Retinal-detachment repair and vitreous-like-body reformation via a thermogelling polymer endotamponade.

Internal-tamponade agents are crucial surgical adjuncts in vitreoretinal surgery. Clinically used endotamponade agents act through buoyancy forces, yet can result in prolonged post-operative positioning, temporary loss of vision, raised intra-ocular pressure, cataract formation or the need for additional removal surgery. Here, we describe a thermogelling polymer that provides an internal tamponade effect through surface tension and swelling counter-forces. We tested the long-term biocompatibility of the polymer endotamponade in rabbit vitrectomy models, and its surgical efficacy and biocompatibility in a non-human primate retinal-detachment model. We also show that, while the thermogel biodegrades during the three months following surgery, it promotes the reformation of a vitreous-like body that mimics the biophysical properties of the natural vitreous. The thermogelling endotamponade might serve as a long-term vitreous substitute.

Flexible Modulation of CO-Release Using Various Nuclearity of Metal Carbonyl Clusters on Graphene Oxide for Stroke Remediation.

Utilizing the size-dependent adsorption properties of ruthenium carbonyl clusters (Ru-carbon monoxide (CO)) onto graphene oxide (GO), a facile CO-release platform for in situ vasodilation as a treatment for stroke-related vascular diseases is developed. The rate and amount of formation of the CO-release-active RuII (CO)2 species can be modulated by a simple mixing procedure at room temperature. The subsequent thermally induced oxidation of RuII (CO)2 to RuO2 on the GO surface results in the release of CO. Further modulation of thermal and CO-release properties can be achieved via a hybridization of medium- and high-nuclearity of Ru-CO clusters that produces a RuO2 /RuII (CO)2 /6 Ru-CO-GO composite, where 6 Ru-CO-GO provides a photothermally activated reservoir of RuII (CO)2 species and the combined infrared absorption properties of GO and RuO2 provides photothermal response for in situ CO-release. The RuO2 /RuII (CO)2 /6 Ru-CO-GO composite does not produce any cytotoxicity and the efficacy of the composite is further demonstrated in a cortical photothrombotic ischemia rat model.

A rapid and highly sensitive strain-effect graphene-based bio-sensor for the detection of stroke and cancer bio-markers.

Here, we propose a highly sensitive and rapid bio-sensor for the detection of bio-markers for stroke and cancer-related diseases, based on the utilization of the adsorption properties of ruthenium carbonyl (Ru-CO) clusters on monolayer graphene (MG). A fast rate of decarbonylation of Ru-CO to form ruthenium oxide nanoparticles (RuO2 NPs) on MG was observed. The quantitative detection of matrix metalloproteinase-2 (MMP-2) (bio-marker for stroke and vascular diseases) was demonstrated by tracking the spectral shift of the characteristic G band of graphene caused by the adsorption of RuO2 NPs. A concentration as low as 17 ng mL-1 of MMP-2 was detected in a simulated clinical serum sample. This effective bio-sensor has the potential to revolutionize the biomedical field in the early detection and possible prevention of stroke and cancer diagnosis.

Metal carbonyl-gold nanoparticle conjugates for highly sensitive SERS detection of organophosphorus pesticides.

The binding of organometallic osmium carbonyl clusters onto the surface of gold nanoparticles (10OsCO-Au NPs) greatly enhanced the CO stretching vibration signal at ~2100cm-1, which is relatively free from interference due to the absorbance of biomolecules. By utilizing the acetylcholinesterase (AChE) mediated hydrolysis of acetylthiocholine to thiocholine where the activity of AChE is inhibited by the presence of organophosphate pesticides (OPPs), the subsequent thiocholine-induced aggregation of 10OsCO-Au NPs can be monitored by the change in color of the NPs solution and the variation in intensity of the SERS CO signal. The change in color offers a fast pre-screening method, whereas monitoring via SERS is used for greater accuracy and lower limit of detection (0.1 ppb) for quantitative detection. Its potential as a quick and accurate method of OPPs monitoring in consumer products was demonstrated in the detection of OPPs in real spiked samples such as beer.

