Clinical application of a silk fibroin protein biologic scaffold for abdominal wall fascial reinforcement.

BACKGROUND: Preclinical studies have demonstrated that macroporous silk fibroin protein scaffolds are capable of promoting physiologically durable supportive tissue, which favors application of these engineered tissues for clinical implantation. The safety and effectiveness of a long-lasting, transitory, 510(k)-cleared purified silk fibroin biologic scaffold (SBS) are investigated for soft-tissue support and repair of the abdominal wall. METHODS: We conducted a multicenter retrospective review of all consecutive patients who underwent abdominal wall soft-tissue reinforcement with an SBS device between 2011 and 2013. Indications, comorbid conditions, surgical technique, complications, and outcomes were evaluated. RESULTS: We reviewed the records of 172 consecutive patients who received an SBS for soft-tissue support. Of those, 77 patients underwent abdominal wall fascial repair, with a mean follow-up of 18.4 ± 7.5 months. Procedures using an SBS included reinforcement of an abdominal-based flap donor site (31.2%), ventral hernia repair (53.2%), and abdominoplasty (15.6%). The overall complication rate was 6.5%, consisting of 2 wound dehiscences, 1 with device exposure, 1 seroma, 1 infection with explantation, and a perioperative bulge requiring reoperation. There were no reports of hernia. CONCLUSIONS: Postoperative complication rates after 18 months were low, and most surgical complications were managed nonoperatively on an outpatient basis without mesh removal. To our knowledge, this is the only series to report on a long-lasting, transitory SBS for abdominal wall repair and reinforcement. Procedure-specific outcome studies are warranted to delineate optimal patient selection and define potential device characteristic advantages.

Characterization of dielectrophoresis-aligned nanofibrous silk fibroin-chitosan scaffold and its interactions with endothelial cells for tissue engineering applications.

Aligned three-dimensional nanofibrous silk fibroin-chitosan (eSFCS) scaffolds were fabricated using dielectrophoresis (DEP) by investigating the effects of alternating current frequency, the presence of ions, the SF:CS ratio and the post-DEP freezing temperature. Scaffolds were characterized with polarized light microscopy to analyze SF polymer chain alignment, atomic force microscopy (AFM) to measure the apparent elastic modulus, and scanning electron microscopy and AFM to analyze scaffold topography. The interaction of human umbilical vein endothelial cells (HUVECs) with eSFCS scaffolds was assessed using immunostaining to assess cell patterning and AFM to measure the apparent elastic modulus of the cells. The eSFCS (50:50) samples prepared at 10MHz with NaCl had the highest percentage of aligned area as compared to other conditions. As DEP frequency increased from 100kHz to 10MHz, fibril sizes decreased significantly. eSFCS (50:50) scaffolds fabricated at 10MHz in the presence of 5mM NaCl had a fibril size of 77.96±4.69nm and an apparent elastic modulus of 39.9±22.4kPa. HUVECs on eSFCS scaffolds formed aligned and branched capillary-like vascular structures. The elastic modulus of HUVEC cultured on eSFCS was 6.36±2.37kPa. DEP is a potential tool for fabrication of SFCS scaffolds with aligned nanofibrous structures that can guide vasculature in tissue engineering and repair.

Decellularized tracheal matrix scaffold for tracheal tissue engineering: in vivo host response.

BACKGROUND: The authors have previously demonstrated promising results with tissue engineered trachea in vitro using decellularized matrix scaffolds. The present study aims to investigate the applicability of the construct in vivo. METHODS: Tracheae harvested from Brown Norway rats (donor) and Lewis rats (recipient) were decellularized with repeated detergent-enzymatic treatment cycles. Decellularized Brown Norway tracheal matrix scaffolds were seeded with Lewis rat stem cell-derived chondrocytes externally and tracheal epithelial cells internally to generate a bilaminated tracheal construct. Brown Norway tracheal matrix scaffolds (n = 6), Lewis rat scaffolds (n = 6), and the engineered constructs (n = 3) were implanted subcutaneously in Lewis rats and observed for 4 weeks. Fresh Brown Norway (n = 6) and Lewis rat (n = 6) tracheae were implanted as controls. Histologic analysis for macrophage, CD8, and CD4 cell infiltration was performed. RESULTS: Allogeneic decellularized matrix scaffold showed significantly decreased macrophage, CD8+ and CD4+ cell infiltration compared with tracheal allografts, and demonstrated similar level of cell infiltration to syngeneic decellularized matrix scaffold. No significant differences in macrophage infiltration were observed between syngeneic decellularized matrix scaffolds and tracheal isografts. The engineered constructs achieved complete epithelial cell coverage and preserved lumen patency; however, chondrocytes failed to repopulate the cartilaginous matrix with statically seeding stem cell on scaffold. CONCLUSIONS: Decellularized tracheal matrix scaffold did not induce significant allograft rejection or foreign body reaction in vivo. Although the construct supported reepithelialization, stem cell-derived chondrocytes failed to engraft in the heterotopic environment and represent a focus of future investigations.

