Polyurethane-based microparticles: Formulation and influence of processes variables on its characteristics

Sodium Alginate as a Pharmaceutical Excipient: Novel Applications of a Well-known Polymer

Alginates are naturally occurring polymers revealing low toxicity, good biocompatibility and biodegradability, excellent gelling and thickening properties, as well as low production cost and good availability. One of the most important features typical for alginates is the ability to undergo ionotropic gelation which is gel formation process occurring upon the contact with cations. Because of their advantageous properties, alginates have been extensively utilized in food and pharmaceutical industries. In this review the current knowledge regarding the most recent studies involving both popularly applied dosage forms, like tablets or hydrogels, and novel advanced drug delivery systems applied in targeted therapies are summarized and discussed. The presented studies indicate that although sodium alginate is a well-established polymer, it is still widely applied as pharmaceutical excipient and the presented research studies indicate that there are still research areas that can be explored and provide innovation in drug delivery systems.

Synthesis and in vitro characterization of poly(ethylene glycol)-albumin hydrogel microparticles

High water content hydrogel microparticles based on the cross-linking of albumin with activated poly(ethylene glycol) were synthesized. The influence of different synthesis parameters on the physicochemical characteristics of the microparticles, such as the type of oil and of albumin, and the molecular weight of PEG, was evaluated. The water content of the microparticles ranged from 95 to 98%, increasing with an increase of the molecular weight of PEG. At optimal conditions, microparticles with sizes ranging from 3 to 50 μm were prepared. These microparticles showed a negatively charged surface. They were freely dispersed in PBS buffer and they were stable at 4°C for times varying from 0.5 to 10 months. Initial stirring speed and molecular weight of PEG were the 2 main factors that significantly affected microparticle size. High hydrophilicity, good stability and modulable size make this hydrogel an attractive matrix for protein or cell immobilization for biomedical applications.

Biological relevance of ion energy in performance of human endothelial cells on ion-implanted flexible polyurethane surfaces

To improve the biocompatibility of polyurethane (PUR), we modified the surface by irradiation with different ions (Carbon; C, Oxygen; O, Nitrogen; N, or Argon; Ar) at 0.3-50 keV energy and doses of 1,00E+13 - 1,00E+15 ions/cm(2). The effects of ion implantation using different ion energies and densities were observed on adhesion, proliferation, and viability of human umbilical vein endothelial cells (HUVECs). The long-term in vitro stability of ion-implanted PUR was also investigated. Ion irradiation moderately affected the surface roughness (R(a)), but strongly enhanced the work of adhesion (W(a)). Cell adhesion was markedly improved on O-, N-, and Ar-, but not on C-implanted PUR surfaces. Medium ion energies and lower ion doses produced the best HUVEC attachment and proliferation, indicating the importance of choosing the proper range of energy applied during ion irradiation. In addition, apoptosis rates were significantly reduced when compared with unmodified PUR (uPUR). N implantation significantly protected the surface, although C implantation led to stronger surface erosions than on uPUR. In total, ion implantation on flexible PUR surfaces strongly improved the material surface characteristics and biocompatibility. Electron beam ion implantation within an appropriate energy window is thus a key to improving flexible PUR surfaces for clinical use to support endothelial cell performance. Thus, it can contribute to designing small-diameter grafts, which are in great demand, towards vascular tissue engineering applications.