Biocompatible electrically conductive nanofibers from inorganic-organic shape memory polymers.

A porous shape memory scaffold with both biomimetic structures and electrical conductivity properties is highly promising for nerve tissue engineering applications. In this study, a new shape memory polyurethane polymer which consists of inorganic polydimethylsiloxane (PDMS) segments with organic poly(ε-caprolactone) (PCL) segments was synthesized. Based on this poly(PCL/PDMS urethane), a series of electrically conductive nanofibers were electrospun by incorporating different amounts of carbon-black. Our results showed that after adding carbon black into nanofibers, the fiber diameters increased from 399±76 to 619±138nm, the crystallinity decreased from 33 to 25% and the resistivity reduced from 3.6 GΩ/mm to 1.8 kΩ/mm. Carbon black did not significantly influence the shape memory properties of the resulting nanofibers, and all the composite nanofibers exhibited decent shape recovery ratios of >90% and shape fixity ratios of >82% even after 5 thermo-mechanical cycles. PC12 cells were cultured on the shape memory nanofibers and the composite scaffolds showed good biocompatibility by promoting cell-cell interactions. Our study demonstrated that the poly(PCL/PDMS urethane)/carbon-black nanofibers with shape memory properties could be potentially used as smart 4-dimensional (4D) scaffolds for nerve tissue regeneration.

Thermally Stable and Sterilizable Polymer Transistors for Reusable Medical Devices.

We realize a thermally stable polymer thin film transistor (TFT) that is able to endure the standard autoclave sterilization for reusable medical devices. A thermally stable semiconducting polymer poly[4-(4,4-dihexadecyl-4Hcyclopenta[1,2-b:5,4-b]dithiophen-2-yl)-alt[1,2,5]thiadiazolo [3,4c] pyridine], which is stable up to 350 °C in N2 and 200 °C in air, is used as channel layer, whereas the biocompatible SU-8 polymer is used as a flexible dielectric layer, in addition to conventional SiO2 dielectric layer. Encapsulating with in-house designed composite film laminates as moisture barrier, both TFTs using either SiO2 or SU-8 dielectric layer exhibit good stability in sterilized conditions without significant change in mobility and threshold voltage. After sterilization for 30 min in autoclave, the mobility drops only 15%; from as-fabricated mobility of 1.4 and 1.3 cm(2) V(-1) s(-1) to 1.2 and 1.1 cm(2) V(-1) s(-1) for TFTs with SiO2 and SU-8 dielectric layer, respectively. Our TFT design along with experimental results reveal the opportunity on organic/polymer flexible TFTs in sterilizable/reusable medical device application.

Recent Progress in Using Biomaterials as Vitreous Substitutes.

Vitreous substitutes are crucial adjuncts during vitreo-retinal surgery for retinal diseases such as complicated retinal detachment, macular holes, complications of diabetic retinopathy, and ocular trauma involving posterior segment. In retinal detachment surgery, an internal tamponade agent is required to provide internal pressure for reattachment of the detached neurosensory retina. Current available options serve only as a temporary surgical adduct or short-term solution and are associated with inherent problems. Despite many years of intensive research, an ideal vitreous substitute remains elusive. Indeed, the development of an ideal vitreous substitute requires the concerted efforts of synthetic chemists and biomaterial engineers, as well as ophthalmic surgeons. In this review, we propose that polymeric hydrogels present the future of artificial vitreous substitutes due to its high water composition, optical transparency, and rheological properties that closely mimic the natural vitreous. In particular, thermosensitive smart hydrogels, with reversible sol to gel change, have emerged as the material class with the most potential to succeed as ideal vitreous substitutes, facilitating easy implementation during surgery. Importantly, these smart hydrogels also display potential as efficacious drug delivery systems.

Enhanced performance using an SU-8 dielectric interlayer in a bulk heterojunction organic solar cell.

