Characterization of the Rheological, Mucoadhesive, and Drug Release Properties of Highly Structured Gel Platforms for Intravaginal Drug Delivery

This investigation describes the formulation and characterization of theologically structured vehicles (RSVs) designed for improved drug delivery to the vagina. Interactive, multicomponent, polymeric platforms were manufactured containing hydroxyethylcellulose (HEC, 5% w/w) polyvinylpyrrolidone (PVP, 4% w/w), Pluronic (PL, 0 or 10% w/w), and either polycarbophil (PC, 3% w/w) or poly(methylvinylether-co-maleic anhydride) (Gantrez S97, 3% w/w) as a mucoadhesive agent. The rheological (torsional and dynamic), mechanical (compressional), and mucoadhesive properties were characterized and shown to be dependent upon the mucoadhesive agent used and the inclusion/exclusion of PL. The dynamic theological properties of the gel platforms were also assessed following dilution with simulated vaginal fluid (to mimic in vivo dilution). RSVs containing PC were more rheologically structured than comparator formulations containing GAN. This trend was also reflected in formulation hardness, compressibility, consistency, and syringeability. Moreover, formulations containing PL (10% w/w) were more theologically structured than formulations devoid of PL. Dilution with simulated vaginal fluids significantly decreased rheological structure, although RSVs still retained a highly elastic stnicture (G' > G '' and tan delta <1). Furthermore, RSVs exhibited sustained drug release properties that were shown to be dependent upon their rheological structure. It is considered that these semisolid drug delivery systems may be useful as site-retentive platforms for the sustained delivery of therapeutic agents to the vagina.

Key biological issues in contact lens development

A contact lens is a medical device widely used as an alternative to spectacles in order to correct refractive vision problems. The evolution of polymeric biomaterials has heralded a continuous development in the materials used to produce contact lenses and maximize patient comfort and limit adverse events. Microbial keratitis (MK) is a relatively rare but potentially devastating condition associated with contact lens use, particularly with the extended wear of hydrogel lenses. It is the principal complication related to contact lens wear and the large population at risk make it a public health concern. Bacterial binding to the contact lens material is a precursor to the development of MK and is influenced by properties of the material and the bacteria. In order for bacteria to infiltrate the cornea there must be some degree of corneal damage, usually caused by trauma or hypoxia. The most recent materials available aim to allow the continuous wear of lenses while limiting corneal hypoxia, thus helping to prevent the development of MK. Limitations to the treatment of MK require that novel approaches may be necessary in order to limit bacterial adhesion to contact lens materials.

Incorporation of multiwalled carbon nanotubes to acrylic based bone cements: Effects on mechanical and thermal properties

Polymethyl methacrylate (PMMA) bone cement–multiwalled carbon nanotube (MWCNT) nanocomposites with a weight loading of 0.1% were prepared using 3 different methods of MWCNT incorporation. The mechanical and thermal properties of the resultant nanocomposite cements were characterised in accordance with the international standard for acrylic resin cements. The mechanical properties of the resultant nanocomposite cements were influenced by the type of MWCNT and method of incorporation used. The exothermic polymerisation reaction for the PMMA bone cement was significantly reduced when thermally conductive functionalised MWCNTs were added. This reduction in exotherm translated in a decrease in thermal necrosis index value of the respective nanocomposite cements, which potentially could reduce the hyperthermia experienced in vivo. The morphology and degree of dispersion of the MWCNTs in the PMMA matrix at different scales were analysed using scanning electron microscopy. Improvements in mechanical properties were attributed to the MWCNTs arresting/retarding crack propagation through the cement by providing a bridging effect into the wake of the crack, normal to the direction of crack growth. MWCNT agglomerations were evident within the cement microstructure, the degree of these agglomerations was dependent on the method used to incorporate the MWCNTs into the cement.

