Gelatin-Based Photocurable Hydrogels for Corneal Wound Repair.

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.

2-N, 6-O-sulfated chitosan-assisted BMP-2 immobilization of PCL scaffolds for enhanced osteoinduction.

The aim of this study was to develop a 2-N, 6-O-sulfated chitosan (26SCS) modified electrospun fibrous PCL scaffold for bone morphogenetic protein-2 (BMP-2) delivery to improve osteoinduction. The PCL scaffold was modified by an aminolysis reaction using ethylenediamine (ED) and 26SCS was immobilized via electrostatic interactions (PCL-N-S). Scaffolds were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements.

A QCM-D and SAXS Study of the Interaction of Functionalised Lyotropic Liquid Crystalline Lipid Nanoparticles with siRNA.

Biophysical studies were undertaken to investigate the binding and release of short interfering ribonucleic acid (siRNA) from lyotropic liquid crystalline lipid nanoparticles (LNPs) by using a quartz crystal microbalance (QCM). These carriers are based on phytantriol (Phy) and the cationic lipid DOTAP (1,2-dioleoyloxy-3-(trimethylammonium)propane). The nonlamellar phase LNPs were tethered to the surface of the QCM chip for analysis based on biotin-neutravidin binding, which enabled the controlled deposition of siRNA-LNP complexes with different lipid/siRNA charge ratios on a QCM-D crystal sensor.

Formation and characterisation of a modifiable soft macro-porous hyaluronic acid cryogel platform.

A facile method for the synthesis of cell supportive, highly macro-porous hyaluronic acid (HA) hydrogels via cryogelation is presented. Unmodified HA was chemically cross-linked via EDC/NHS zero-length cross-linking at sub-zero temperatures to yield cryogels with high porosity and high pore interconnectivity. The physical properties of the HA cryogels including porosity, average pore size, elasticity and swelling properties were characterised as a function of cryogelation conditions and composition of the precursor solution.

Evaluation of an established pericardium patch for delivery of mesenchymal stem cells to cardiac tissue.

The present study has evaluated a commercial pericardial material for its capacity to assist as a natural extracellular matrix (ECM) patch for the delivery and retention of mesenchymal stem cells for cardiac repair. The repair of cardiac tissue with cells delivered by an appropriate bioscaffold is expected to offer a superior, long-lasting treatment strategy. The present material, CardioCel®, is based on acellular pericardium that has been stabilized by treatments, including a low concentration of glutaraldehyde, that eliminate calcification after implantation.

Size and phase control of cubic lyotropic liquid crystal nanoparticles.

The effective use of lyotropic liquid crystalline dispersions, such as cubosomes, as drug delivery vehicles requires that they have tailored physical characteristics that suit specific therapeutics and external conditions. Here, we have developed phytantriol-based cubosomes from a dispersion of unilamellar vesicles and show that we can control their size as well as the critical packing parameter (CPP) of the amphiphilic bilayer through regulation of temperature and salt concentration, respectively. Using the anionic biological lipid 1,2-dipalmi-toylphosphatidylserine (DPPS) to prevent the cubic phase from forming, we show that the addition of phosphate buffered saline (PBS) results in a transition from small unilamellar vesicles to the cubic phase due to charge-shielding of the anionic lipid.

Atmospheric pressure plasmas: infection control and bacterial responses.

Cold atmospheric pressure plasma (APP) is a recent, cutting-edge antimicrobial treatment. It has the potential to be used as an alternative to traditional treatments such as antibiotics and as a promoter of wound healing, making it a promising tool in a range of biomedical applications with particular importance for combating infections. A number of studies show very promising results for APP-mediated killing of bacteria, including removal of biofilms of pathogenic bacteria such as Pseudomonas aeruginosa.

Bone regeneration using photocrosslinked hydrogel incorporating rhBMP-2 loaded 2-N, 6-O-sulfated chitosan nanoparticles.

Although rhBMP-2 has excellent ability to accelerate the repair of normal bone defects, limitations of its application exist in the high cost and potential side effects. This study aimed to develop a composite photopolymerisable hydrogel incorporating rhBMP-2 loaded 2-N, 6-O-sulfated chitosan nanoparticles (PH/rhBMP-2/NPs) as the bone substitute to realize segmental bone defect repair at a low growth factor dose. Firstly rhBMP-2 loaded 2-N, 6-O-sulfated chitosan nanoparticles (rhBMP-2/NPs) were prepared and characterized by DLS and TEM.

Emerging rules for effective antimicrobial coatings.