The effect of inserting an SU-8 dielectric interlayer into inverted bulk heterojunction (BHJ) organic solar cells (OSCs) was studied. Insertion of an ultrathin layer of SU-8 between the zinc oxide (ZnO) electron transport layer and the photoactive layer resulted in a smoother interface and a 14% enhancement in power conversion efficiency. The properties of devices with and without an SU-8 interlayer were investigated using transient photovoltage (TPV) and double injection (DoI) techniques, and it was found that devices with SU-8 show longer carrier lifetimes and greater mobility-lifetime (µ-τ) products than those without. Devices with SU-8 were also found to have improved stability. The results indicate that the insertion of an SU-8 interlayer reduces the recombination rate for photogenerated carriers without affecting the charge transport properties, improving overall performance and stability.

Nanoparticle-Hydrogel Composites: Concept, Design, and Applications of These Promising, Multi-Functional Materials.

New technologies rely on the development of new materials, and these may simply be the innovative combination of known components. The structural combination of a polymer hydrogel network with a nanoparticle (metals, non-metals, metal oxides, and polymeric moieties) holds the promise of providing superior functionality to the composite material with applications in diverse fields, including catalysis, electronics, bio-sensing, drug delivery, nano-medicine, and environmental remediation. This mixing may result in a synergistic property enhancement of each component: for example, the mechanical strength of the hydrogel and concomitantly decrease aggregation of the nanoparticles. These mutual benefits and the associated potential applications have seen a surge of interest in the past decade from multi-disciplinary research groups. Recent advances in nanoparticle-hydrogel composites are herein reviewed with a focus on their synthesis, design, potential applications, and the inherent challenges accompanying these exciting materials.

Air-stable efficient inverted polymer solar cells using solution-processed nanocrystalline ZnO interfacial layer.

In this work, efficient bulk heterojunction (BHJ) organic solar cells (OSC) in inverted configuration have been demonstrated. Power conversion efficiency (PCE) of 3.7% is reported for OSC employing silver top electrodes, molybdenum trioxide (MoO3) as the hole-transport interlayer (HTL), active layer comprising of poly-3-hexylthiophene (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) as well as a nanocrystalline solution-synthesized zinc oxide (ZnO) nanoparticle (NP) film as the electron-transport layer (ETL). By using solution-processable ZnO crystalline NPs as ETL, we can eliminate the typical high temperature processing/annealing step, which is widely adopted in the conventional ZnO ETL fabrication process via the sol-gel method. Such highly crystalline ZnO NP films can enhance charge collection at the electrodes. It is also found that inverted OSCs exhibit greater air stability and lifetime performance compared to the OSC employing the normal structure.

Charge mobility and recombination in a new hole transporting polymer and its photovoltaic blend.

The charge mobility in a new hole transporting polymer, poly(2,6-bis(thiophene-2-yl)-3,5-dipentadecyldithieno[3,2-b;2',3'-d]thiophene) (PBTDTT-15), and its blend with (6,6)-phenyl-C(70)-butyric acid methyl ester (PC(70)BM) in a weight ratio of 1:3 at ambient atmosphere condition was investigated using time-of-flight (TOF) photoconductivity and photoinduced charge extraction by linearly increasing voltage (PhotoCELIV) techniques. The bulk heterojunction based photovoltaic (PV) blend (PBTDTT-15:PC(70)BM (1:3)) exhibited a promising power conversion efficiency (PCE) of 3.23% under air mass 1.5 global (AM 1.5G) illumination of 100mW/cm(2). The charge mobility and recombination properties of the best performing cells were investigated. The hole mobility in the pure PBTDTT-15 was in the range of 4 x 10(-4) cm(2)/(V s), which was reduced almost 5 times in the PBTDTT-15:PC(70)BM (1:3) blend. The PhotoCELIV transient observed for the photovoltaic (PV) blend was dominated by electrons, with the charge mobility of the order of 10(-3) cm(2)/(V s), and a weak shoulder at a long time scale due to holes. The effective bimolecular recombination coefficient (beta) obtained for the PV blend deviated significantly from the Langevin recombination coefficient (beta(L)) indicating a phase-separated morphology. The obtained results indicate that the PBTDTT-15:PC(70)BM blend can be potential for organic solar cell applications.