No abstract

In this study, an injectable, photocurable gelatin system, consisting of acrylated gelatin and thiolated gelatin, with tunable mechanical, biodegradation, and biological properties was used as a potential cell-supportive scaffold for the repair of focal corneal wounds. The mechanical property of hydrogels can be readily modified (postcure shear modulus of between 0.3 and 22 kPa) by varying the ratio of acrylate to thiol groups, photointensity, and solid content, and the biodegradation times also varied with the change of solid content. More importantly, the generated hydrogels exhibited excellent cell viability in both cell seeding and cell encapsulation experiments. Furthermore, the hydrogels were found to be biocompatible with rabbit cornea and aided the regeneration of a new tissue under a focal corneal wound (exhibiting epithelial wound coverage in <3d), and ultraviolet irradiation did not have any obvious harmful effect on the cornea and posterior eye segment tissues. Along with their injectability and tunable mechanical properties, the photocurable thiol-acrylate hydrogels showed promise as corneal substitutes or substrates to construct a new corneal tissue.

We describe novel lyotropic liquid-crystalline (LLC) materials based on photoresponsive amphiphiles that exhibit rapid photoswitchable rheological properties of unprecedented magnitude between solidlike and liquidlike states. This was achieved through the synthesis of a novel azobenzene-containing surfactant (azo-surfactant) that actuates the transition between different LLC forms depending on illumination conditions. Initially, the azo-surfactant/water mixtures formed highly ordered and viscous LLC phases at 20-55 wt % water content. Spectroscopic, microscopic, and rheological analysis confirmed that UV irradiation induced the trans to cis isomerization of the azo-surfactant, leading to the disruption of the ordered LLC phases and a dramatic, rapid decrease in the viscosity and modulus resulting in a 3 orders of magnitude change from a solid (20,000 Pa) to a liquid (50 Pa) at rate of 13,500 Pa/s. Subsequent exposure to visible light reverses the transition, returning the viscosity essentially to its initial state. Such large, rapid, and reversible changes in rheological properties within this LLC system may open a door to new applications for photorheological fluids.

No abstract

Stable graphene oxide monoliths (GOMs) have been fabricated by exploiting epoxy groups on the surface of graphene oxide (GO) in a ring opening reaction with amine groups of poly(oxypropylene) diamines (D400). This method can rapidly form covalently bonded GOM with D400 within 60 s. FTIR and XPS analyses confirm the formation of covalent C‐N bonds. Investigation of the GOM formation mechanism reveals that the interaction of GO with a diamine cross‐linker can result in 3 different GO assemblies depending on the ratio of D400 to GO, which have been proven both by experiment and molecular dynamics calculations. Moreover, XRD results indicate that the interspacial distance between GO sheets can be tuned by varying the diamine chain length and concentration. We demonstrate that the resulting GOM can be moulded into various shapes and behaves like an elastic hydrogel. The fabricated GOM is non‐cyctotoxic to L929 cell lines indicating a potential for biomedical applications. It could also be readily converted to graphene monolith upon thermal treatment. This new rapid and facile method to prepare covalently cross‐linked GOM may open the door to the synthesis and application of next generation multifunctional 3D graphene structures.

The aged eye's ability to change focus (accommodation) may be restored by replacing the hardened natural lens with a soft gel. Functionalised polysiloxane macromonomers, designed for application as an injectable, in situ curable accommodating intraocular lens (A-IOL), were prepared via a twostep synthesis. Prepolymers were synthesised via ring opening polymerisation (ROP) of octamethylcyclotetrasiloxane (D 4 ) and 2,4,6,8-tetramethylcyclotetrasiloxane (D 4 H ) in toluene using trifluoromethanesulfonic acid (TfOH) as catalyst. Hexaethyldisiloxane (HEDS) was used as the end group to control the molecular weight of the prepolymers, which were then converted to macromonomers by hydrosilylation of the SiH groups with allyl methacrylate (AM) to introduce polymerisable groups. The resulting macromonomers had an injectable consistency and thus, were able to be injected into and refill the empty lens capsular bag. The macromonomers also contained a low ratio of polymerisable groups so that they may be cured on demand, in situ, under irradiation of blue light, in the presence of a photo-initiator, to form a soft polysiloxane gel (an intraocular lens) in the eye. The pre-cure viscosity and post-cure modulus of the polysiloxanes, which are crucial factors for an injectable, in situ curable A-IOL application, were controlled by adjusting the end group and D 4 H concentrations, respectively, in the ROP. The macromonomers were fully cured within 5 minutes under light irradiation, as shown by the rapid change in modulus monitored by photorheology. Ex vivo primate lens stretching experiments on an Ex Vivo Accommodation Simulator (EVAS) showed that the polysiloxane gel refilled lenses achieved over 60% of the accommodation amplitude of the natural lens. An in vivo biocompatibility study in rabbits using the lens refilling (Phaco-Ersatz) procedure demonstrated that the soft gels were biocompatible with the ocular tissue. The polysiloxane macromonomers meet the targeted optical and mechanical properties of a young natural crystalline lens and show promise as candidate materials for use as injectable, in situ curable A-IOLs for lens refilling procedures.

We report two photoresponsive amphiphiles with comparable structures consisting of hydrophilic oligooxyethylene units, a hydrophobic alkyl chain and a light-sensitive azobenzene moiety, demonstrating that self-assembly and photoresponsive behaviour is extremely sensitive to the position of the photoactive moiety within the surfactant molecular architecture.

We present for the first time a real-time small-angle X-ray scattering (SAXS) study of the structural transition of fluid microemulsion to solid polymerized material in a silicone polymerizable microemulsion system. A reactive methacrylate-terminated siloxane macromonomer (MTSM, M n ∼ 1000 g/mol) was synthesized and used for microemulsion formulations comprising MTSM (oil phase), water, and a mixture of nonionic surfactant (Teric G 9 A 8 ) with isopropanol. In situ synchrotron SAXS was used to investigate time-dependent nanostructure evolution during the polymerization reaction, which was directly initiated by X-ray radiation. The SAXS data were analyzed using both the TeubnerÀStrey model and the coreÀshell model. The results obtained by the TeubnerÀStrey model showed that the domain size (d) decreased while the correlation length (ξ) increased upon polymerization. The analysis in terms of the coreÀshell model displayed that adding water to the precursor microemulsion caused the water droplets to start swelling, which resulted in the discontinuity of water in oil microemulsion. There exhibited large differences in morphologies of polymerized materials from the microemulsion formulations with different water and surfactant contents. The core and shell sizes of water droplets decreased during the course of polymerization when there was 15 wt % or more water in the microemulsion formulation; the polymerized material thus exhibited increasingly discrete granular morphology. When there was 10 wt % or less water content in the precursor microemulsion, the rearrangement of water domains could be minimized during the course of polymerization and transparent polymerized material was obtained.