Nanoparticle systems as tools to improve drug delivery and therapeutic efficacy.

Nanoparticle-based drug delivery systems are appealing because, among other properties, they are easily manufactured and have the capacity to encapsulate a wide variety of drugs, many of which are not directly miscible with water. This review classifies nanoparticles into three broad categories based upon material composition: bio-inspired systems, synthetic systems, and inorganic systems. Each has distinct properties suitable for drug delivery applications, including their structure, composition, and pharmacokinetics (including clearance and uptake mechanisms), making each uniquely suitable for certain types of drugs. Furthermore, nanoparticles can be customized, making them ideal for a variety of applications. Advantages and disadvantages of the different systems are discussed. Strategies for improving nanoparticle efficacy include adding targeting agents on the nanoparticle surface, altering the degradation profile to control drug release, or PEGylating the surface to increase circulation times and reduce immediate clearance by the kidneys. The future of nanoparticle systems seems to be focused on further improving overall patient outcome by increasing delivery accuracy to the target area.

Development of nanomaterials for bone repair and regeneration.

Bone is a nanocomposite composed of organic (mainly collagen) and inorganic (nanocrystalline hydroxyapatite) components, with a hierarchical structure ranging from nano- to macroscale. Its functions include providing mechanical support and transmitting physio-chemical and mechano-chemical cues. Clinical repair and reconstruction of bone defects has been conducted using autologous and allogeneic tissues and alloplastic materials, with functional limitations. The design and development of biomaterial scaffolds that will replace the form and function of native tissue while promoting regeneration without necrosis or scar formation is a challenging area of research. Nanomaterials and nanocomposites are promising platforms to recapitulate the organization of natural extracellular matrix for the fabrication of functional bone tissues because nanostructure provides a closer approximation to native bone architecture. Nanostructured scaffolds provide structural support for the cells and regulate cell proliferation, differentiation, and migration, which results in the formation of functional tissues. Unique properties of nanomaterials, such as increased wettability and surface area, lead to increased protein adsorption when compared with conventional biomaterials. Cell-scaffold interactions at the cell-material nanointerface may be mediated by integrin-triggered signaling pathways that affect cell behavior. The materials selection and processing techniques can affect the chemical, physical, mechanical, and cellular recognition properties of biomaterials. In this article, we focused on reviewing current fabrication techniques for nanomaterials and nanocomposites, their cell interaction properties and their application in bone tissue engineering and regeneration.

Cellular and Molecular Bioengineering: A Tipping Point.

In January of 2011, the Biomedical Engineering Society (BMES) and the Society for Physical Regulation in Biology and Medicine (SPRBM) held its inaugural Cellular and Molecular Bioengineering (CMBE) conference. The CMBE conference assembled worldwide leaders in the field of CMBE and held a very successful Round Table discussion among leaders. One of the action items was to collectively construct a white paper regarding the future of CMBE. Thus, the goal of this report is to emphasize the impact of CMBE as an emerging field, identify critical gaps in research that may be answered by the expertise of CMBE, and provide perspectives on enabling CMBE to address challenges in improving human health. Our goal is to provide constructive guidelines in shaping the future of CMBE.

Decellularized tracheal matrix scaffold for tissue engineering.

