Development of a ubiquitously transferrable silver-nanoparticle-loaded polymer nanosheet as an antimicrobial coating.

Ultra-thin polymer films (nanosheets) fabricated by a layer-by-layer (LbL) method possess unique properties such as high flexibility, adhesive strength, and transparency, and can be peeled off from a substrate and attached to various surfaces via a water-soluble supporting film. Therefore, flexible and transferrable LbL nanosheets are convenient tools as coating materials. Here, we fabricated a novel antimicrobial coating material by embedding silver nanoparticles (AgNPs) in an LbL nanosheet composed of layers of chitosan and sodium alginate (Ag-LbL nanosheet) by means of a photo-reduction method. Optimizing the amount of irradiated energy applied led to robust antimicrobial efficacy against methicillin-resistant Staphylococcus aureus (MRSA), sufficient to meet ISO standards (ISO 22196), while maintaining the flexibility and adhesive potency of the LbL nanosheet. Thus, the Ag-LbL nanosheet is a promising coating material that can provide antimicrobial efficacy to various surfaces.

Sustainable antimicrobial effect of silver sulfadiazine-loaded nanosheets on infection in a mouse model of partial-thickness burn injury.

Partial-thickness burn injury has the potential for reepithelialization and heals within 3weeks. If the wound is infected by bacteria before reepithelization, however, the depth of disruption increases and the lesion easily progresses to the full-thickness dermal layers. In the treatment of partial-thickness burn injury, it is important to prevent the wound area from bacterial infection with an antimicrobial dressing. Here, we have tested the antimicrobial properties of polymeric ultra-thin films composed of poly(lactic acid) (termed "PLA nanosheets"), which have high flexibility, adhesive strength and transparency, and silver sulfadiazine (AgSD), which exhibits antimicrobial efficacy. The AgSD-loaded nanosheet released Ag(+) for more than 3days, and exerted antimicrobial efficacy against methicillin-resistant Staphylococcus aureus (MRSA) in an in vitro Kirby-Bauer test. By contrast, a cell viability assay indicated that the dose of AgSD used in the PLA nanosheets did not show significant cytotoxicity toward fibroblasts. In vivo evaluation using a mouse model of infection in a partial-thickness burn wound demonstrated that the nanosheet significantly reduced the number of MRSA bacteria on the lesion (more than 10(5)-fold) and suppressed the inflammatory reaction, thereby preventing a protracted wound healing process.

Development of latanoprost-loaded biodegradable nanosheet as a new drug delivery system for glaucoma.

PURPOSE: We investigated the IOP reduction and safety of latanoprost-loaded biodegradable nanosheet (LBNS) as a new antiglaucoma drug delivery system (DDS). METHODS: We fabricated a 40 nm thick multilayered biodegradable nanosheet that is composed of chitosan and sodium alginate by means of the layer-by-layer method. Latanoprost isopropyl ester was loaded on the nanosheet to prepare 25, 2.5, and 0.25 µg/cm(2) LBNSs. A nanosheet without latanoprost isopropyl ester (NS) and 0.005% latanoprost ophthalmic solution were prepared as controls. LBNSs or NS was applied to rat cornea, and IOP was monitored for 9 days. Local adverse effects and eye scratching movement also were investigated. The amount of latanoprost acid in aqueous humor and was measured in rabbits. RESULTS: The 0.25 µg/cm(2) LBNS and 0.005% latanoprost ophthalmic solution showed significant IOP reduction only for 1 day after application, whereas the IOP reduction rates of 2.5 µg/cm(2) LBNS at 1, 2, 4, 7, and 9 days after application were -27.0% ± 14.8%, -22.0% ± 16.7%, -25.8% ± 18.0%, -22.7% ± 20.9%, and -6.6% ± 17.0%, respectively. The 25 µg/cm(2) LBNS reduced IOP in a similar manner. The 25 µg/cm(2) LBNS induced transient hyperemia, whereas the 0.25 and 2.5 µg/cm(2) LBNSs did not exert any local adverse effects. The eye scratching movement test showed that application of 25 µg/cm(2) LBNS did not cause any irritation of the eye. Latanoprost acid was detected in aqueous humor up to 6 days after application of 2.5 µg/cm(2) LBNS. CONCLUSIONS: LBNS may be used as a novel antiglaucoma DDS.

