Shinya Ohtsubo

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 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.

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.

Application of decorrelation stretching method to hyperspectral fundus image processing

We have developed a near-infrared hyperspectral imaging system that can acquire both spectral and spatial data covering a 50-degree field at the fundus surface within 5 seconds. Single wavelength band reflectance images with bandwidth of 20 nm have demonstrated that choroidal vascular patterns can be clearly observed as bright images for the central wavelength ranging from 740 to 860 nm, while retinal blood vessels are seen as dark images for that ranging from 740 to 920 nm. It is desirable for clinical use to separate the choroidal vascular patterns image from the retinal blood vessels image. To this end, we have applied the decorrelation stretch to processing of spectral images. We have found the following. Original fundus spectral images have stripes noise. The decorrelation stretch emphasizes the noise and, thus, the noise has to be removed by, for example, DCT (Discrete Cosine Transform) filter beforehand. The choroidal vascular image can be successfully separated from the retinal vascular image. Furthermore, the macular is superimposed on the latter as it should be so from the viewpoint of anatomy. The result suggests that useful information may be extracted by combining hyperspectral images with the decorrelation stretch.

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.