In order to colonize abiotic surfaces, bacteria and fungi undergo a profound change in their biology to form biofilms: communities of microbes embedded into a matrix of secreted macromolecules. Despite strict hygiene standards, biofilm-related infections associated with implantable devices remain a common complication in the clinic. Here, the application of highly dosed antibiotics is problematic in that the biofilm (i) provides a protective environment for microbes to evade antibiotics and/or (ii) can provide selective pressure for the evolution of antibiotic-resistant microbes.

Targeted detection of phosphatidylserine in biomimetic membranes and in vitro cell systems using annexin V-containing cubosomes.

In this work we have formulated Annexin V (ANX) decorated phosphatidylserine containing phytantriol (PSPhy) cubosomes to act as probes for the enhanced detection of apoptotic membranes in both model and in vitro cell systems. Small angle X-ray scattering (SAXS) and cryogenic-transmission electron microscopy (Cryo-TEM) indicated that ANX-containing PSPhy (ANX-PSPhy) cubosomes retain the Pn3m cubic symmetry and cubic phase nanoparticle characteristics of PSPhy cubosomes. The interaction of ANX-PSPhy cubosomes with apoptotic model and cellular membranes was also investigated using both quartz crystal microbalance with dissipation and confocal microscopy which confirmed that ANX-PSPhy cubosomes can selectively bind to apoptotic cells and model membranes.

Cryogels for biomedical applications.

The use of hydrogels as support materials for the growth and proliferation of mammalian cells has been well documented as they closely mimic the gel-like properties - and in some cases also the chemical properties - of the extracellular matrix (ECM), which naturally surrounds the cells of any biological tissue. Macro-porous hydrogels set below the freezing point of the solvent, so-called 'cryogels', have recently gained significant interest in the fields of tissue engineering and in vitro cell culture, thanks to their inherent interconnected macro-porous structure and ease of formation in comparison to other macro-pore forming techniques. This review highlights recent advances in cryogelation techniques and starting materials that can be utilised to synthesise biocompatible and biologically relevant cryogels as well as discussing physicochemical characterisation techniques for these materials.

Self-assembly of ciprofloxacin and a tripeptide into an antimicrobial nanostructured hydrogel.

This work reports the self-assembly of a sparingly soluble antibiotic (ciprofloxacin) and a hydrophobic tripeptide ((D)Leu-Phe-Phe) into supramolecular nanostructures that yield a macroscopic hydrogel at physiological pH. Drug incorporation results in modified morphology and rheological properties of the self-assembled hydrogel. These changes can be correlated with intermolecular interactions between the drug and the peptide, as confirmed by spectroscopic analysis (fluorescence, circular dichroism, IR).

The effect of RAFT-derived cationic block copolymer structure on gene silencing efficiency.

In this work a series of ABA tri-block copolymers was prepared from oligo(ethylene glycol) methyl ether methacrylate (OEGMA(475)) and N,N-dimethylaminoethyl methacrylate (DMAEMA) to investigate the effect of polymer composition on cell viability, siRNA uptake, serum stability and gene silencing. Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization was used as the method of polymer synthesis as this technique allows the preparation of well-defined block copolymers with low polydispersity. Eight block copolymers were prepared by systematically varying the central cationic block (DMAEMA) length from 38 to 192 monomer units and the outer hydrophilic block (OEGMA(475)) from 7 to 69 units.

Glycerol monooleate-based nanocarriers for siRNA delivery in vitro.

We present studies of the delivery of short interfering ribonucleic acid (siRNA) into a green fluorescent protein (GFP) expressing cell line, using lipid nanocarriers in cubic lyotropic liquid crystal form. These carriers are based on glycerol monooleate (GMO) and employ the use of varying concentrations of cationic siRNA binding lipids. The essential physicochemical parameters of the cationic lipid/GMO/siRNA complexes such as particle size, ζ otential, siRNA uptake stability, lyotropic mesophase behavior, cytotoxicity,and gene silencing efficiency were systematically assessed.

Photoinitiated alkyne-azide click and radical cross-linking reactions for the patterning of PEG hydrogels.

The photolithographical patterning of hydrogels based solely on the surface immobilization and cross-linking of alkyne-functionalized poly(ethylene glycol) (PEG-tetraalkyne) is described. Photogenerated radicals as well as UV absorption by a copper chelating ligand result in the photochemical redox reduction of Cu(II) to Cu(I). This catalyzes the alkyne-azide click reaction to graft the hydrogels onto an azide-functionalized plasma polymer (N(3)PP) film.

One step multifunctional micropatterning of surfaces using asymmetric glow discharge plasma polymerization.

