Rungnapha Yamdech

The safety and efficacy of bacterial nanocellulose wound dressing incorporating sericin and polyhexamethylene biguanide: in vitro, in vivo and clinical studies

In our previous work, we have attempted to develop a novel bacterial nanocellulose wound dressing which composed of both polyhexamethylene biguanide (PHMB) as an antimicrobial agent and sericin as an accelerative wound healing component. The loading sequence and concentration of PHMB and sericin were optimized to provide the wound dressing with the most effective antimicrobial activity and enhanced collagen production. In this study, further in vitro, in vivo, and clinical studies of this novel wound dressing were performed to evaluate its safety, efficacy, and applicability. For the in vitro cytotoxic test with L929 mouse fibroblast cells, our novel dressing was not toxic to the cells and also promoted cell migration as good as the commercially available dressing, possibly due to the component of sericin released. When implanted subcutaneously in rats, the lower inflammation response was observed for the novel dressing implanted, comparing to the commercially available dressing. This might be that the antimicrobial PHMB component of the novel dressing played a role to reduce infection and inflammation reaction. The clinical trial patch test was performed on the normal skin of healthy volunteers to evaluate the irritation effect of the dressing. Our novel dressing did not irritate the skin of any volunteers, as characterized by the normal levels of erythema and melanin and the absence of edema, papule, vesicle, and bullae. Then, the novel dressing was applied for the treatment of full-thickness wounds in rats. The wounds treated with our novel dressing showed significantly lower percentage of wound size and higher extent of collagen formation mainly due to the activity of sericin. We concluded that our novel bacterial nanocellulose incorporating PHMB and sericin was a safe and efficient wound dressing material for further investigation in the wound healing efficacy in clinic.

Physical and biological assessments of the innovative bilayered wound dressing made of silk and gelatin for clinical applications

The physical and biological assessments of the innovative bilayered wound dressing made of silk and gelatin that we have developed previously were performed to evaluate its efficacy for clinical applications. The absorption ability and dehydration rate of the dressing were assessed using the split-thickness skin graft and leg ulcer wound bed models. The bioactivities of the bilayered wound dressing were evaluated. The bilayered dressing showed continuous absorption rate of wound exudate, providing the suitability for the wound with extended inflammation phase. The dehydration rate of the bilayered dressing was comparable to the commercially available dressing of which the moisture maintenance capability is claimed. The bilayered dressing showed good conformability, as can be seen by the homogeneous distribution pattern of bromophenol blue absorbed. In terms of biological activities, the bilayered dressing was less toxic to skin cells than the commercially available dressing. The bilayered dressing was also shown to promote cell migration and collagen production due to the bioactive protein components. We here concluded that the superior properties of the bilayered dressing over the commercially available dressing were the conformability and biological activities to accelerate the wound healing, while the other properties were comparable to those of commercially available dressing. The data obtained in this study would be very useful for the further evaluation of the bilayered dressing in clinical trial.

Stability enhancement of mulberry-extracted anthocyanin using alginate/chitosan microencapsulation for food supplement application

Abstract The stability of mulberry-extracted anthocyanin is a main concern in food supplement application. In this article, the alginate/chitosan beads were fabricated by spray drying and external gelation techniques using different processes: (1) dropping a sodium alginate solution into a CaCl2 solution containing chitosan and (2) incubating calcium alginate beads in a solution of chitosan. These beads were introduced as microcarrier to enhance the stability and bioavailability of anthocyanin. We showed that the beads fabricated by different processes could encapsulate the anthocyanin at different amounts. All alginate/chitosan beads had high swelling percentage under pH 6 and 7.4 but not completely swell at pH 1 and 4. The alginate/chitosan beads degraded in a simulated gastric fluid condition (SGF) in the faster rate than that in a simulated intestinal fluid condition (SIF). Under SGF condition, the release of anthocyanin seemed to be governed by electrostatic interaction while the release of anthocyanin under SIF condition may be manipulated by the beads’ degradation. Herein, we showed that the beads produced by incubating calcium alginate beads in 0.05% chitosan solution were the most appropriate microcarriers for encapsulation of mulberry-extracted anthocyanin which showed high encapsulation efficiency and had resistance to gastric condition.

