Preparation of ultrafine poly(methyl methacrylate-co-methacrylic acid) biodegradable nanoparticles loaded with ibuprofen

Loading of doxorubicin on poly(methyl methacrylate-co-methacrylic acid) nanoparticles and release study

Nanoparticles (NP) of 12.7 nm in diameter of the poly(methyl methacrylate (MMA)-co-methacrylic acid (MAA)) copolymer were prepared. ¹³C-NMR results showed a MMA:MAA molar ratio of 0.64:0.36 in the copolymer, which is similar to the poly(MMA-co-MAA) commercially known as the FDA approved Eudragit S100 (0.67:0.33). The NP prepared in this study were loaded at pH 5 with varying amounts (from 0.54 to 6.91%) of doxorubicin (DOX), an antineoplastic drug. ¹H-NMR results indicated the electrostatic interactions between the ionized carboxylic groups of the MAA units in the copolymer and the proton of the glycosidic amine in DOX. Measurements by QLS and TEM indicated that the loading destabilizes the NP, and that for increase stability, they aggregate in a reversible way, forming aggregates with a diameter up to 99.5 nm at a DOX load of 6.91%. The analysis of drug release data at pH 7.4 showed that loaded NP with at least 4.38% DOX release the drug very slowly and follows the Higuchi model; the former suggests that they could remain for long periods in the bloodstream to reach and destroy cancer cells.

Characterization of Initial Cell Adhesion on Charged Polymer Substrates in Serum-Containing and Serum-Free Media

Charged substrates are expected to promote cell adhesion via electrostatic interaction, but it remains unclear how cells adhere to these substrates. Here, initial cell adhesion (<30 min) was re-examined on charged substrates in serum-containing and serum-free media to distinguish among various cell adhesion mechanisms (i.e., electrostatic interaction, hydrophobic interaction, and biological interaction). Cationic and anionic methacrylate copolymers were coated on nonionic nontissue culture-treated polystyrene to create charged substrates. Cells adhered similarly on cationic, anionic, and nonionic substrates in serum-free medium via integrin-independent mechanisms, but their adhesion forces differed (anionic > cationic > nonionic substrates), indicating that cell adhesion is not mediated solely by the cells' negative charge. In serum-containing medium, the cells adhered minimally on anionic and nonionic substrates, but they adhered abundantly on cationic substrates via both integrin-dependent and -independent mechanisms. These results suggest that neither electrostatic force nor protein adsorption is accountable for cell adhesion. Conclusively, the observed phenomena revealed a gap in the generally accepted understanding of cell adhesion mechanisms on charged polymeric substrates. A reanalysis of their mechanisms is necessary.

Prevention of encrustation and blockage of urinary catheters by Proteus mirabilis via pH-triggered release of bacteriophage

The crystalline biofilms of Proteus mirabilis can seriously complicate the care of patients undergoing long-term indwelling urinary catheterisation. Expression of bacterial urease causes a significant increase in urinary pH, leading to the supersaturation and precipitation of struvite and apatite crystals. These crystals become lodged within the biofilm, resulting in the blockage of urine flow through the catheter. Here, we describe an infection-responsive surface coating for urinary catheters, which releases a therapeutic dose of bacteriophage in response to elevated urinary pH, in order to delay catheter blockage. The coating employs a dual-layered system comprising of a lower hydrogel 'reservoir' layer impregnated with bacteriophage, capped by a 'trigger' layer of the pH-responsive polymer poly(methyl methacrylate-co-methacrylic acid) (EUDRAGIT®S 100). Evaluation of prototype coatings using a clinically reflective in vitro bladder model system showed that catheter blockage time was doubled (13 h to 26 h (P < 0.05)) under conditions of established infection (10⁸ CFU ml^-1) in response to a 'burst-release' of bacteriophage (10⁸ PFU ml^-1). Coatings were stable both in the absence of infection, and in the presence of urease-negative bacteria. Quantitative and visual analysis of crystalline biofilm reduction show that bacteriophage constitute a promising strategy for the prevention of catheter blockage, a clinical problem for which there is currently no effective control method.

Biocompatible and Biodegradable Ultrafine Nanoparticles of Poly(Methyl Methacrylate-co-Methacrylic Acid) Prepared via Semicontinuous Heterophase Polymerization: Kinetics and Product Characterization

Ultrafine nanoparticles, less than 10 nm in mean diameter, of the FDA approved copolymer methyl methacrylate- (MMA-)co-methacrylic acid (MAA), 2/1 (mol/mol), were prepared. The method used for the preparation of these particles stabilized in a latex containing around 11% solids includes the dosing of the monomers mixture on a micellar solution preserving monomer starved conditions. It is thought that the operation at these conditions combined with the hydrophilicity of MMA and MAA units favors the formation of ultrafine particles; the propagation reaction carried out within so small compartments renders copolymer chains rich in syndiotactic units very likely as consequence of the restricted movements of the end propagation of the chains. Because of their biocompatibility and biodegradability as well as their extremely small size these nanoparticles could be used as vehicles for improved drug delivery in the treatment of chronic-degenerative diseases.