Pornanong Aramwit

The effects of sericin cream on wound healing in rats

Sericin has good hydrophilic properties, compatibility, and biodegradation, it can be used as a wound-healing agent. We evaluated the effects of sericin on wound healing and wound size reduction using rats by generating two full-thickness skin wounds on the dorsum. Group 1 animals were treated with Betadine® on left-side (control) wounds and, with 8% sericin cream on right-side (treated) wounds. Group 2, cream base (formula control) and 8% sericin cream (treated) were topically applied to left-, and right-side wounds respectively. Sericin-treated wounds had much smaller inflammatory reactions, and wound-size reduction was much greater than in the control throughout the inspection period. Mean time in days for 90% healing from sericin-treated wounds was also much less than for cream base-treated wounds. Histological examination after 15 d of treatment with 8% sericin cream revealed complete healing, no ulceration, and an increase in collagen as compared to cream base-treated wounds, which showed some ulceration and acute inflammatory exudative materials.

The effect of sericin from various extraction methods on cell viability and collagen production.

Silk sericin (SS) can accelerate cell proliferation and attachment; however, SS can be extracted by various methods, which result in SS exhibiting different physical and biological properties. We found that SS produced from various extraction methods has different molecular weights, zeta potential, particle size and amino acid content. The MTT assay indicated that SS from all extraction methods had no toxicity to mouse fibroblast cells at concentrations up to 40 μg/mL after 24 h incubation, but SS obtained from some extraction methods can be toxic at higher concentrations. Heat-degraded SS was the least toxic to cells and activated the highest collagen production, while urea-extracted SS showed the lowest cell viability and collagen production. SS from urea extraction was severely harmful to cells at concentrations higher than 100 μg/mL. SS from all extraction methods could still promote collagen production in a concentration-dependent manner, even at high concentrations that are toxic to cells.

Nanotechnology in drug delivery

Fundamentals of Nanotechnology in Drug Delivery.- Physicochemical Principles of Nanosized Drug Delivery Systems.- Block Copolymer Synthesis for Nanoscale Drug and Gene Delivery.- Supercritical Fluid Technology for Nanotechnology in Drug Delivery.- Nanotubes, Nanorods, Nanofibers, and Fullerenes for Nanoscale Drug Delivery.- Drug Loading into and In Vitro Release from Nanosized Drug Delivery Systems.- Nanotechnology-Based Biosensors in Drug Delivery.- Biopharmaceutical, Physiological, and Clinical Considerations for Nanotechnology in Drug Delivery.- Nanomaterials and Biocompatibility: BioMEMS and Dendrimers.- Nanomaterials and Biocompatibility: Carbon Nanotubes and Fullerenes.- Factors Controlling Pharmacokinetics of Intravenously Injected Nanoparticulate Systems.- Controlled Release and Nanotechnology.- Nanotechnology for Intracellular Delivery and Targeting.- Nanotechnology for the Delivery of Small Molecules, Proteins and Nucleic Acids.- Nano-sized Advanced Delivery Systems as Parenteral Formulation Strategies for Hydrophobic Anti-cancer Drugs.- Engineering of Amphiphilic Block Copolymers for Drug and Gene Delivery.- PAMAM Dendrimers as Nanoscale Oral Drug Delivery Systems.- Nanoemulsions for Intravenous Drug Delivery.- Nanotechnology for Cancer Chemotherapy.- Nanotechnology for Cancer Vaccine Delivery.- Stimuli-Sensitive Nanotechnology for Drug Delivery.- A Look to the Future of Nanotechnology in Drug Delivery.- Nanotechnology in Drug Delivery: Past, Present, and Future.- Nanotechnology in Drug Development and Life Cycle Management.- Nanopharmaceuticals: Challenges and Regulatory Perspective.

Monitoring of inflammatory mediators induced by silk sericin.

