Dual-functional bioactive silk sericin for osteoblast responses and osteomyelitis treatment

Silk Sericin and Its Effect on Skin Wound Healing: A State of the Art

Despite the significant progress in wound healing, chronic skin wounds remain a challenge for today's medicine. Due to the growing popularity of natural materials, silk protein-based dressings are gaining more attention in this field. Most studies refer to silk fibroin because sericin has been considered a waste product for years. However, sericin is also worth noting. Sericin-based dressings are mainly studied in cell cultures or animals. Sericin is the dressings' main component or can be included in more complex, advanced biomaterials. Recent studies highlight sericin's important role, noting its biocompatibility, biodegradability, and beneficial effects in skin wound healing, such as antibacterial activity, antioxidant and anti-inflammatory effects, or angiogenic properties. Developing sericin-based biomaterials is often simple, free of toxic by-products, and inexpensive, requiring no highly sophisticated apparatus. As a result, sericin-based dressings can be widely used in wound healing and have low environmental impact. However, the literature in this area is further limited. The following review collects and describes recent studies showing silk sericin's influence on skin wound healing.

A comprehensive review of recent advances in silk sericin: Extraction approaches, structure, biochemical characterization, and biomedical applications

Silks are natural polymers that have been widely used for centuries. Silk consists of a filament core protein, termed fibroin, and a glue-like coating substance formed of sericin (SER) proteins. This protein is extracted from the silkworm cocoons (particularly Bombyx mori) and is mainly composed of amino acids like glycine, serine, aspartic acid, and threonine. Silk SER can be obtained using numerous methods, including enzymatic extraction, high-temperature, autoclaving, ethanol precipitation, cross-linking, and utilizing acidic, alkali, or neutral aqueous solutions. Given the versatility and outstanding properties of SER, it is widely fabricated to produce sponges, films, and hydrogels for further use in diverse biomedical applications. Hence, many authors reported that SER benefits cell proliferation, tissue engineering, and skin tissue restoration thanks to its moisturizing features, antioxidant and anti-inflammatory properties, and mitogenic effect on mammalian cells. Remarkably, SER is used in drug delivery depending on its chemical reactivity and pH-responsiveness. These unique features of SER enhance the bioactivity of drugs, facilitating the fabrication of biomedical materials at nano- and microscales, hydrogels, and conjugated molecules. This review thoroughly outlines the extraction techniques, biological properties, and respective biomedical applications of SER.

Relevant Properties and Potential Applications of Sericin in Bone Regeneration

The potential of sericin, a protein derived from silkworms, is explored in bone graft applications. Sericin's biocompatibility, hydrophilic nature, and cost-effectiveness make it a promising candidate for enhancing traditional graft materials. Its antioxidant, anti-inflammatory, and UV-resistant properties contribute to a healthier bone-healing environment, and its incorporation into 3D-printed grafts could lead to personalized medical solutions. However, despite these promising attributes, there are still gaps in our understanding. The precise mechanism through which sericin influences bone cell growth and healing is not fully understood, and more comprehensive clinical trials are needed to confirm its long-term biocompatibility in humans. Furthermore, the best methods for incorporating sericin into existing graft materials are still under investigation, and potential allergic reactions or immune responses to sericin need further study.

Molecular weight and molecular weight distribution of sericin protein extracted from cocoon waste of <i>Bombyx mori</i>

Silk sericin comprises a globular water-soluble protein that surrounds silk fibres, sticking them together and providing cocoon adhesion. Sericin was isolated from the extract solution in two ways: the first sample was obtained by concentrating the filtered extract at low pressure (SLP); the second sample was obtained by ultrafiltration (SUF) using a membrane. In this work, the size exclusion-high-performance liquid chromatography involving viscometry and refractive index detectors was used to determine the molecular weight and conformation of sericin polypeptides obtained from cocoons of the Bombyx mori silkworm. The aggregation processes of silk sericin protein under various isolation conditions from the solution were considered. It was shown that sericin macromolecules are present as a monodisperse polypeptide at low concentrations, which aggregates at concentrations greater than 1–2 mg/ml. The obtained data indicate that, along with the parameters of the extraction process, the conditions for its isolation from the solution, including temperature, pressure and degree of concentration, affect the molecular weight and aggregative behaviour of the protein. The results confirm and complement previously obtained data on the influence of various factors on the association of protein macromolecules in solution. The resulting sericin fractions can find many applications, including materials for tissue engineering, coatings for surface modification, cell culture media, cosmetics, as well as food additives and medical biomaterials.

The prevalence and antibiotic susceptibility of Staphylococcus spp. on ocular surfaces of fighting bulls (Bos indicus) in Thailand

Background and Aim

fighting bulls have a high risk of eye injuries, and opportunistic conjunctival bacterial flora may cause subsequent eye diseases. There is little information about the ocular health care of fighting bulls in Thailand. Thus, this study aimed to estimate the prevalence of Staphylococcus spp. from the eyes of fighting bulls and investigate their antimicrobial susceptibility.

Materials and Methods

The samples were collected from the right conjunctival sacs of 105 fighting bulls. Biochemical tests and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry were used to identify bacteria to genus and species levels. Antimicrobial susceptibility was tested by agar disk diffusion.

