하기 위하여 다양한 효소 처리를 실시하였으며 세리신 가수분해물을 이용하여 철분과 결합력을 검토하였다. 고분자인 세리신 단백질 분말을 효소 처리하지 않은 control과 비교한 결과 Flavourzyme(16.2 ㎎/mL)을 처리한 경우 유리 아미노산의 함량이 유의적으로 증가하였다. Flavourzyme 세리신 가수분해물에 각각 1,000 ppm과 2,000 ppm의 FeSO₄을 넣어 교반한 후 80%에탄올 침전 후 얻은 상등액과 침전물을 Fe 함량을 측정한 결과 유기철분 1,000 ppm의 철분의 양은 상등액(7.8 ㎍/mL)에 비해 침전(191.5 ㎍/mL)이 높은 값을 나타내며 유기철분 2,000 ppm 역시도 상등액(8.5 ㎍/mL)에 비해 침전(411.0 ㎍/mL)이 유의적으로 증가하였다. 2주간철분 결핍 식이를 투여한 쥐를 4군으로 분리한 후 형태가 다른 3종의 철분을 1주간 투여한 결과 체중증가량이나 식이 섭취율 및 식이효율을 측정한 결과 모든 투여군에서 군 간에 유의적인 차이가 없었다. 그러나 체내 흡수된 철분의 농도를 측정한 결과 혈청(2.0 ㎍/mL)과 간(47.9 ㎍/mL) 모두 무처치 대조군(DD)에서 가장 낮은 철분 농도가 관찰되었다. 형태를 달리한 철분을 투여한 모든 군에서 무처치 대조군보다 철분의 농도가 혈청 및 간에서 모두 유의적으로 증가하였다. 세리신을 이용하여 제조한 유기철분 투여군은 간에서 80.1㎍/mL, 혈청에서 4.2 ㎍/mL의 철분 농도가 관찰되었으며, 양성 대조군인 헴철 투여군에서는 간에서 70.6 ㎍/mL, 혈청에서 3.2 ㎍/mL의 철분 농도가 관찰되었으나 두 투여군 간의 유의적 차이는 없었다. 무기철분을 투여한 군(DD＋Ⅱ)보다는 간에서의 철분 함량(67.9 ㎍/mL)이 유의적으로 증가하는 경향을 나타내었으나 유기철분이나 헴철보다는 유의적인 수준에서 낮게 관찰되었다. 혈중 헤모글로빈 농도는 무처치 대조군(8.9 g/dL)에 비해 철분 처치군(DD＋HI: 12.2 g/dL, DD+OI: 12.6 g/dL, DD+Ⅱ: 12.0 g/dL)이 유의적으로 높았으나 철분의 형태에 따른 유의적 차이는 관찰되지 않았다.

The fractal self-assembly of the silk protein sericin

Silk consists primarily of two proteins—a fibrous core protein, fibroin, and a glue protein, sericin, which envelops the fibroin fibers with sticky layers thus helping in the formation of cocoon, achieved by cementing the silk fibers together. Sericin, a water soluble protein, has traditionally been discarded in silk processing, despite great potential for use as a biomaterial. Here we show that this glue protein, sericin, has the ability to form self-assembled nano and microstructures with hierarchical self-similarity across length scales in the form of a diffusion-limited, fractal assembly. Sericin obtained from two silkworms, a domesticated mulberry Bombyx mori and a wild non-mulberry Antheraea mylitta, were studied, with particular insight into its structure and morphology as it dried on a surface. High-resolution atomic force microscopy was used to image the self-assembled protein, with investigations on the various factors that influenced this process. We describe the self-assembly patterns formed by the sericin protein and analyze the images based on the theory of diffusion limited aggregation to explain the fractal nature of these architectures observed. The unique physical behavior and fractal nature of this glue protein may represent a key step in understanding its biological relevance as well as the role it plays in the assembly and formation of silks.

