Fabrication of free-standing nanoparticle-fused nanosheets and their hetero-modification using sacrificial film

Emerging Applications of Nanotechnology in Healthcare Systems: Grand Challenges and Perspectives

Healthcare, as a basic human right, has often become the focus of the development of innovative technologies. Technological progress has significantly contributed to the provision of high-quality, on-time, acceptable, and affordable healthcare. Advancements in nanoscience have led to the emergence of a new generation of nanostructures. Each of them has a unique set of properties that account for their astonishing applications. Since its inception, nanotechnology has continuously affected healthcare and has exerted a tremendous influence on its transformation, contributing to better outcomes. In the last two decades, the world has seen nanotechnology taking steps towards its omnipresence and the process has been accelerated by extensive research in various healthcare sectors. The inclusion of nanotechnology and its allied nanocarriers/nanosystems in medicine is known as nanomedicine, a field that has brought about numerous benefits in disease prevention, diagnosis, and treatment. Various nanosystems have been found to be better candidates for theranostic purposes, in contrast to conventional ones. This review paper will shed light on medically significant nanosystems, as well as their applications and limitations in areas such as gene therapy, targeted drug delivery, and in the treatment of cancer and various genetic diseases. Although nanotechnology holds immense potential, it is yet to be exploited. More efforts need to be directed to overcome these limitations and make full use of its potential in order to revolutionize the healthcare sector in near future.

Adhesive and robust multilayered poly(lactic acid) nanosheets for hemostatic dressing in liver injury model

Freestanding biodegradable nanosheets composed of poly(l-lactic acid) (PLLA) have been developed for various biomedical applications. These nanosheets exhibit unique properties such as high adhesiveness and exquisite flexibility; however, they burst easily due to their nanometer thickness. We herein describe a freestanding, multilayered nanosheet composed of PLLA fabricated using a simple combination procedure: (i) multilayering of PLLA and alginate, (ii) gelation of the alginate layers, (iii) fusion-cut sealing, and (iv) elution of the alginate layers. The multilayered nanosheets not only reinforced the bursting strength but also provided a high level of adhesive strength. In fact, they were found to show potential as a hemostatic dressing, and they tended to show reduced tissue adhesion that accompanies liver injury. Therefore, we propose this biomaterial as a candidate for an alternative to conventional therapy in hemorrhage. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1747-1757, 2017.

Poly(ɛ-caprolactone) (PCL)-polymeric micelle hybrid sheets for the incorporation and release of hydrophilic proteins

Sheets have several advantages over conventional gel- or particle-type drug carriers. Sheets have several notable attributes: sheets' size and shape are easily adjustable, sheets are highly accessible in surgery, and sheets have a large contact area relative to drug-targeting sites. However, it is difficult to incorporate hydrophilic proteins into hydrophobic sheets and to release the proteins over the long term in a sustained manner. In the present study, we show that "poly(ɛ-caprolactone) (PCL)-polymeric micelle hybrid sheets" can be used for the incorporation and release of hydrophilic proteins. Polymeric micelles (i.e., spaces that can incorporate hydrophilic compounds) are, in this study, uniformly dispersed in hydrophobic and biocompatible biomaterial sheet. We have clarified that the composition of block copolymer, methoxy-terminated poly(ethylene glycol)-block-poly(ɛ-caprolactone) (CH3O-PEG-b-PCL), can affect two variables: the stability of w/o emulsion and the release properties of the resulting sheets, by means of visual qualitative observations, newly developed quantitative analyses (advanced fractal analysis, advanced FD) based on deviation of the fractal dimension (FD), and release experiments. We clarified that the release behavior of BSA was affected by the composition of the block copolymers and the resulting emulsion. The results obtained in this paper show that the hydrophobic sheets in which polymeric micelles providing hydrophilic spaces were dispersed could be an effective platform for incorporating and releasing hydrophilic proteins.

