Design of an injectable in situ gelation biomaterials for vitreous substitute.

To adapt the physical properties of living materials to their biological function, nature developed various types of polymers with outstanding physical behavior. One example is the vitreous body, which is important intraocular elements not only because of its optical and mechanical performances, but also due to its important role in the pathogenesis and treatment of conditions affecting adjacent tissues and eventually the whole eye. Here, we report a novel biocompatible material for injectable vitreous substitute, composed of thermosensitive amphiphilic polymer, which is capable of forming a transparent gel in the vitreous cavity. It is nontoxic, provides adequate support for the retina, and allows light to reach the sensory elements at the back of the eye. The amphiphilic polymer exhibits mechanical stability by assembling to form highly interconnected hydrophobic domains, which leads to the constitution of a network structure.

UV patterned nanoporous solid-liquid core waveguides.

Nanoporous Solid-Liquid core waveguides were prepared by UV induced surface modification of hydrophobic nanoporous polymers. With this method, the index contrast (deltan = 0.20) is a result of selective water infiltration. The waveguide core is defined by UV light, rendering the exposed part of a nanoporous polymer block hydrophilic. A propagation loss of 0.62 dB/mm and a bend loss of 0.81 dB/90 degrees for bend radius as low as 1.75 mm was obtained in these multimode waveguides.

Physisorption of SDS in a hydrocarbon nanoporous polymer.

Surface modification of nanoporous 1,2-polybutadiene of pore diameter approximately 15 nm was accomplished by physisorption of sodium dodecyl sulfate (SDS) in water. Loading of the aqueous solution and the accompanying physisorption of SDS into the hydrophobic nanoporous films were investigated in a wide range of concentrations. The loading showed varying dependence on the SDS concentration. No loading was observed for SDS concentrations below 4.0 mM. At concentrations above 5.0 mM, the initial part of loading showed a linear dependence on the square root of time, which can be interpreted as diffusion-controlled dynamics. Both the specific equilibrium loading and the final SDS adsorption reached plateau values at concentrations above 6.8 mM. The infiltration of SDS into the nanoporous film was mainly followed by gravimetry and for a few samples confirmed by X-ray photoelectron spectroscopy (XPS). The SDS adsorption isotherm can be well described by the Langmuir model, consistent with a monolayer adsorption onto the pore walls. The surface modified by the surfactant clearly showed water wettability, in contrast to the original hydrophobic nanoporous 1,2-PB. We also looked at the release process of SDS out of the nanopores in the presence of excess of water or methanol. A discussion of the very different time scales of release in the two media is presented at the end of the paper.

Surface modification of nanoporous 1,2-polybutadiene by atom transfer radical polymerization or click chemistry.

Surface-initiated atom transfer radical polymerization (ATRP) and click chemistry were used to obtain functional nanoporous polymers based on nanoporous 1,2-polybutadiene (PB) with gyroid morphology. The ATRP monolith initiator was prepared by immobilizing bromoester initiators onto the pore walls through two different methodologies: (1) three-step chemical conversion of double bonds of PB into bromoisobutyrate, and (2) photochemical functionalization of PB with bromoisobutyrate groups. Azide functional groups were attached onto the pore walls before click reaction with alkynated MPEG. Following ATRP-grafting of hydrophilic polyacrylates and click of MPEG, the originally hydrophobic samples transformed into hydrophilic nanoporous materials. The successful modification was confirmed by infrared spectroscopy, contact angle measurements and measurements of spontaneous water uptake, while the morphology was investigated by small-angle X-ray scattering and transmission electron microscopy.

Structural evolution of human recombinant alpha B-crystallin under UV irradiation.

External stresses cause certain proteins to lose their regular structure and aggregate. In order to clarify this abnormal aggregation process, a structural evolution of human recombinant alphaB-crystallin under UV irradiation was observed with in situ small-angle neutron scattering. The abnormal aggregation process was identified to fall in three time zones: incubation, aggregation, and saturation. During the incubation time, the size of aggregates was almost unchanged but a deformation in the local structure was developing. After the incubation time, abnormal aggregation proceed. When the volume of the aggregates reached around twice the size as that of the initial aggregates, the aggregation rate slowed down, which marked the onset of saturation.

Nanoporous materials with spherical and gyroid cavities created by quantitative etching of polydimethylsiloxane in polystyrene-polydimethylsiloxane block copolymers.

A new method for quantitative etching of the poly(dimethylsiloxane) block in polystyrene-poly(dimethylsiloxane) (PS-PDMS) block copolymers is reported. Reacting the block copolymer with anhydrous hydrogen fluoride renders a nanoporous material (NPM) with the remaining glassy PS maintaining the original bulk morphology. 1H NMR, mass difference, size exclusion chromatography, and X-ray photoelectron spectroscopy were used to characterize the materials before and after etching. NPMs containing spherical and gyroid cavities were prepared, as ascertained by small-angle X-ray scattering. This is the first report on block copolymer-based NPM films of millimeter thickness containing secluded spherical holes. Surface images by AFM and SEM are consistent with the SAXS findings.