23. Cryopreservation of human adipose tissue-derived stem/progenitor cells using the silk protein sericin

23. Cryopreservation of human adipose tissue-derived stem/progenitor cells using the silk protein sericin

Development of mammalian factors-free medium for cell culture by using silk protein sericin

Development of mammalian factors-free medium for cell culture by using silk protein sericin

Silk gland sericin protein membranes: Fabrication and characterization for potential biotechnological applications

This study describes the potential use of silk gland sericin protein as a biocompatible natural biopolymer in its native form. The membranes were fabricated using native silk sericin protein extracted from middle silk gland of Antheraea mylitta, a non-mulberry tropical tasar silkworm without using any cross-linking agent. The fabricated membranes were biophysically characterized and optimized for cell culture. Silk sericin protein extracted from gland contained higher amount of β-sheets, which increased upon treatment with ethanol as observed by FTIR and XRD. The membranes did show robustness, good mechanical strength and high temperature stability. Cytocompatibility of the membranes was evaluated by MTT assay and cell cycle analysis using feline fibroblast cells. Morphology of growing cells was assessed by confocal microscopy that indicated normal spreading and proliferation on the silk sericin membranes. The membranes showed low inflammatory response as observed assaying TNF α release. This study reveals the potential of native silk sericin protein from silk gland as biocompatible biopolymer for potential biomedical applications.

Self-assembled silk sericin/poloxamer nanoparticles as nanocarriers of hydrophobic andhydrophilic drugs for targeted delivery

In recent times self-assembled micellar nanoparticles have been successfully employed intissue engineering for targeted drug delivery applications. In this review, silk sericin proteinfrom non-mulberry Antheraea mylitta tropical tasar silk cocoons was blended with pluronicF-127 and F-87 in the presence of solvents to achieve self-assembled micellarnanostructures capable of carrying both hydrophilic (FITC-inulin) and hydrophobic(anticancer drug paclitaxel) drugs. The fabricated nanoparticles were subsequentlycharacterized for their size distribution, drug loading capability, cellular uptake andcytotoxicity. Nanoparticle sizes ranged between 100 and 110 nm in diameter asconfirmed by dynamic light scattering. Rapid uptake of these particles into cells wasobserved in in vitro cellular uptake studies using breast cancer MCF-7 cells. In vitrocytotoxicity assay using paclitaxel-loaded nanoparticles against breast cancer cellsshowed promising results comparable to free paclitaxel drugs. Drug-encapsulatednanoparticle-induced apoptosis in MCF-7 cells was confirmed by FACS and confocalmicroscopic studies using Annexin V staining. Up-regulation of pro-apoptotic protein Bax,down-regulation of anti-apoptotic protein Bcl-2 and cleavage of regulatory proteinPARP through Western blot analysis suggested further drug-induced apoptosis incells. This study projects silk sericin protein as an alternative natural biomaterialfor fabrication of self-assembled nanoparticles in the presence of poloxamer forsuccessful delivery of both hydrophobic and hydrophilic drugs to target sites.

Rat islet culture in serum-free medium containing silk protein sericin

The development of islet cultures is desirable for successful clinical islet transplantation. Fetal bovine serum (FBS) has been used as a supplement in islet culture medium, but it may be an unsuitable supplement due recent animal health problems. We have evaluated the use of the silk protein, sericin, derived from Bombyx mori as a replacement for FBS in islet culture medium. Twenty rat islets were cultured in medium containing either sericin or FBS, or no supplement, for 14 days, during which time viable islets were counted in order to evaluate islet survival. Insulin secretion was measured in vitro by static incubation on days 3 and 7. In vivo function of cultured islets was tested by syngeneic transplantation. The islets were evaluated histologically and immunohistochemically after culture and transplantation. Ninety-five percent of islets were viable after culture for 14 days in culture medium supplemented with either FBS or sericin, while no islets survived beyond 7 days in culture without supplement. No significant differences in stimulated insulin secretion were noted between two groups of islets grown on supplemented media. Following transplantation, islets cultured in FBS or sericin rapidly reversed hyperglycemia and maintained normal glycemic control. Histologically, islets cultured with sericin displayed a well-preserved structure and strong insulin staining before and after transplantation. Serum-free medium containing sericin appears to be useful for islet culture.