Anna Maria Piras

Micro/nanostructured polymeric systems for biomedical and pharmaceutical applications

This review provides an outline of the polymeric micro/nanostructured advanced systems that are suited for the controlled and targeted administration of, specifically, nonconventional drugs. The contribution of new trends in drug-delivery technology is focused on two major parts, dealing with brief surveys of: the biodegradable/bioerodible polymeric systems used in the formulation of micro/nanoparticles and techniques used in the preparation of micro/nanoparticles for their biomedical application in cancer treatment specifically, in inflammation pathologies, as oxygen carriers (blood substitutes) and in tissue-engineering practice. A small discussion of the future perspectives of the described systems is also given.

Novel agmatine-containing poly(amidoamine) hydrogels as scaffolds for tissue engineering

Novel biocompatible and biodegradable amphoteric poly(amidoamine) (PAA) hydrogels were designed for applications as scaffolds for tissue engineering. These hydrogels (PAA-AG1 and PAA-AG2) were obtained by polyaddition of 2,2-bisacrylamidoacetic acid with 2-methylpiperazine and 4-aminobutyl guanidine, a bioactive molecule with a known ability to induce adhesion to cell membranes. They contain carboxylic functions in their main chain and interchain connections deriving from two different cross-linking agents: for PAA-AG1, a multifunctional primary amine, that is, 1,10-decanediamine; for PAA-AG2, a purposely synthesized PAA (PAA-NH(2)) containing pendant NH(2). Both PAA-AG1 and PAA-AG2 proved noncytotoxic and adhesive to cell membranes, as ascertained by means of cytotoxicity and proliferation tests carried out on fibroblast cell lines. Good apparent mechanical strength was also observed in the case of PAA-AG2, cross-linked with the PAA-NH(2). Both PAA-AG1 and PAA-AG2 underwent degradation tests under controlled conditions simulating the biological environments, that is, Dulbecco medium at pH 7.4 and 37 degrees C. They completely dissolved within 10 and about 40 days, respectively. In both cases, the degradation products were completely noncytotoxic. All the results of this paper point to the conclusion that agmatine-based PAA hydrogels are excellent substrates for cell proliferation.

A new biocompatible nanoparticle delivery system for the release of fibrinolytic drugs

The preparation of novel biocompatible polymeric nanoconstructs suitable to load sensitive bioactive protein agents is reported. Nanoparticles were prepared as based on hybrid polymeric matrices consisting of synthetic bioerodible alternating copolymers of maleic anhydride and n-butylvinylether hemiesterified with 2-methoxyethanol and grafted with poly(ethylene glycol) segments and monoclonal antibody single chain fragment specific for fibrin clot. The prepared nanoparticles were loaded with proteolytic enzymes (trypsin and urokinase), encapsulating up to 2500UI of urokinase/mg of dried nanoparticles. The release of the enzyme from nanoparticles resulted time controlled and it was assessed that in case of administration of urokinase-loaded nanoparticles, the enzyme would preserve its thrombolytic properties more efficiently in respect to free drug administration. Moreover, the nanoparticles showed a good in vitro biocompatibility, suitable for biomedical applications. The stability (shelf life) of the prepared nanostructured dosage forms was evaluated. The drug-loaded nanoparticles resulted stable under stressed conditions (35 degrees C for 13 weeks) in a lyophilized form and preserved their morphological and functional characteristics when stored in suspension for 18 months at 4 degrees C.

Chitosan nanoparticles loaded with the antimicrobial peptide temporin B exert a long-term antibacterial activity in vitro against clinical isolates of Staphylococcus epidermidis

Nowadays, the alarming rise in multidrug-resistant microorganisms urgently demands for suitable alternatives to current antibiotics. In this regard, antimicrobial peptides (AMPs) have received growing interest due to their broad spectrum of activities, potent antimicrobial properties, unique mechanisms of action, and low tendency to induce resistance. However, their pharmaceutical development is hampered by potential toxicity, relatively low stability and manufacturing costs. In the present study, we tested the hypothesis that the encapsulation of the frog-skin derived AMP temporin B (TB) into chitosan nanoparticles (CS-NPs) could increase peptide’s antibacterial activity, while reducing its toxic potential. TB-loaded CS-NPs with good dimensional features were prepared, based on the ionotropic gelation between CS and sodium tripolyphosphate. The encapsulation efficiency of TB in the formulation was up to 75%. Release kinetic studies highlighted a linear release of the peptide from the nanocarrier, in the adopted experimental conditions. Interestingly, the encapsulation of TB in CS-NPs demonstrated to reduce significantly the peptide’s cytotoxicity against mammalian cells. Additionally, the nanocarrier evidenced a sustained antibacterial action against various strains of Staphylococcus epidermidis for at least 4 days, with up to 4-log reduction in the number of viable bacteria compared to plain CS-NPs at the end of the observational period. Of note, the antimicrobial evaluation tests demonstrated that while the intrinsic antimicrobial activity of CS ensured a “burst” effect, the gradual release of TB further reduced the viable bacterial count, preventing the regrowth of the residual cells and ensuring a long-lasting antibacterial effect. The developed nanocarrier is eligible for the administration of several AMPs of therapeutic interest with physical–chemical characteristics analog to those of TB.