Results

Staphylococcus spp. (36.84%, 56/152) were the most detected bacteria. The most prevalent Staphylococcus spp. was Staphylococcus chromogenes (37.50%, 21/56). The susceptibility test revealed that all isolates were susceptible to sulfamethoxazole/trimethoprim (56/56, 100%) and most were susceptible to chloramphenicol and gentamicin (54/56, 96.43%). The highest resistance rates were seen for tetracycline and doxycycline (23.21%, 13/56) followed by erythromycin (19.64%, 11/56). In addition, S. chromogenes isolates were evaluated for their ability to produce biofilms by a quantitative biofilm production assay. A total of 21 isolates exhibited biofilm production, independent of their antimicrobial susceptibility. Three multidrug-resistant isolates were found, including two Staphylococcus epidermidis isolates and a single S. chromogenes isolate.

Conclusion

As antimicrobial resistant bacteria were detected on the eye surface, veterinarians should always conduct antimicrobial susceptibility testing before using antimicrobial agents. The results from this study will help to improve the standard of eye treatment for fighting bulls in Thailand.

Injectable Hydrogel Based on Gellan Gum/Silk Sericin for Application as a Retinal Pigment Epithelium Cell Carrier

The damage to retinal pigment epithelium (RPE) cells can lead to vision loss and permanent blindness. Therefore, an effective therapeutic strategy has emerged to replace damaged cells through RPE cell delivery. In this study, we fabricated injectable gellan gum (GG)/silk sericin (SS) hydrogels as a cell carrier by blending GG and SS. To determine the appropriate concentration of SS for human RPE ARPE-19, 0, 0.05, 0.1, and 0.5% (w/v) of SS solution were blended in 1% (w/v) GG solution (GG/SS 0%, GG/SS 0.05%, GG/SS 0.1%, and GG/SS 0.5%, respectively). The physical and chemical properties were measured through Fourier-transform infrared spectroscopy, scanning electron microscopy, mass swelling, and weight loss. Also, viscosity, injection force, and compressive tests were used to evaluate mechanical characteristics. Cell proliferation and differentiation of ARPE-19 were evaluated using quantitative dsDNA analysis and real-time polymerase chain reaction, respectively. The addition of SS gave GG/SS hydrogels a compressive strength similar to that of natural RPE tissue, which may well support the growth of RPE and enhance cell proliferation and differentiation. In particular, the GG/SS 0.5% hydrogel showed the most similar compressive strength (about 10 kPa) and exhibited the highest gene expression related to ARPE-19 cell proliferation. These results indicate that GG/SS 0.5% hydrogels can be a promising biomaterial for cell delivery in retina tissue engineering.

Silk Sericin: A Promising Sustainable Biomaterial for Biomedical and Pharmaceutical Applications

Silk is a natural composite fiber composed mainly of hydrophobic fibroin and hydrophilic sericin, produced by the silkworm Bombyx mori. In the textile industry, the cocoons of B. mori are processed into silk fabric, where the sericin is substantially removed and usually discarded in wastewater. This wastewater pollutes the environment and water sources. However, sericin has been recognized as a potential biomaterial due to its biocompatibility, immunocompatibility, biodegradability, anti-inflammatory, antibacterial, antioxidant and photoprotective properties. Moreover, sericin can produce hydrogels, films, sponges, foams, dressings, particles, fibers, etc., for various biomedical and pharmaceutical applications (e.g., tissue engineering, wound healing, drug delivery, cosmetics). Given the severe environmental pollution caused by the disposal of sericin and its beneficial properties, there has been growing interest in upcycling this biomaterial, which could have a strong and positive economic, social and environmental impact.

Biomimetic Antibacterial Pro-Osteogenic Cu-Sericin MOFs for Osteomyelitis Treatment

Osteomyelitis is an inflammation of the bone caused by bacterial infection. It usually develops from broken bones, decayed teeth, or heavily punctured wounds. Multi-drug-resistant bacteria are the major hurdle in the treatment of osteomyelitis. The ever-rising antibiotic resistance even leads to amputations or fatalities as a consequence of chronic osteomyelitis. Hence, a single agent with antibacterial activity as well as bone regenerative properties can serve as a potential off-the-shelf product in the treatment of osteomyelitis. Herein, the antibacterial and pro-osteogenic characteristics of copper sericin (Cu-SER) metal-organic frameworks (MOFs) are reported. Sericin, a silk protein with antibacterial activity and an osteoinduction property, acts as an organic template for the deposition of Cu-SER MOFs, similar to collagen during biomineralization in bone. The MOFs exhibit cytocompatibility and osteogenic activity in a dose-dependent manner, as revealed by cell proliferation (alamarBlue) and mineralization (Alizarin Red S and Energy Dispersive X-ray analysis). The bactericidal activity of Cu-SER MOFs was investigated by scanning electron microscopy and a growth kinetic analysis. Together, the report illuminates the unique phenomenon of Cu-SER MOFs that kill bacteria upon contact while being well-tolerated by primary human cells. Hence, Cu-SER MOFs hold the potential to minimize antibiotic dependence.