Asymmetric free-standing film with multifunctional anti-bacterial and self-cleaning properties

A superhydrophobic/hydrophilic asymmetric free-standing film has been created using layer-by-layer assembly technique. Poly(ethylene-imine)-Ag(+) complex (PEI-Ag(+)) at pH 9.0 was assembled with poly(acrylic acid) (PAA) at pH 3.2 on a Teflon substrate to yield a micronanostructured surface that can be turned to be superhydrophobic after being coated with a low surface energy compound. Silver nanoparticle loaded free-standing film with one surface being superhydrophobic while the other surface is hydrophilic was then obtained after detachment from the substrate. The superhydrophobicity enabled the upper surface with anti-adhesion and self-cleaning properties and the hydrophilic bottom surface can release silver ions as antibiotic agent. The broad-spectrum antimicrobial capability of silver ions released from the bottom surface coupled with superhydrophobic barrier protection of the upper surface may make the free-standing film a new therapy for open wound.

Strain patterning and direct measurement of Poisson's ratio in nanoparticle monolayer sheets

Close-packed monolayers self-assembled from ligated nanoparticles can form 10 nm thin sheets that stretch over micrometer-wide holes. Employing electron and focused ion beams, we show that one can locally tailor the strain in such sheets while they remain clamped around their perimeter, making it possible to imprint strain fields by design. Furthermore, using the nanoparticles themselves to track imposed strain gradients allows for the first direct measurement of Poisson's ratio in these two-dimensional materials.

Magnetic Nanofilms for Biomedical Applications

Polymeric ultrathin films, also called nanofilms or nanosheets, show peculiar properties making them potentially useful for several applications in biomedicine, e.g., as nanoplasters for localized drug release or as a new solution for closing endoluminal surgical wounds. In this sense, one of most challenging issues is film control in the working environment: the possibility of including magnetic components, such as magnetic nanoparticles or nanotubes, paves the way for the effective use of nanofilms in the human body, by allowing precise positioning by an external magnetic field. State of the art and new perspectives of magnetic nanofilms for biomedical applications are here presented, including fabrication, modeling, characterization and validation.

Novel platelet substitutes: disk-shaped biodegradable nanosheets and their enhanced effects on platelet aggregation

We have studied biocompatible spherical carriers carrying a dodecapeptide, HHLGGAKQAGDV (H12), on their surface as platelet substitutes. This peptide is a fibrinogen γ-chain carboxy-terminal sequence (γ400-411) and specifically recognizes the active form of glycoprotein IIb/IIIa on activated platelets. Our purpose is to assess the possibility of making a novel platelet substitute consisting of disk-shaped nanosheets having a large contact area for the targeting site, rather than conventional small contact area spherical carriers. The H12 peptide was conjugated to the surface of the free-standing nanosheets made of biodegradable poly(d,l-lactide-co-glycolide) (PLGA). These H12-PLGA nanosheets were fabricated onto 3 μm disk-shaped patterned hydrophobic octadecyl regions on a SiO(2) substrate. By way of comparison, spherical H12-PLGA microparticles with the same surface area and conjugation number of H12 were also prepared. The resulting H12-PLGA nanosheets specifically interacted with the activated platelets adhered on the collagen surface at twice the rate of the H12-PLGA microparticles under flow conditions, and showed platelet thrombus formation in a two-dimensional spreading manner. Thus, H12-PLGA nanosheets might be a suitable candidate novel platelet alternative substitute for infused human platelet concentrates for the treatment of bleeding in patients with severe thrombocytopenia.

Development of biodegradable nanosheets as nanoadhesive plaster

Sheet-shaped carriers having both obverse and reverse surfaces (thus, a large contact area for targeting a site and adhesive properties without any chemical cross-linker onto tissue surface) have several advantages as surgical dressings. These advantages include active targeting over spherically shaped carriers, which thus have an extremely small contact area for targeting sites. Here, we propose a novel methodology for preparation of a free-standing, ultra-thin, and biocompatible polymer nanosheet having heterosurfaces, fabricated through macromolecular assembly. In the context of biomedical applications, the targeted properties include injectable sheet-shaped drug carriers having precisely controlled size by exploiting micropatterned substrate, and giant polymer nanosheets composed of biocompatible polysaccharides. A huge aspect ratio, in excess of 106, is particularly applicable for novel surgical dressings. These biocompatible polymer nanosheets having heterosurfaces can thus be regarded as new biomaterials for minimally invasive treatment.