Poly(vinyl alcohol)-based electrospun meshes as potential candidate scaffolds in regenerative medicine

Fibrous meshes based on three different poly(vinyl alcohol) (PVA) polymers, with 12% vinyl acetate monomeric units and molar weights of 37,000, 67,000, and 130,000 were developed as potential scaffolds for regenerative medical applications. The meshes were electrospun and characterized by molecular weight, concentration, applied voltage, and needle—collector distance. The influence of feed rate and the electrodes configuration (needle-to-tip and screen-to-screen system) was determined. Highly porous, 3D structures composed of randomly oriented ultrafine fibers, with an average fiber diameter of a few hundred nanometers were developed. Solutions of PVA and human serum albumin were successfully electrospun and the fibrous mesh was stabilized with glutaraldehyde. The influence of these operations on the mechanical properties was evaluated by uniaxial tensile testing.

Polymeric nanoparticles for hemoglobin-based oxygen carriers.

This article reports on the current status of the research on blood substitutes with particular attention on hemoglobin-based oxygen carriers (HBOCs). Insights on the physiological role of hemoglobin are reported in the view of the development of both acellular and cellular hemoglobin-based oxygen carriers. Attention is then focused on biocompatible polymeric materials that find application as matrices for cellular based HBOCs and on the strategies employed to avoid methemoglobin formation. Results are reported regarding the use of bioerodible polymeric matrices based on hemiesters of alternating copolymer (maleic anhydride-co-butyl vinyl ether) for the preparation of hemoglobin loaded nanoparticles.

Fibrin acts as biomimetic niche inducing both differentiation and stem cell marker expression of early human endothelial progenitor cells

Objectives:  Transplantation of endothelial progenitor cells (EPCs) is a promising approach for revascularization of tissue. We have used a natural and biocompatible biopolymer, fibrin, to induce cell population growth, differentiation and functional activity of EPCs.

Development of Electrospun Three-arm Star Poly(ε-caprolactone) Meshes for Tissue Engineering Applications

We have developed three-dimensional electrospun microfibrous meshes of a novel star branched three-arm poly(ε-caprolactone) (*PCL) as potential scaffolds for tissue engineering applications. The processing conditions required to obtain uniform fibers were optimized by studying their influence on fiber morphology and size. Polymer molecular weight and solution feed rate influenced both the mesh microstructure and the tensile properties of the developed mats. Electrospun samples were also tested for their mechanical properties in wet conditions, showing higher yield strength and strain in comparison to that observed in dry conditions. Cell culture experiments employing MC3T3-E1 osteoblast like cells showed good cell viability adhesion and collagen production on the *PCL scaffolds.

New Multicomponent Bioerodible Electrospun Nanofibers for Dual-controlled Drug Release

The objective of this study was to evaluate the bioerodible polymer poly(maleic anhydride-alt-2-methoxyethyl vinyl ether) n-butyl hemiester, for multicomponent drug-loaded nanofibers produced by electrospinning. Diclofenac sodium (DS) and human serum albumin (HSA) were used as conventional drug and biopharmaceutical models. The influence of drug loading was correlated to beads presence, morphology and fibers diameter. When DS and HSA were loaded separately, a uniform distribution within fibers and beads was observed. However, when both components were loaded simultaneously, a heterogeneous distribution of DS was observed with a prominent amount in the cylindrical beads. The in vitro drug release evaluation from these nanomaterials displayed an independent delivery of the two components. These studies support the feasibility of multicomponent, bioerodible polymeric nanofibers preparation loaded with combination of traditional drugs and proteins.

Preparation, physical-chemical and biological characterization of chitosan nanoparticles loaded with lysozyme.

A commercially available chitosan (CS) was employed in the formulation of nanoparticles loaded with lysozyme (LZ) as antimicrobial protein drug model. Due to the variability of commercially available batches of chitosans and to the strict dependence of their physical and biological properties to the molecular weight (Mw) and deacetylation degree (DD) of the material, the CS was fully characterized resulting in weight-average molecular weight of 108,120g/mol and DD of 92%. LZ-loaded nanoparticles (LZ-NPs) of 150nm diameter were prepared by inotropic gelation. The nanoparticles were effectively preserving the antibacterial activity of the loaded enzyme, which was slowly released over 3 weeks in vitro and remained active toward Staphylococcus epidermidis up to 5 days of incubation. Beyond the intrinsic antibacterial activity of CS and LZ, the LZ-NPs evidenced a sustained antibacterial activity that resulted in about 2 log reduction of the number of viable S. epidermidis compared to plain CS nanoparticles. Furthermore, the LZ-NPs showed a full in vitro cytocompatibility toward murine fibroblasts and, in addition to the potential antimicrobial applications of the developed system, the proposed study could serve as an optimal model for development of CS nanoparticles carrying antimicrobial peptides for biomedical applications.