BACKGROUND: A tracheal matrix scaffold decellularized by detergent-enzymatic treatment has been shown as a promising scaffold in tracheal tissue engineering. The objectives of this study were to evaluate the impact of this technique on tracheal extracellular matrix integrity and characterize the matrix environment for recellularization. METHODS: Brown Norway rat tracheae were decellularized using a modified detergent-enzymatic treatment. Antigenicity and cellularity were monitored during processing. Glycosaminoglycan content, histoarchitecture, and mechanical properties were also evaluated. Matrix compatibility was determined by cytotoxicity assay. Surface ultrastructure of the matrix and its interaction with seeded bone marrow stem cell-derived chondrocytes and tracheal epithelial cells were examined by scanning electron microscopy. RESULTS: Rat trachea treated with five detergent-enzymatic treatment cycles demonstrated complete elimination of antigenicity. Although there was a significant loss of glycosaminoglycan (t test, p < 0.01), histoarchitecture of tracheal cartilage and basement membrane was retained after decellularization. Stiffness decreased, but sufficient compressive strength was preserved to maintain lumen patency. The decellularized matrix showed good cell compatibility and favored adhesion and growth of chondrocytes and respiratory epithelial cells, as demonstrated by scanning electron microscopy. CONCLUSIONS: At the point of complete antigen removal, detergent-enzymatic treatment altered tracheal extracellular matrix composition but preserved the major structure and adequate mechanical strength. The matrix provided a compatible and supportive environment for recellularization.

GNAS1 and PHD2 short-interfering RNA support bone regeneration in vitro and in an in vivo sheep model.

BACKGROUND: Our ability to guide cells in biomaterials for in vivo bone repair is limited and requires novel strategies. Short-interfering RNA (siRNA) allows the regulation of multiple cellular pathways. Core binding factor alpha 1 (Cbfa1) and hypoxia-inducible factor 1 (HIF-1) pathways can be modulated to direct bone formation via siRNA against guanine nucleotide-binding protein alpha-stimulating activity polypeptide 1 (siGNAS1) and prolyl hydroxylase domain-containing protein 2 (siPHD2), respectively. QUESTIONS/PURPOSES: We determined whether the administration of siGNAS1 and siPHD2 in mesenchymal stem cells (MSCs) promotes osteogenic phenotype, the dose-dependent effects of siGNAS1 on MSC differentiation to osteogenic phenotype, and whether the two siRNAs promote bone formation in vivo. METHODS: siRNAs were administered to MSCs at Day 0, and protein expression of bone-specific markers was assessed at Days 1, 2, and 4 (n = 3/group/time point). In an in vivo model using seven sheep, chambers containing silk fibroin-chitosan (SFCS) scaffolds with siRNA were implanted over the periosteum and harvested at Days 7, 21, 36, and 70 (n = 4/group/time point, except at Day 70 [n = 2]) to assess bone formation. RESULTS: siGNAS1 promoted collagen I and osteopontin expression, whereas siPHD2 had no effect in vitro. Dose-dependent effects of siGNAS1 on ALP expression were maximal at Day 1 for 10 µg/mL and Day 4 for 100 µg/mL. In vivo, by Day 70, mean bone volume increased compared to Day 7 for siGNAS1-SFCS (47.8 versus 1.8 mg/mL) and siPHD2-SFCS (61.3 versus 1.5 mg/mL). CONCLUSIONS: Both siPHD2 and siGNAS1 support bone regeneration in vivo, whereas only siGNAS1 regulates bone phenotype in MSCs in vitro.

Perichondrium directed cartilage formation in silk fibroin and chitosan blend scaffolds for tracheal transplantation.

The purpose of this study was to investigate the potential of silk fibroin and chitosan blend (SFCS) biological scaffolds for the purpose of cartilage tissue engineering with applications in tracheal tissue reconstruction. The capability of these scaffolds as cell carrier systems for chondrocytes was determined in vitro and cartilage generation in vivo on engineered chondrocyte-scaffold constructs with and without a perichondrium wrapping was tested in an in vivo nude mouse model. SFCS scaffolds supported chondrocyte adhesion, proliferation, and differentiation, determined as features of the cells based on the spherical cell morphology, increased accumulation of glycosaminoglycans, and increased collagen type II deposition with time within the scaffold framework. Perichondrium wrapping significantly (P<0.001) improved chondrogenesis within the cell-scaffold constructs in vivo. In vivo implantation for 6weeks did not generate cartilage structures resembling native trachea, although cartilage-like structures were present. The mechanical properties of the regenerated tissue increased due to the deposition of chondrogenic matrix within the SFCS scaffold structural framework of the trachea. The support of chondrogenesis by the SFCS tubular scaffold construct resulted in a mechanically sound structure and thus is a step towards an engineered trachea that could potentially support the growth of an epithelial lining resulting in a tracheal transplant with properties resembling those of the fully functional native trachea.