Fragmentation of poly(lactic acid) nanosheets and patchwork treatment for burn wounds.

Freestanding poly(L-lactic acid) (PLLA) nanosheets are mass-produced by a simple combination of a spin-coating-assisted multi-layering process and a peeling technique. The resulting PLLA nanosheets are fragmented by homogenization and then reconstructed into a "patchwork" sheet on various surfaces without any adhesive reagents. The patchwork is shown to offer excellent protection against burn wound infection with Pseudomonas aeruginosa, and may therefore be an alternative to conventional burn therapy for prevention of infection.

Therapeutic efficacy of an antibiotic-loaded nanosheet in a murine burn-wound infection model.

Polymeric ultra-thin films (nanosheets) possess unique properties that make them suitable materials for various biomedical applications. In our previous study, we assessed the use of an antibiotic (tetracycline, TC)-loaded nanosheet (or "TC-nanosheet") for the treatment of gastrointestinal tissue defects. The nanosheet consisted of three functional layers: layer-by-layer nanosheet as a stable platform, TC as an antimicrobial agent with autofluorescence for tracing, and a poly(vinyl acetate) nanosheet to act as a protecting layer. The TC-nanosheet has high flexibility, adhesive strength and transparency. Here, we evaluated the effectiveness of the TC-nanosheet in preventing full thickness burn-wound infections. In an in vivo study, murine dorsal skin was injured by full-thickness burns and then infected with Pseudomonas aeruginosa (P. aeruginosa), a common bacterium causing burn-associated infections. The wound site was treated either with a TC-nanosheet, TC-unloaded nanosheet or left untreated. Wound management was facilitated by the high transparency of the TC-nanosheet. The TC-nanosheet significantly improved burn-wound infection by P. aeruginosa in mice. Indeed, all mice treated with the TC-nanosheet survived, whereas the other treatment groups displayed increased rates of mortality due to bacterial infection. According to histological analyses and viable bacterial counting in the liver (bacterial translocation), the TC-nanosheets were able to prevent not only the local inflammation but also systemic inflammation. We conclude that the TC-nanosheet can act as an effective treatment for full-thickness burn-wound infection. Hence, the TC-nanosheet is a promising therapeutic tool for burn-wound management in severely burn-injured patients.

Dual therapeutic action of antibiotic-loaded nanosheets for the treatment of gastrointestinal tissue defects.

An ultra-thin polymer film (nanosheet) composed of polysaccharides (i.e., polysaccharide nanosheet) provides sufficient adhesiveness, flexibility and robustness to act as an effective wound dressing. We have recently demonstrated the sealing effect of a nanosheet on a murine cecal puncture. Nevertheless, a small percentage of bacteria penetrated the nanosheet because of its ultra-thin structure. Here, we have developed an antibiotic-loaded nanosheet to inhibit bacterial penetration and investigated its therapeutic efficacy using a model of a murine cecal puncture. Tetracycline (TC) was sandwiched between a poly(vinylacetate) (PVAc) layer and the polysaccharide nanosheet (named PVAc-TC-nanosheet). Under physiological conditions, TC was released from the nanosheet for 6 h. Microscopic observation between the interface of the PVAc-TC-nanosheet and bacteria demonstrated how its potent anti-microbial effect was achieved. In vivo studies show that overlapping therapy with the PVAc-TC-nanosheet (thickness: 177 nm) significantly increases mouse survival rate after cecal puncture as well as suppressing an increase in the intraperitoneal bacterial count and leukocyte count.

Development of blood vessel viewer using multi spectral imaging technology.

Using multi spectral imaging technology, which enable us to simultaneously obtain spatial and wavelength information, we have newly developed blood vessel viewer. Our device is composed of the light source, the lens or the endoscope, the optical device, CCD camera, and PC. As an evaluation of our device, we measured the skin diffuse reflectance spectrum of the human hand. The blood vessel observed by our device was corresponding to an anatomy finding. However, even if Principal Component Analysis was used, the reflection of horny was not able to be removed completely.