Use of in vitro and haptic assessments in the characterisation of surface lubricity

Lubricity is a key property of hydrophilic-coated urinary catheter surfaces. In vitro tests are commonly employed for evaluation of surface properties in the development of novel catheter coating technologies, however, their value in predicting the more subjective feeling of lubricity requires validation. We herein perform a range of in vitro assessments and human organoleptic studies to characterise surface properties of developmental hydrophilic coating formulations, including water wettability, coefficient of friction, dry-out kinetics and lubricity. Significant reductions of up to 40% in the contact angles and coefficient of friction values of the novel coating formulations in comparison to the control poly(vinyl pyrrolidone)-coated surfaces were demonstrated during quantitative laboratory assessments. In contrast, no significant differences in the more subjective feeling of lubricity between the novel formulations and the control-coated surfaces were observed when formulations were haptically assessed by the techniques described herein. This study, importantly, highlights the need for optimisation of in vitro and human haptic assessments to more reliably predict patient preferences

Antibacterial assessment of TMPyP-incorporated p(HEMA-co-MMA)

IntroductionLight-triggered therapy to treat infectious diseases is called photodynamic antimicrobial therapy (PACT).PACT has been widely shown to have a lethal effect against bacteria, fungi, viruses, and parasites and it impacts different biofilms (Garcez et al., 2007) TMPyP (tetrakis(4-N-methylpyridyl)porphyrin) is a porphyrin frequently used in PACT, and exerts its phototoxic effect upon both gram-negative and gram-positive bacteria, via two reactions First, Type II reaction is considered the major pathway of photodynamic therapy. The second pathway, Type I reaction, involves transferring electrons/protons to a substrate and releasing a radical that can react with oxygen to produce reactive oxygen species (ROS) (Brady et al., 2007). This study aims to develop a novel surface loading with TMPyP capable of reducing the adherence of bacteria.Materials and methodsTMPyP (tetrakis(4-N-methylpyridyl)porphyrin) IS the photosensitizer loaded into p(HEMA-co-MMA)hydrogel. S. aureus ATCC 29213 and E. coli ATCC 700928 which are required for the microbiological assessments. The LED light array activates TMPyP-incorporated p(HEMA-co-MMA). TMPyP was incorporated onto the surface of the p(HEMA-co-MMA) copolymer by swell-encapsulation shrink(SES) technique. Samples were prepared by loading them in different TMPyP soaking solutions for 2min. First, a TMPyP stock solution was prepared (2.18 mg/ml). Next, further dilutions to the appropriate concentration were made using PBS (at pH 7.4). S. aureus ATCC 29213 and E. coli ATCC 700928 represent gram-positive and gram-negative bacteria and are used for assessing adherence percentages.ResultsThe percentage adherence (%) compared to dark control of S. aureus and E. coli when TMPyP-incorporated and unincorporated p(HEMA-co-MMA) were illuminated for 120 min using a whiteLED source providing a power of 5.33 mW/cm2, integrated between 450–700 nm, or in dark condition has been presented in Figure 1.DiscussionTMPyP incorporated copolymers (7.33x10-4 M and7.33x10-5 M) significantly reduced the percentage adherence of S. aureus and E. coli compared to dark control illustrating that these materials are less likely to colonize. This antimicrobial behaviour for hydrogels loaded with 7.33x10-4 M of TMPyP shows significant promise for the development of biomaterials to prevent the colonization of gram-positive and gram-negative bacteria and prevent biofilm formation.ConclusionOverall, the attachment of TMPyP into the surface of p(HEMA-co-MMA) copolymers resulted in a material with antimicrobial behaviour

Photochemically controlled drug dosing from a polymeric scaffold

Purpose To develop the first photoactive biomaterial coating capable of controlled drug dosing via inclusion of synthesised drug-3,5-dimethoxybenzoin (DMB) conjugates in a poly(2-methyoxyethyl acrylate) (pMEA) scaffold. Methods Flurbiprofen- and naproxen-DMB conjugates were prepared via esterification and characterised via NMR spectroscopy and mass spectrometry following chromatographic purification. Conjugate photolysis was investigated in acetonitrile solution and within the pMEA matrix following exposure to low-power 365 nm irradiation. Photo-liberation of drug from pMEA into phosphate buffered saline was monitored using UV-vis spectroscopy. Results The synthetic procedures yielded the desired drug conjugates with full supporting characterisation. Drug regeneration through photolysis of the synthesised conjugates was successful in both acetonitrile solution and within the pMEA scaffold upon UV irradiation. Conjugates were retained within the pMEA scaffold with exclusive drug liberation following irradiation and increased drug dose with increasing exposure. Multi-dosing capacity was demonstrated though the ability of successive irradiation periods to generate further bursts of drug. Conclusion This study demonstrates the first application of photochemically controlled drug release from a biomaterial coating and the feasibility of using pMEA as a scaffold for housing the photoactive drug-DMB conjugates

Hydrogel-forming microneedle arrays made from light-responsive materials for on-demand transdermal drug delivery

We describe, for the first time, stimuli-responsive hydrogel-forming microneedle (MN) arrays that enable delivery of a clinically-relevant model drug (ibuprofen) upon application of light. MN arrays were prepared using a polymer prepared from 2-hydroxyethyl methacrylate (HEMA) and ethylene glycol dimethacrylate (EGDMA) by micromolding. The obtained MN arrays showed good mechanical properties. The system was loaded with up to 5% (w/w) ibuprofen included in a light-responsive 3,5-dimethoxybenzoin conjugate. Raman spectroscopy confirmed the presence of the conjugate inside the polymeric MN matrix. In vitro, this system was able to deliver up to three doses of 50 mg of ibuprofen upon application of an optical trigger over a prolonged period of time (up to 160 hours). This makes the system appealing as a controlled release device for prolonged periods of time. We believe that this technology has potential for use in “on-demand” delivery of a wide range of drugs in a variety of applications relevant to enhanced patient care

Systematic optimization of poly(vinyl chloride) surface modification with an aromatic thiol

Abstract The efficient covalent functionalization of poly(vinyl chloride) (PVC), which is widely used in medical device manufacture, allows an array of potential property-enhancing surface modifications to be made. To demonstrate a general method of functionalization via substituted (functional) thiols, we describe a systematic approach to the optimization of PVC surface modification by nucleophilic substitution with 4-aminothiophenol through control of reaction conditions: solvent composition, sonication, reaction time and presence of base and/or phase transfer catalyst (PTC). Efficient thiol attachment was confirmed using solid-state NMR and Raman spectroscopies, and the extent of surface modification was quantified using ATR-FTIR spectroscopy. Sonicated samples exhibited a lower degree of modification than their statically immersed counterparts (21.7 vs 99.6 μg cm-3), and mechanical integrity was compromised. In DMSO/H2O systems with a PTC, resultant degrees of PVC surface modification were up to 12.5% higher when caesium carbonate was employed as the base than in corresponding systems with potassium carbonate