Repair and reconstruction of a resected tumor defect using a composite of tissue flap-nanotherapeutic-silk fibroin and chitosan scaffold.

A multifaceted strategy using a composite of anti-cancer nanotherapeutic and natural biomaterials silk fibroin (SF) and chitosan (CS) blend scaffolds was investigated for the treatment of a tissue defect post-tumor resection by providing local release of the therapeutic and filling of the defect site with the regenerative bioscaffolds. The scaffold-emodin nanoparticle composites were fabricated and characterized for drug entrapment and release, mechanical strength, and efficacy against GILM2 breast cancer cells in vitro and in vivo in a rat tumor model. Emodin nanoparticles were embedded in SF and SFCS scaffolds and the amount of emodin entrapment was a function of the scaffold composition and emodin loading concentration. In vitro, there was a burst release of emodin from all scaffolds during the first 2 days though it was detected even after 24 days. Increase in emodin concentration in the scaffolds decreased the overall elastic modulus and ultimate tensile strength of the scaffolds. After 6 weeks of in vivo implantation, the cell density (p < 0.05) and percent degradation (p < 0.01) within the remodeled no emodin SFCS scaffold was significantly higher than the emodin loaded SFCS scaffolds, although there was no significant difference in the amount of collagen deposition in the regenerated SFCS scaffold. The presence and release of emodin from the SFCS scaffolds inhibited the integration of SFCS into the adjacent tumor due to the formation of an interfacial barrier of connective tissue that was lacking in emodin-free SFCS scaffolds. While no significant difference in tumor size was observed between the in vivo tested groups, tumors treated with emodin loaded SFCS scaffolds had decreased presence and size and similar regeneration of new tissue as compared to no emodin SFCS scaffolds.

Human versus non-cross-linked porcine acellular dermal matrix used for ventral hernia repair: comparison of in vivo fibrovascular remodeling and mechanical repair strength.

BACKGROUND: Human acellular dermal matrix (HADM) and non-cross-linked porcine acellular dermal matrix (ncl-PADM) are clinically useful for complex ventral hernia repair. Direct comparisons between the two in vivo are lacking, however. This study compared clinically relevant early outcomes with these bioprosthetic materials when used for ventral hernia repair. METHODS: Seventy-two guinea pigs underwent inlay repair of surgically created hernias with HADM (n = 37) or ncl-PADM (n = 35). Repair sites were harvested at 1, 2, or 4 weeks postoperatively. Adhesions were graded and quantified. Mechanical testing and histologic and immunohistologic (factor VIII) analyses of cellular and vascular infiltration were performed. RESULTS: No infections or recurrent hernias occurred. No difference was observed in mean adhesion surface area or tenacity between groups. Mean cellular infiltration (p < 0.002, weeks 1 and 4; p < 0.006, week 2) and vascular infiltration (p < 0.0003, week 1; p < 0.0001, weeks 2 and 4) were greater in HADM. Ultimate tensile strength at the implant-musculofascia interface increased over time with both materials, but no difference was observed at 4 weeks. The mean ultimate tensile strength of explanted ncl-PADM itself was consistently greater than that of HADM. The elastic modulus (stiffness) did not differ between groups at the interface but was greater in explanted ncl-PADM (p < 0.0001, weeks 1 and 2; p < 0.02, week 4). CONCLUSIONS: Both HADM and ncl-PADM become infiltrated with host cells and blood vessels within 4 weeks and have similar musculofascia-bioprosthetic interface strength. However, HADM has greater cellular and vascular infiltration. Longer-term studies will help determine whether later differences in material strength, stiffness, and remodeling affect hernia and/or bulge incidence.

Comparison of cross-linked and non-cross-linked porcine acellular dermal matrices for ventral hernia repair.