Controlled Release of Chitosan and Sericin from the Microspheres-Embedded Wound Dressing for the Prolonged Anti-microbial and Wound Healing Efficacy

ABSTRACTOne approach in wound dressing development is to incorporate active molecules or drugs in the dressing. In order to reduce the frequency of dressing changes as well as to prolong wound healing efficacy, wound dressings that can sustain the release of the active molecules should be developed. In our previous work, we developed chitosan/sericin (CH/SS) microspheres that released sericin in a controlled rate. However, the difficulty of applying the microspheres that easily diffuse and quickly degrade onto the wound was its limitations. In this study, we aimed to develop wound dressing materials which are easier to apply and to provide extended release of sericin. Different amounts of CH/SS microspheres were embedded into various compositions of polyvinyl alcohol/gelatin (PVA/G) scaffolds and fabricated using freeze-drying and glutaraldehyde crosslinking techniques. The obtained CH/SS microspheres-embedded scaffolds with appropriate design and formulation were introduced as a wound dressing material. Sericin was released from the microspheres and the scaffolds in a sustained manner. Furthermore, an optimized formation of the microspheres-embedded scaffolds (2PVA2G+2CHSS) was shown to possess an effective antimicrobial activity against both gram-positive and gram-negative bacteria. These microspheres-embedded scaffolds were not toxic to L929 mouse fibroblast cells, and they did not irritate the tissue when applied to the wound. Finally, probably by the sustained release of sericin, these microspheres-embedded scaffolds could promote wound healing as well as or slightly better than a clinically used wound dressing (Allevyn®) in a mouse model. The antimicrobial CH/SS microspheres-embedded PVA/G scaffolds with sustained release of sericin would appear to be a promising candidate for wound dressing application.

Development of bacterial cellulose incorporating silk sericin, polyhexamethylene biguanide, and glycerin with enhanced physical properties and antibacterial activities for wound dressing application

ABSTRACT Bacterial cellulose (BC) has been applied for wound dressing application. In this study, physical and biological properties of the BC dressing were improved by incorporation of silk sericin (SS), polyhexamethylene biguanide (PHMB), and glycerin. The glycerin incorporation reduced dehydration rate and wound adhesion of the BC dressing in a concentration-dependent manner. PHMB, an antiseptic agent, provided antibacterial activity against Gram-positive and Gram-negative bacteria. Meanwhile, SS would enhance collagen and tissue formation in wounds. Finally, we confirmed that the BC dressing incorporating SS, PHMB, and glycerin was safe to be used as a medical material according to ISO 10993-6 standard. GRAPHICAL ABSTRACT

Stability of Anthocyanin from Mulberry Extracts in Alginate Microspheres at High Temperature

The aim of this study was to investigate stabilities of anthocyanins from mulberry fruits extracts in alginate microspheres. The total anthocyanins contents measured from water extracts of mulberry fruits (Chiangmai/Jul cultivars) were at 10.46±0.51 mg/g DW and 15.31±0.86 mg/g DW (Chiangmai/Korat cultivars). At high temperature the extracts lost their anthocyanin contents to 52%wt (at 100°C for 5 hour) and 73%wt (at 121°C for 20 min). Alginate microspheres were prepared using external gelation methods. Sodium alginate solution (2.5%w/v) was sprayed into CaCl2 solution (0.1M) through a nozzle at N2 flow rates of 20 L/min. The average bead sizes were at 342.03±3.21µm. Anthocyanins loading on alginate microspheres were at 2.283±0.15 mg/g dry weight. At 80(10h), 100(5h) and 121°C(20min), Anthocyanins retention were at 91%wt, 82%wt and 89%wt, respectively. Adsorption of anthocyanins from mulberry fruit extracts on alginate microspheres resulted in a greater stability at high temperature than that of the free anthocyanins.