Silk proteins have been shown to be good candidates for biomedical materials. However, there have been some reports regarding immunological and allergic responses to silk sericin. Our objective was to investigate the inflammatory mediators induced by sericin both in vitro and in vivo. Mouse monocyte and alveolar macrophage cell lines were used for monitoring levels of interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha generated after activation by sericin at concentrations of 0.2-1.0 mg/mL. The amounts of TNF-alpha and IL-1beta produced by both cell lines corresponded, in a dose-dependent manner, with the sericin concentration in the culture medium. The levels of TNF-alpha and IL-1beta generated after sericin activation by macrophage cells were higher than those generated by monocytes. However, these cytokine levels would not cascade to other inflammatory effects. Inflammatory mediators were also monitored from sericin-treated, cream base-treated and normal saline-soaked full-thickness rat excisions. Using wound size measurements and ELISA assays, sericin-treated wounds were shown to heal faster and had lower levels of inflammatory mediators, as compared with the cream base-treated and normal saline-soaked wounds. It can be concluded that sericin promotes the wound healing process without causing inflammation.

Potential applications of silk sericin, a natural protein from textile industry by-products

Silk is composed of two major proteins, fibroin (fibrous protein) and sericin (globular, gumming protein). Fibroin has been used in textile manufacturing and for several biomaterial applications, whereas sericin is considered a waste material in the textile industry. Sericin has recently been found to activate the proliferation of several cell-lines and has also shown various biological activities. Sericin can form a gel by itself; however, after mixing with other polymers and cross-linking it can form a film or a scaffold with good characteristics that can be used in the cosmetic and pharmaceutical industries. Sericin is proven to cause no immunological responses, which has resulted in a more acceptable material for biological applications.

Formulation and characterization of silk sericin–PVA scaffold crosslinked with genipin

A porous-three-dimensional scaffold shows several advantages in terms of tissue engineering since it can provide a framework for cells to attach, proliferate and form an extracellular matrix. Sericin, a by-product from the silk industry, can form a three-dimensional scaffold with PVA after freeze-drying but has a fragile structure. Glycerin (as a plasticizer) and genipin (a crosslinking agent) are necessary to make a strong and stable matrix. Our objective was to investigate the properties of a three-dimensional silk sericin and PVA scaffold with and without glycerin and genipin at various concentrations. SEM showed that adding glycerin into scaffold gave better uniformity and porosity. Smaller pore sizes and better uniformity were found as the concentration of genipin in the scaffold increased. The results of FTIR indicated that glycerin retained a high moisture content and had a major effect at 3286 cm(-1), indicating the presence of water molecule in the matrix structure. Adding genipin into the scaffold resulted in a higher degree of crosslinking or fewer free ∈-amino groups, as shown by the decrease in the stretching (=C-H) peak and absorption peaks around 1370-1650 cm(-1), respectively. The sericin/PVA scaffold had a low water sorption capacity, but adding glycerin significantly increased this property. Genipin further enhanced the moisture absorption capacity of the scaffold and extended the time taken to reach equilibrium. After immersing the sericin/PVA scaffold into purified water, the scaffold completely dissolved within an hour, whereas the scaffolds containing glycerin or glycerin with 0.1% genipin swelled 8 and 11 times, respectively, compared with the initial stage after 6h of immersion. In terms of mechanical properties, the sericin/PVA/glycerin scaffold exhibited a similar compressive strength to the scaffold with a high genipin concentration, whereas a low concentration of genipin softened and reduced the compressive strength of the scaffold. A small amount of sericin was released from the scaffold and a higher concentration of genipin, resulting in less protein leaching compared to non-crosslinked sericin/PVA. The fraction of protein released from the sericin/PVA/glycerin scaffold was about 4%, with values of about 1 and 0.04% in the case of scaffolds with 0.01 and 0.1% genipin, respectively. All results indicated that the composition of the scaffolds had a significant effect on their physical properties, and that can easily be tuned to obtain scaffolds suitable for biological applications.

An innovative bi-layered wound dressing made of silk and gelatin for accelerated wound healing

