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The aim of the present work was to study the possibility of building a porous scaffold for tissue engineering with a new bottom-up approach, obtained by assembling two-dimensional-micro, one-dimensional-nano sized poly(L-lactide) lamellar single crystals. This choice was dictated by the fact that polymer single crystals have structural and morphological features which can be exploited for chemical surface modifications to give a system characterized by a high specific active surface area. Indeed, the outermost amorphous regions can undergo functionalization reactions easily, whereas the inner, relatively inaccessible and inert crystalline core ensures morphological and mechanical stability. The assembling method employed to give the porous structures is based on a mould pressing, salt leaching technique and was found to be facile and versatile. In the first part of this paper we report the experimental results obtained to find the best conditions to achieve a suitable frame in terms of morphology, porosity and mechanical properties. In the second part of the paper, we describe the biological tests performed by using mouse fibroblasts seeded onto scaffolds prepared from pristine and surface hydrolysed lamellae. The results show that the samples obtained are suitable for sustaining cells which can proliferate and reach the inner pores of the scaffold containing hydrolysed single crystals much better than those prepared from pristine lamellae. Copyright (c) 2012 Society of Chemical Industr

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Usnic acid, a potent antimicrobial and anticancer agent, poorly soluble in water, was complexed to novel antimicrobial polyacrylamides by establishment of strong acidic-base interactions. Thermal and spectroscopic analysis evidenced a molecular dispersion of the drug in the polymers and a complete drug/polymer miscibility for all the tested compositions. The polymer/drug complexes promptly dissolved in water and possessed a greater antimicrobial activity against Staphylococcus epidermidis than both the free drug and the polymer alone. The best results were obtained with the complex based on the lowest molecular weight polymer and containing a low drug content. Such a complex showed a larger inhibition zone of bacterial growth and a lower minimum inhibitory concentration (MIC) with respect to usnic acid alone. This improved killing effect is presumably due to the reduced size of the complexes that allows an efficient cellular uptake of the antimicrobial complexes. The killing effect extent seems to be not significantly dependent on usnic acid content in the samples.

The toluidine blue (TB) aggregation phenomenon in water solutions was investigated by UV-Vis absorption spectroscopy in a wide range of concentrations, from 10−9 to 10−2 M. The experimental data were fitted by assuming that the spectrum was due to the overlapping of the bands of six different aggregation species simultaneously present in solution. The model and the peak centres of the different species were hypothesized on the basis of exciton theory. All the spectra obtained were simultaneously processed thus allowing the derivation of the K constant, which was assumed to be the same for all the equilibria and which was found equal to 10 500. The ε spectra of the different aggregation species were also obtained. The overall TB spectrum may be mainly attributed to the H-type aggregation, although some of the species also show the J type bands. The structural features of TB and its dimeric aggregate were also investigated by means of molecular mechanics semi-empirical potential energy calculations. The results obtained for the dimer confirm the H type aggregation and show that the lowest energy model of the four possible is the one obtained by a mirror plane of symmetry containing the aromatic rings, in agreement with the x-ray diffraction data which will be presented in a forthcoming paper.

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Poly(L‐lactide) (PLLA) single crystals grown from dilute solution were employed for the first time in the preparation of drug delivery systems. PLLA single crystals were selectively hydrolyzed with HCl to provide the lamellar surface with carboxylic groups, which were employed to graft Dipyridamole (Dip), chosen as a model drug. The influence of the hydrolysis conditions on the single crystals properties was investigated by FT‐IR, DSC and GPC measurements, while Dip grafting yield and drug release in lipase solution were followed by UV‐vis spectroscopy. Dip was slowly delivered over a few days, suggesting the potential use of PLLA single crystals as controlled drug release carriers for either oral or parenteral injection administration.magnified image

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