Micropatterning of surfaces with varying chemical, physical and topographical properties usually requires a number of fabrication steps. Herein, we describe a micropatterning technique based on plasma enhanced chemical vapour deposition (PECVD) that deposits both protein resistant and protein repellent surface chemistries in a single step. The resulting multifunctional, selective surface chemistries are capable of spatially controlled protein adhesion, geometric confinement of cells and the site specific confinement of enzyme mediated peptide self-assembly.

An X-ray and neutron reflectometry study of 'PEG-like' plasma polymer films.

Plasma-enhanced chemical vapour-deposited films of di(ethylene glycol) dimethyl ether were analysed by a combination of X-ray photoelectron spectroscopy, atomic force microscopy, quartz crystal microbalance with dissipation monitoring (QCM-D), X-ray and neutron reflectometry (NR). The combination of these techniques enabled a systematic study of the impact of plasma deposition conditions upon resulting film chemistry (empirical formula), mass densities, structure and water solvation, which has been correlated with the films' efficacy against protein fouling. All films were shown to contain substantially less hydrogen than the original monomer and absorb a vast amount of water, which correlated with their mass density profiles.

The influence of surface topography of a porous perfluoropolyether polymer on corneal epithelial tissue growth and adhesion.

Design principles for corneal implants are challenging and include permeability which inherently involves pore openings on the polymer surface. These topographical cues can be significant to a successful clinical outcome where a stratified epithelium is needed over the device surface, such as with a corneal onlay or corneal repair material. The impact of polymer surface topography on the growth and adhesion of corneal epithelial tissue was assessed using porous perfluoropolyether membranes with a range of surface topography.

New insights into the substrate-plasma polymer interface.

We describe a new method to characterize the underside (substrate interface) of plasma polymer (PP) thin films via their simple delamination from a sodium chloride single crystal substrate. By depositing the PP film onto an ionic bonded surface such as a sodium chloride crystal, the PP films investigated were easily delaminated from the substrate. Two plasma polymer films deposited from 1-bromopropane (BrPP) and allylamine (AAPP) were used to exemplify this new technique.

The in vivo performance of an enzyme-assisted self-assembled peptide/protein hydrogel.

We demonstrate the distribution of the important extracellular matrix protein laminin in a novel biomaterial consisting of a hydrogel underpinned by nanofibrillar networks. These are formed by the immobilised enzyme mediated self-assembly of fmoc-L(3) (9-fluorenylmethoxycarbonyl-tri-leucine). The peptide assembly yields nanofibrils formed of β-sheets that are locked together via π-stacking interactions.

A perfluoropolyether corneal inlay for the correction of refractive error.

This study assessed the long-term biological response of a perfluoropolyether-based polymer developed as a corneal inlay to correct refractive error. The polymer formulation met chemical and physical specifications and was non-cytotoxic when tested using standard in vitro techniques. It was cast into small microporous membranes that were implanted as inlays into corneas of rabbits (n = 5) and unsighted humans (n = 5 + 1 surgical control) which were monitored for up to 23 and 48 months respectively.

The influence of dipalmitoyl phosphatidylserine on phase behaviour of and cellular response to lyotropic liquid crystalline dispersions.

Lyotropic liquid crystalline nanoparticles (cubosomes) have the potential to act as amphiphilic scaffolds for the presentation of lipids and subsequent application in, for example, bioseparations and therapeutic delivery. In this work we have formulated lyotropic liquid crystalline systems based on the synthetic amphiphile 1,2,3-trihydroxy-3,7,11,15-tetramethylhexadecane (phytantriol) and containing the lipid dipalmitoyl phosphatidylserine (DPPS). We have prepared a range of DPPS-containing phytantriol cubosome formulations and characterized them using Small Angle X-ray Scattering and Cryo-transmission electron microscopy.

One-step method for generating PEG-like plasma polymer gradients: chemical characterization and analysis of protein interactions.

In this work we report a one-step method for the fabrication of poly(ethylene glycol) PEG-like chemical gradients, which were deposited via continuous wave radio frequency glow discharge plasma polymerization of diethylene glycol dimethyl ether (DG). A knife edge top electrode was used to produce the gradient coatings at plasma load powers of 5 and 30 W. The chemistry across the gradients was analyzed using a number of complementary techniques including spatially resolved synchrotron source grazing incidence FTIR microspectroscopy, X-ray photoelectron spectroscopy (XPS) and synchrotron source near edge X-ray absorption fine structure (NEXAFS) spectroscopy.

Fabrication of asymmetric "Janus" particles via plasma polymerization.

A versatile approach has been developed using plasma polymerization to fabricate functional Janus particles. A brominated plasma polymer is toposelectively deposited on a monolayer of silica microparticles, endowing the particles with a chemically reactive polymeric and silica hemisphere.