BACKGROUND: Porcine acellular dermal matrices (PADMs) have been used clinically for abdominal wall repair. The newer non-cross-linked PADMs, however, have not been directly compared with cross-linked PADMs. We hypothesized that chemical cross-linking affects the biologic host response to PADMs used to repair ventral hernias. STUDY DESIGN: Fifty-eight guinea pigs underwent inlay repair of surgically created ventral hernias using cross-linked or non-cross-linked PADM. After animals were sacrificed at 1, 2, or 4 weeks, the tenacity of and surface area involved by adhesions to the repair sites were measured. Sections of the repair sites, including the bioprosthesis-musculofascia interface, underwent histologic analysis of cellular and vascular infiltration plus mechanical testing. RESULTS: Compared with cross-linked PADM repairs, non-cross-linked PADM repairs had a significantly lower mean tenacity grade of adhesions at all timepoints and mean adhesion surface area at week 1. Mean cellular and vascular densities were significantly higher in non-cross-linked PADM at all timepoints. Cells and vessels readily infiltrated into the center of non-cross-linked PADM, but encapsulated cross-linked PADM, with a paucity of penetration into it. Mechanical properties were similar for the two PADMs (in isolation) at all timepoints; however, at the bioprosthesis-musculofascia interface, both elastic modulus and ultimate tensile strength were significantly higher at weeks 1 and 2 for non-cross-linked PADM. CONCLUSIONS: Non-cross-linked PADM is rapidly infiltrated with host cells and vessels; cross-linked PADM becomes encapsulated. Non-cross-linked PADM causes weaker adhesions to repair sites while increasing the mechanical strength of the bioprosthesis-musculofascia interface at early timepoints. Non-cross-linked PADM may have early clinical advantages over cross-linked PADM for bioprosthetic abdominal wall reconstruction.

Silk fibroin-derived nanoparticles for biomedical applications.

The treatment of disease in the future will be influenced by the ability to produce therapeutic formulations that have high availability at the disease site, sustained and long-term release, with minimal to no toxicity to healthy tissues. Biologically derived delivery systems offer promise in this regard owing to minimization of adverse effects while increasing the efficacy of the entrapped therapeutic. Silk fibroin nanoparticles overcome barriers set by synthetic nondegradable nanoparticles made of silicone, polyethylene glycol and degradable polylactic acid-polyglycolic acid polymers. Silk fibroin-mediated delivery has demonstrated high efficacy in breast cancer cells. While the targeting is associated with the specificity of entrapped therapeutic for the diseased cells, silk fibroin-derived particles enhance intracellular uptake and retention resulting in downmodulation of more than one pathway due to longer availability of the therapeutic. The mechanism of targeting for the nanoparticle is based on the silk fibroin composition, beta-sheet structure and self-assembly into beta-barrels.

Endothelial and stem cell interactions on dielectrophoretically aligned fibrous silk fibroin-chitosan scaffolds.

Regenerative tissue engineering requires biomaterials that would mimic structure and composition of the extracellular matrix to facilitate cell infiltration, differentiation, and vascularization. Engineered scaffolds composed of natural biomaterials silk fibroin (SF) and chitosan (CS) blend were fabricated to achieve fibrillar nano-structures aligned in three-dimensions using the technique of dielectrophoresis. The effect of scaffold properties on adhesion and migration of human adipose-derived stem cells (hASC) and endothelial cells (HUVEC) was studied on SFCS (micro-structure, unaligned) and engineered SFCS (E-SFCS; nano-structure, aligned). E-SFCS constituted of a nano-featured fibrillar sheets, whereas SFCS sheets had a smooth morphology with unaligned micro-fibrillar extensions at the ends. Adhesion of hASC to either scaffolds occurred within 30 min and was higher than HUVEC adhesion. The percentage of moving cells and average speed was highest for hASC on SFCS scaffold as compared to hASC cocultured with HUVEC. HUVEC interactions with hASC appeared to slow the speed of hASC migration (in coculture) on both scaffolds. It is concluded that the guidance of cells for regenerative tissue engineering using SFCS scaffolds requires a fine balance between cell-cell interactions that affect the migration speed of cells and the surface characteristics that affects the overall adhesion and direction of migration.

Adhesion, migration and mechanics of human adipose-tissue-derived stem cells on silk fibroin-chitosan matrix.