Metamaterial made of paired planar conductors: Particle resonances, phenomena and properties

The properties and characteristics of a recently proposed anisotropic metamaterial based upon layered arrays of tightly coupled pairs of "dogbone" shaped stripe conductors have been explored in detail. It has been found that a metamaterial composed of such stacked layers exhibits artificial magnetism and may support backward wave propagation. The equivalent network models of the constitutive conductor pairs arranged in the periodic array have been devised and applied to the identification of the specific types of resonances, and to the analysis of their contribution into the effective dielectric and magnetic properties of the artificial medium. The proposed "dogbone" configuration of conductor pairs has the advantage of being entirely realizable and assemblable in planar technology. It also appears more prospective than simple cut-wire or metal-plate pairs because the additional geometrical parameters provide an efficient control of separation between the electric and magnetic resonances that, in turn, makes it possible to obtain a fairly broadband left-handed behaviour of the structure at low frequencies.

The modification of PLA and PLGA using electron-beam radiation

The degradable polymers polylactide (PLA) and polylactide-co-glycolide (PLGA) have found widespread use in modern medical practice. However, their slow degradation rates and tendency to lose strength before mass have caused problems. The aim of this study was to ascertain whether treatment with e-beam radiation could address these problems. Samples of PLA and PLGA were manufactured and placed in layered stacks, 8.1 mm deep, before exposure to 50 kGy of e-beam radiation from a 1.5 MeV accelerator. Gel permeation chromatography testing showed that the molecular weight of both materials was depth-dependent following irradiation, with samples nearest to the treated surface showing a reduced molecular weight. Samples deeper than 5.4 mm were unaffected. Computer modeling of the transmission of a 1.5 MeV e-beam in these materials corresponded well with these findings. An accelerated mass-loss study of the treated materials found that the samples nearest the irradiated surface initiated mass loss earlier, and at later stages showed an increased percentage mass loss. It was concluded that e-beam radiation could modify the degradation of bioabsorbable polymers to potentially improve their performance in medical devices, specifically for improved orthopedic fixation.

Raman microscopy in the diagnosis and prognosis of surgically resected nonsmall cell lung cancer

The main curative therapy for patients with nonsmall cell lung cancer is surgery. Despite this, the survival rate is only 50%, therefore it is important to more efficiently diagnose and predict prognosis for lung cancer patients. Raman spectroscopy is useful in the diagnosis of malignant and premalignant lesions. The aim of this study is to investigate the ability of Raman microscopy to diagnose lung cancer from surgically resected tissue sections, and predict the prognosis of these patients. Tumor tissue sections from curative resections are mapped by Raman microscopy and the spectra analzsed using multivariate techniques. Spectra from the tumor samples are also compared with their outcome data to define their prognostic significance. Using principal component analysis and random forest classification, Raman microscopy differentiates malignant from normal lung tissue. Principal component analysis of 34 tumor spectra predicts early postoperative cancer recurrence with a sensitivity of 73% and specificity of 74%. Spectral analysis reveals elevated porphyrin levels in the normal samples and more DNA in the tumor samples. Raman microscopy can be a useful technique for the diagnosis and prognosis of lung cancer patients receiving surgery, and for elucidating the biochemical properties of lung tumors. (C) 2010 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3323088]

The use of lytic bacteriophages in the prevention and eradication of biofilms of Proteus mirabilis and Escherichia coli.

Antibiotics have been the cornerstone of the clinical management of bacterial infections since their discovery in the early part of the last century. Eight decades later, their widespread, often indiscriminate use, has resulted in an overall reduction in their effectiveness, with reports of multidrug-resistant bacteria now commonplace. Increasing reliance on indwelling medical devices, which are inherently susceptible to biofilm-mediated infections, has contributed to unacceptably high rates of nosocomial infections, placing a strain on healthcare budgets. This study investigates the use of lytic bacteriophages in the treatment and prevention of biofilms of bacterial species commonly associated with infections of indwelling urological devices and catheter-associated urinary tract infections. The use of lytic bacteriophages against established biofilms of Proteus mirabilis and Escherichia coli is described, whereby biofilm populations have been reduced successfully by three to four log cycles (99.9-99.99% removal). The prevention of biofilm formation on Foley catheter biomaterials following impregnation of hydrogel-coated catheter sections with a lytic bacteriophage has also been investigated. This has revealed an approximate 90% reduction in both P. mirabilis and E. coli biofilm formation on bacteriophage-treated catheters when compared with untreated controls.