Bacterial biofilm colonization and succession in tropical marine waters are similar across different types of stone materials used in seawall construction.

Seawalls are important in protecting coastlines from currents, erosion, sea-level rise, and flooding. They are, however, associated with reduced biodiversity, due to their steep orientation, lack of microhabitats, and the materials used in their construction. Hence, there is considerable interest in modifying seawalls to enhance the settlement and diversity of marine organisms, as microbial biofilms play a critical role facilitating algal and invertebrate colonization. We assessed how different stone materials, ranging from aluminosilicates to limestone and concrete, affect biofilm formation. Metagenomic assessment of marine microbial communities indicated no significant impact of material on microbial diversity, irrespective of the diverse surface chemistry and topography. Based on KEGG pathway analysis, surface properties appeared to influence the community composition and function during the initial stages of biofilm development, but this effect disappeared by Day 31. We conclude that marine biofilms converged over time to a generic marine biofilm, rather than the underlying stone substrata type playing a significant role in driving community composition.

Long-Term Subconjunctival Delivery of Brimonidine Tartrate for Glaucoma Treatment Using a Microspheres/Carrier System.

Core-shell polymer microspheres with poly(d,l-lactic-co-glycolic acid) core and poly(l-lactic acid) (PLLA) shell are developed for the long-term subconjunctival release of brimonidine tartrate (BT) in order to reduce intraocular pressure (IOP) in the treatment of glaucoma. The PLLA-rich shell acts as a diffusion barrier, enabling linear release of BT over an extended period of 40 d. The microspheres are encased in a porous non-degradable methacrylate-based carrier for ease of subconjunctival implantation in a glaucoma-induced rabbit model. In vivo release of BT from the microspheres/carrier system has enabled a significant, immediate IOP reduction of 20 mmHg, which is sustained for 55 d. Long-term IOP reduction may be maintained by periodic replacement of the microspheres/carrier system.

Transparent nanostructured photochromic UV-blocking soft contact lenses.

AIM: We aim to develop transparent UV-blocking photochromic soft contact lenses via polymerization of a bicontinuous nanoemulsion. MATERIALS & METHODS: Transparent nanostructured polymers were prepared by incorporating a polymerizable surfactant and thermal initiator together with water, monomers, UV blockers and photochromic dyes. The polymers were characterized using oxygen permeometer, tensile tester, electron microscope, UV spectrophotometer, corneal cell culture and testing in rabbits. RESULTS: The polymers have good oxygen permeability, water content, stiffness, strength and UV-blocking ability comparable to commercial UV-blocking soft contact lenses. Their response to UV light is comparable to photochromic spectacle lenses, particularly in reverse transition from colored to colorless state. They are nontoxic and nonleaching. CONCLUSION: Our photochromic UV-blocking contact lenses provide a novel alternative to photochromic spectacles.

Sustained release of bupivacaine for post-surgical pain relief using core-shell microspheres.

Core-shell polymer microspheres with poly(d,l-lactic-co-glycolic acid) (PLGA) core and poly(l-lactic acid) (PLLA) shell were developed for sustained release of bupivacaine for postoperative pain relief after knee surgery. The PLLA-rich shell acted as a diffusion barrier, allowing linear release of bupivacaine in a goat model over an extended period of 2 weeks post-surgery. In vivo bupivacaine concentrations in the goat synovial fluid remained within therapeutic levels for the 2 weeks, whereas bupivacaine concentrations in the blood plasma remained safely below toxic levels. All animals survived until the end of the 28 day study, with no inflammation, infection or reduced mobility. Explantation at day 28 revealed some soft microsphere remnants in the para-patellar space of the knee joint. However, there was no damage to the articular surfaces, or interference with joint motion. Histological analysis of each knee compartment did not reveal any signs of osteoarthrosis or degeneration within the joints, and safranin-O staining showed intact cartilage surfaces with well-preserved proteoglycan content.

Delivery of chemotropic proteins and improvement of dopaminergic neuron outgrowth through a thixotropic hybrid nano-gel.