Silk fibroin-chitosan (SFCS) scaffold is a naturally derived biocompatible matrix with potential reconstructive surgical applications. In this study, human adipose-derived mesenchymal stem cells (ASCs) were seeded on SFCS scaffolds and cell attachment was characterized by fluorescence, confocal, time-lapse, atomic force, and scanning electron microscopy (SEM) studies. Adhesion of ASCs on SFCS was 39.4 + or - 4.8% at 15 min, increasing to 92.8+/-1.5% at 120 min. ASC adhered at regions of architectural complexity and infiltrate into three-dimensional scaffold. Time-lapse confocal studies indicated a mean ASC speed on SFCS of 18.47+/-2.7 microm h(-1) and a mean persistence time of 41.4 + or - 9.3 min over a 2.75 h study period. Cytokinetic and SEM studies demonstrated ASC-ASC interaction via microvillus extensions. The apparent elastic modulus was significantly higher (p<0.0001) for ASCs seeded on SFCS (69.0 + or - 9.0 kPa) than on glass (6.1 + or - 0.4 kPa). Also, cytoskeleton F-actin fiber density was higher (p<0.05) for ASC seeded on SFCS (0.42 + or - 0.02 fibers microm(-1)) than on glass-seeded controls (0.24 + or - 0.03 fibers microm(-1)). Hence, SFCS scaffold facilitates mesenchymal stem cell attachment, migration, three-dimensional infiltration, and cell-cell interaction. This study showed the potential use of SFCS as a local carrier for autologous stem cells for reconstructive surgery application.

Non-cross-linked porcine acellular dermal matrices for abdominal wall reconstruction.

BACKGROUND: Non-cross-linked porcine acellular dermal matrices have been used clinically for abdominal wall repair; however, their biologic and mechanical properties and propensity to form visceral adhesions have not been studied. The authors hypothesized that their use would result in fewer, weaker visceral adhesions than polypropylene mesh when used to repair ventral hernias and form a strong interface with the surrounding musculofascia. METHODS: Thirty-four guinea pigs underwent inlay repair of surgically created ventral hernias using polypropylene mesh, porcine acellular dermal matrix, or a composite of the two. The animals were killed at 4 weeks, and the adhesion tenacity grade and surface area of the repair site involved by adhesions were measured. Sections of the repair sites, including the implant-musculofascia interface, underwent histologic analysis and uniaxial mechanical testing. RESULTS: The incidence of bowel adhesions to the repair site was significantly lower with the dermal matrix (8 percent, p < 0.01) and the matrix/mesh combination (0 percent, p < 0.001) than with polypropylene mesh alone (70 percent). The repairs made with the matrix or the matrix/mesh combination, compared with the polypropylene mesh repairs, had significantly lower mean adhesion surface areas [12.8 percent (p < 0.001), 9.2 percent (p < 0.001), and 79.9 percent] and grades [0.6 (p < 0.001), 0.6 (p < 0.001), and 2.9]. The dermal matrix underwent robust cellular and vascular infiltration. The ultimate tensile strength at the implant-musculofascia interface was similar in all groups. CONCLUSIONS: Porcine acellular dermal matrix becomes incorporated into the host tissue and causes fewer adhesions to repair sites than does polypropylene mesh, with similar implant-musculofascia interface strength. It also inhibits adhesions to adjacent dermal matrix in the combination repairs. It has distinct advantages over polypropylene mesh for complex abdominal wall repairs, particularly when material placement directly over bowel is unavoidable.

In vivo bone formation in silk fibroin and chitosan blend scaffolds via ectopically grafted periosteum as a cell source: a pilot study.

Reconstruction of a critical size bone defect in the head and neck after trauma or tumor resection remains challenging. While certain defects, such as isolated orbital floor fractures, may be reconstructed with alloplastic biomaterials, larger defects or those involving load bearing bones usually require autologous tissue reconstruction. Vascularized bone free flaps remain the gold standard for large bone defects of the head and neck. These are generally lengthy, complicated, multi-step procedures that require subspecialty expertise to assure optimal outcomes.1 Invariably any procedure where autologous bone is harvested carries with it donor site morbidity.2 To spare the patient this additional morbidity and avoid potential complications associated with the harvest of this tissue, an alternative source for bone that would be sufficient to fill a critical-sized defect is needed.

