The response of macrophages to particles of resorbable polymers and their degradation products

Alpha polyesters such as poly(L-lactide) and poly(glycolide) are biodegradable materials used in fracture fixation and they need to be assessed for problems associated with their degradation products. This study has compared cell responses to low molecular weight poly(L-lactide) particles, lactate monomer, poly(glycolide) particles and glycolic acid at cytotoxic and sub-cytotoxic concentrations. Murine macrophages were cultured in vitro and the release of lactate dehydrogenase (LDH), prostaglandin E-2 (PGE(2)) and interleukin-1 alpha IL-1alpha was measured following the addition of particles or monomer. Experiments revealed that both the poly(L-lactide) and poly(glycolide) particles gave rise to dose dependent increases in LDH release and an increase in IL-1alpha and PGE(2) release. Comparisons of the poly(L-lactide) particles to the poly(glycolide) particles did not reveal any differences in their stimulation of LDH, IL-1alpha and PGE(2) release. The lactate and glycolate monomers did not increase PGE(2) or IL-1alpha release above control levels. There was no difference in biocompatibility between the poly(L-lactide) and poly(glycolide) degradation products both in particulate and monomeric form. (C) 2003 Kluwer Academic Publishers.

Dual functional ionic liquids as plasticisers and antimicrobial agents for medical polymers

Contamination of medical devices with bacteria such as Meticillin resistant Staphylococcus aureus (MRSA) is of great clinical concern. Poly(vinyl chloride) is widely used in the production of medical devices, such as catheters. The flexibility of catheter tubing is derived from the addition of plasticisers. Here, we report the design of two dual functional ionic liquids, 1-ethylpyridinium docusate and tributyl(2-hydroxyethyl)phosphonium docusate, which uniquely provide a plasticising effect, and exhibit antimicrobial and antibiofilm-forming activity to a range of antibiotic resistant bacteria. The plasticisation of poly(vinyl chloride) was tailored as a function of ionic liquid concentration. The effective antimicrobial behaviour of both ionic liquids originates from the chemical structure of the anion or cation and is not limited to the length of the alkyl chain on the anion/cation. The design approach adopted will be useful in developing ionic liquids as multi-functional additives for polymers.

Solving the problem of diffraction of an optical-band electromagnetic wave by metal nanostructured aperture arrays with the use of the method of impedance boundary conditions

The problem of diffraction of an optical wave by a 2D periodic metal aperture array with square, circular, and ring apertures is solved with allowance for the finite permittivity of a metal in the optical band. The correctness of the obtained results is verified through comparison with experimental data. It is shown that the transmission coefficient can be substantially greater than the corresponding value reached in the case of diffraction by a grating in a perfectly conducting screen.

Novel pyridyl-stabilised rigid-rod organometallic polymers and their monomeric precursors

Reaction of trans-[Pt(NC5H4CHBu2n)(2)Cl-2] 1 with an excess of HC=CR (R = Ph, C6H4Me, C6H4NO2) affords the monomeric complex trans-[Pt(NC5H4CHBu2n)(2)(C=CR)(2)] (R = Ph 2a, C6H4Me 2b, C6H4NO2 2c), the trans arrangement of the alkynyl ligands being confirmed from spectroscopic data and by an X-ray analysis of 2c;when 1 is treated with 1 equiv, of HC=CC6H2(Me)(2)C=CH the polymer [Pt(NC5H4CHBu2n)(2)C=CC6H2Me2C=C](n) is formed, which is soluble in a range of organic solvents.

Organometallic polymers: An infinite organoplatinum chain in the solid state formed by (C CH center dot center dot center dot ClPt)hydrogen bonds

The new platinum complex [PtCl[C6H2(CH(2)NMe(2))(2) -2,6-(C=CH)-4)] exhibits a polymeric linear -C=CH ... ClPt-hydrogen-bonded structure in the solid state.

Phase behavior of mixtures of colloidal platelets and nonadsorbing polymers

The phase behavior of a model system of colloidal platelets and nonadsorbing polymers is studied using computer simulations and perturbation theory. The equation of state for the pure platelet reference system is obtained by Monte Carlo simulations, and the free volume fraction accessible to polymers is measured by a trial insertion method. The free volume fraction is also calculated using scaled particle theory. Subsequently, the phase diagram for platelet-polymer mixtures is calculated. For a platelet aspect ratio L/D=0.1 and a polymer to platelet size ratio d/D>0.2, we observe coexistence between two isotropic phases with different densities. For smaller polymers d/D

Textural, viscoelastic and mucoadhesive properties of pharmaceutical gels composed of cellulose polymers

This study examined the mechanical/textural, viscoeiastic and mucoadhesive properties of a range of aqueous gels composed of either hydroxyethylcellulose (HEC) or sodium carboxymethylcellulose (Na CMC). The mechanical/textural properties of each formulation were determined using texture profile analysis. The viscoelastic properties of each formulation were examined over a defined frequency range (0.01-1.0 Hz) using oscillatory rheometry in conjunction with stainless steel parallel plate geometry. The mucoadhesive properties of the gels were evaluated by measuring the tensile force required to overcome the gel/mucin adhesive interaction. Both gel hardness and compressibility, properties that affect the ease of product removal from a container and spreadability, increased as a function of increasing polymer concentrations. This is attributed to the effects of HEC and Na CMC on gel viscosity. Gel adhesiveness, a property related to bioadhesion, also increased as a function of polymer concentration and is attributed to the reported adhesive nature of these polymers. Increasing frequency of oscillation increased the storage and loss moduli yet decreased bath the dynamic viscosity of each gel type and also the loss tangent of HEC (but not Na CMC) gels. Therefore, following exposure to the range of oscillatory stresses that may be expected in vivo, HEC gels will be more susceptible than Na CMC gels to alterations in these rheological properties. Consequently, it would be expected that the clinical performance of HEC gels will be modified to a greater extent than Na CMC gels. In general, HEC gels exhibited a greater elastic nature than Na CMC gels over the frequency range employed for oscillation The storage and loss moduli and dynamic viscosity of both gel types increased, yet the loss tangent of both gel types decreased as a function of increasing polymer concentration. Gel mucoadhesive strength was dependent on both the time of contact of the formulation with mucin and also on polymer concentration. In conclusion, this study has characterised a number of gels containing either HEC or Na CMC in terms of their mechanical/textural, viscoelastic and mucoadhesive properties. Due to its relevance to the clinical performance, it is suggested that the information derived from these methods may be usefully combined to provide a more rational basis for the selection of polymers and their formulation as topical drug delivery systems. (C) 1997 Elsevier Science B.V.