Chemotropic proteins guide neuronal projections to their final target during embryo development and are useful to guide axons of neurons used in transplantation therapies. Site-specific delivery of the proteins however is needed for their application in the brain to avoid degradation and pleiotropic affects. In the present study we report the use of Poly (ethylene glycol)-Silica (PEG-Si) nanocomposite gel with thixotropic properties that make it injectable and suitable for delivery of the chemotropic protein semaphorin 3A. PEG-Si gel forms a functional gradient of semaphorin that enhances axon outgrowth of dopaminergic neurons from rat embryos or differentiated from stem cells in culture. It is not cytotoxic and its properties allowed its injection into the striatum without inflammatory response in the short term. Long term implantation however led to an increase in macrophages and glial cells. The inflammatory response could have resulted from non-degraded silica particles, as observed in biodegradation assays.

The effect of matrix stiffness on mesenchymal stem cell differentiation in a 3D thixotropic gel.

Recent studies have demonstrated the effect of matrix stiffness on the phenotype and differentiation pathway of mesenchymal stem cells (MSCs). MSCs differentiated into neural, myogenic or osteogenic phenotypes depending on whether they were cultured on two-dimensional (2D) substrates of elastic moduli in the lower (0.1-1 kPa), intermediate (8-17 kPa) or higher ranges (34 kPa). In this study, MSCs were cultured in thixotropic gels of varying rheological properties, and similar results were found for the three-dimensional (3D) culture as for the previous findings in 2D culture. For the 3D cell cultures in thixotropic gels, the liquefaction stress (tau(y)), the minimum shear stress required to liquefy the gel, was used to characterize the matrix stiffness. The highest expressions of neural (ENO2), myogenic (MYOG) and osteogenic (Runx2, OC) transcription factors were obtained for gels with tau(y) of 7, 25 and 75 Pa, respectively. Immobilization of the cell-adhesion peptide, RGD, promoted both proliferation and differentiation of MSCs, especially for the case of the stiffer gels (>75 Pa). This study demonstrated the usefulness of thixotropic gels for 3D cell culture studies, as well as the use of tau(y) as an effective measure of matrix stiffness that could be correlated to MSC differentiation.

The development of a nanocrystalline apatite reinforced crosslinked hyaluronic acid-tyramine composite as an injectable bone cement.

We have developed an injectable bone cement composed of nanocrystalline apatite and crosslinked hyaluronic acid-tyramine conjugates (HA-Tyr). This bone cement was formed via the oxidative coupling of tyramine moieties catalyzed by hydrogen peroxide (H(2)O(2)) and horseradish peroxidase (HRP). The bone cement set within 60s after H(2)O(2) and HRP were added to the apatite/HA-Tyr pastes. The mechanical strength of the apatite/HA-Tyr cement was tuned by varying the apatite loading and H(2)O(2) concentration. This rapid enzyme-mediated setting of our bone cement results in minimal heat release (DeltaH=-11.39 J/g) as compared to conventional bone cements. The crystalline phase and crystallite size (20 nm) of the apatitic phase in our bone cement matched that of trabecular bone. The storage modulus (G'), yield stress (sigma(y)), and compressive stiffness (E(c)) of our bone cement prepared with different apatite loadings and H(2)O(2) concentrations were measured, and optimized at G'=40 MPa, sigma(y)=0.308 MPa and E(c)=2.270 MPa when the cement was formed with 0.4 g/ml of apatite, 0.61 units/ml of HRP and 6.8 mm of H(2)O(2). Our biocompatible bone cement also successfully healed small bone and joint defects in mice within 8 weeks.

A thixotropic nanocomposite gel for three-dimensional cell culture.

Thixotropic materials, which become less viscous under stress and return to their original state when stress is removed, have been used to deliver gel-cell constructs and therapeutic agents. Here we show that a polymer-silica nanocomposite thixotropic gel can be used as a three-dimensional cell culture material. The gel liquefies when vortexed--allowing cells and biological components to be added--and resolidifies to trap the components when the shear force from spinning is removed. Good permeability of nutrients and gases through the gel allows various cell types to proliferate and be viable for up to three weeks. Human mesenchymal stem cells cultured in stiffer gels developed bone-like behaviour, showing that the rheological properties of the gel can control cell differentiation. No enzymatic, chemical, or photo-crosslinking, changes in ionic strength or temperature are required to form or liquefy the gel, offering a way to sub-culture cells without using trypsin-a protease commonly used in traditional cell culture techniques.