In this study, the novel silk fibroin-based bi-layered wound dressing was developed. Wax-coated silk fibroin woven fabric was introduced as a non-adhesive layer while the sponge made of sericin and glutaraldehyde-crosslinked silk fibroin/gelatin was fabricated as a bioactive layer. Wax-coated silk fibroin fabrics showed improved mechanical properties compared with the non-coated fabrics, but less adhesive than the commercial wound dressing mesh. This confirmed by results of peel test on both the partial- and full-thickness wounds. The sericin-silk fibroin/gelatin spongy bioactive layers showed homogeneous porous structure and controllable biodegradation depending on the degree of crosslinking. The bi-layered wound dressings supported the attachment and proliferation of L929 mouse fibroblasts, particularly for the silk fibroin/gelatin ratio of 20/80 and 0.02% GA crosslinked. Furthermore, we proved that the bi-layered wound dressings promoted wound healing in full-thickness wounds, comparing with the clinically used wound dressing. The wounds treated with the bi-layered wound dressings showed the greater extent of wound size reduction, epithelialization, and collagen formation. The superior properties of the silk fibroin-based bi-layered wound dressings compared with those of the clinically used wound dressings were less adhesive and had improved biological functions to promote cell activities and wound healing. This novel bi-layered wound dressing should be a good candidate for the healing of full-thickness wounds.

The Effect of Sericin with Variable Amino-Acid Content from Different Silk Strains on the Production of Collagen and Nitric Oxide

Although silk sericin (SS) enhances the growth and attachment of fibroblast cells, its toxicity remains questionable. We investigated the effect of SS extracted by heat with variable amino-acid content on in vitro collagen promotion and nitric oxide synthesis. After 24 h of incubation, SS, especially from the Chul 1/1 strain which has the most methionine and cysteine content, enhanced fibroblast growth. The molecular mass of heat-extracted SS from these three strains showed a slightly different range, but within 20–200 kDa, which were all identified as sericin. SS from all strains promoted type-I collagen production in a concentration-dependent manner, while SS from Chul 1/1 strain could induce the highest amount of collagen synthesis when compared to SS from other strains. Nitric oxide was found in the culture medium after activation by SS from the Chul 1/1 strain but reached a level that was not toxic to the cells. We conclude that SS is not toxic to fibroblast cells. Moreover, methionine and cysteine content in SS are important factors to promote cell growth and collagen synthesis.

Properties and antityrosinase activity of sericin from various extraction methods.

The present study investigated the chemical properties and antityrosinase activities of SS (silk sericin) extracted from different Thai silk strains via various extraction methods. Different silk strains contain distinct SS with various amino acid compositions, which are significantly influenced by the extraction method used. Urea extraction of SS was the only method that provided clearly distinguishable bands and had the most significant impact on SS conformation as illustrated by FTIR (Fourier‐transform infrared) spectra. The use of urea or either acidic or alkaline chemicals in the extraction process also influenced SS thermal behaviour. With regard to biological activity, SS extracted using urea exhibited the highest antityrosinase activity, whereas alkali‐degraded SS showed no inhibition of mushroom tyrosinase. Pigments, primarily flavonoids and carotenoids from silk cocoons, were also found to enhance tyrosinase inhibition of SS.

Development of ethyl alcohol-precipitated silk sericin/polyvinyl alcohol scaffolds for accelerated healing of full-thickness wounds.

Silk sericin has been recently reported for its advantageous biological properties to promote wound healing. In this study, we established that the ethyl alcohol (EtOH) could be used to precipitate sericin and form the stable sericin/polyvinyl alcohol (PVA) scaffolds without the crosslinking. The sericin/PVA scaffolds were fabricated via freeze-drying and subsequently precipitating in various concentrations of EtOH. The EtOH-precipitated sericin/PVA scaffolds showed denser structure, higher compressive modulus, but lower water swelling ability than the non-precipitated scaffolds. Sericin could be released from the EtOH-precipitated sericin/PVA scaffolds in a sustained manner. After cultured with L929 mouse fibroblasts, the 70 vol% EtOH-precipitated sericin/PVA scaffolds showed the highest potential to promote cell proliferation. After applied to the full-thickness wounds of rats, the 70 vol% EtOH-precipitated sericin/PVA scaffolds showed significantly higher percentage of wound size reduction and higher extent of type III collagen formation and epithelialization, compared with the control scaffolds without sericin. The accelerated wound healing by the 70 vol% EtOH-precipitated sericin/PVA scaffolds was possibly due to (1) the bioactivity of sericin itself to promote wound healing, (2) the sustained release of precipitated sericin from the scaffolds, and (3) the activation and recruitment of wound healing-macrophages by sericin to the wounds. This finding suggested that the EtOH-precipitated sericin/PVA scaffolds were more effective for the wound healing, comparing with the EtOH-precipitated PVA scaffolds without sericin.