Fabrication and characterization of silk fibroin-derived curcumin nanoparticles for cancer therapy.

Biologically derived nanoparticles (<100 nm) were fabricated for local and sustained therapeutic curcumin delivery to cancer cells. Silk fibroin (SF) and chitosan (CS) polymers were blended noncovalently to encapsulate curcumin in various proportions of SF and CS (75:25, 50:50, and 25:75 SF:CS) or pure SF at two concentrations (0.1% w/v and 10% w/v) using the devised capillary-microdot technique. Curcumin-polymer conjugates were frozen, lyophilized, crystallized, suspended in phosphate-buffered saline for characterization, and tested for efficacy against breast cancer cells. All nanoparticle formulations except 0.1% w/v 50:50 SFCS were less than 100 nm in size as determined with the transmission electron microscopy. The entrapment and release of curcumin over eight days was highest for SF-derived nanoparticles as compared to all SFCS blends. The uptake and efficacy of SF-coated curcumin was significantly higher (p < 0.001) than SFCS-coated curcumin in both low and high Her2/neu expressing breast cancer cells. Interestingly, the uptake of curcumin was highest for the high Her2/neu expressing breast cancer cells when delivered with a 10% w/v SF coating as compared to other formulations. In conclusion, SF-derived curcumin nanoparticles show higher efficacy against breast cancer cells and have the potential to treat in vivo breast tumors by local, sustained, and long-term therapeutic delivery as a biodegradable system.

Fabrication and characterization of silk-fibroin-coated quantum dots.

We report a novel technique of directly coating colloidal CdSe/ZnS core/shell quantum dots (QDs) with silk fibroin (SF), a protein derived from the Bombyx mori silk worm. The approach results in protein-modified QDs with little or no particle aggregation, and mitigates the issue of biocompatibility. QDs have desirable optical properties, such as narrow-band emission, broadband absorption, high quantum yield, and high resistance to photobleaching. SF is a fibrous protein polymer with a biomimetic peptide sequence, water and oxygen permeability, low inflammatory response, no thrombogenecity, and cellular biocompatibility, which are desirable properties for in vivo delivery. Combining the unique properties of QDs with the biocompatibility profile of SF, the approach produces particles representing a powerful tool for numerous in vivo and in vitro applications. The design and preparation of these protein-modified QDs conjugates is reported along with functional characterization using luminescence, transmission electron microscope (TEM), and atomic force microscope (AFM). Additionally, we report results obtained using the QDs conjugates as a fluorescent label for bioimaging HEYA8 ovarian cancer cells.

IFATS collection: Human adipose-derived stem cells seeded on a silk fibroin-chitosan scaffold enhance wound repair in a murine soft tissue injury model.

Soft tissue loss presents an ongoing challenge in reconstructive surgery. Local stem cell application has recently been suggested as a possible novel therapy. In the present study we evaluated the potential of a silk fibroin-chitosan (SFCS) scaffold serving as a delivery vehicle for human adipose-derived stem cells (ASCs) in a murine soft tissue injury model. Green fluorescent protein (GFP)-labeled ASCs were seeded on SFCS scaffolds at a density of 1 x 10(5) ASCs per cm(2) for 48 hours and then suture-inlaid to a 6-mm, full-thickness skin defect in 6-week-old male athymic mice. Wound healing was tracked for 2 weeks by planimetry. Histology was evaluated at 2 and 4 weeks. Our data show that the extent of wound closure was significantly enhanced in the ASC-SFCS group versus SFCS and no-graft controls at postoperative day 8 (90% +/- 3% closure vs. 75% +/- 11% and 55% +/- 17%, respectively). Microvessel density at wound bed biopsy sites from 2 weeks postoperative was significantly higher in the ASC-SFCS group versus SFCS alone (7.5 +/- 1.1 vs. 5.1 +/- 1.0 vessels per high-power field). Engrafted stem cells were positive for the fibroblastic marker heat shock protein 47, smooth muscle actin, and von Willebrand factor at both 2 and 4 weeks. GFP-positive stem cells were also found to differentiate into epidermal epithelial cells at 4 weeks postoperative. In conclusion, human adipose-derived stem cells seeded on a silk fibroin-chitosan scaffold enhance wound healing and show differentiation into fibrovascular, endothelial, and epithelial components of restored tissue.