Delivery systems made of natural-origin polymers for tissue engineering and regenerative medicine applications

There is an emergent need in the development of more specific and effective therapeutic agent carriers to help on the regeneration of a plethora of tissues. The ultimate aim of bioactive factors delivery systems development is to improve the human health with the fewest possible adverse reactions. While there have been many polymeric scaffolds and matrices with different forms and compositions developed to load and deliver bioactive factors, the delivery strategy should be established based on the type of molecules to deliver and mechanisms to control their release. As most bioactive factors such as proteins and genes are water-soluble, natural polymers are more favored than synthetic ones for this purpose. A core-shell structuring of biomaterials (in the cases of particles or fibers) where water-based polymers being placed in the inner core part may be the most common design principal to secure bioactive factors during the processing of synthetic drug delivery scaffolds.(undefined)info:eu-repo/semantics/submittedVersio

Fabrication of Biomaterials via Controlled Protein Bubble Generation and Manipulation

In this work, we utilize a recently developed microbubbling process to generate controlled protein (bovine serum albumin, BSA) coated bubbles and then manipulate these to fabricate a variety of structures suitable for several generic biomedical applications, tissue engineering, and biosensor coatings. Using BSA solutions with varying concentrations (20, 25, and 30 wt%) and cross-linking (terephthaloyl chloride) mechanisms, structures were fabricated including porous thin films with variable pore sizes and thickness (partially cross-linked coupled to bubble breakdown), scaffolds with variable pore morphologies (fully cross-linked), and coated bubbles (no cross-linking), which can be used as stand-alone delivery devices and contrast agents. The movement of typical biosensor chemicals (catechol and hydrogen peroxide) across appropriate film structures was studied. The potential of formed scaffold structures for tissue engineering applications was demonstrated using mouse cell lines (L929). In addition to low cost, providing uniform structure generation and high output, the size of the bubbles can easily be controlled by adjusting simplistic processing parameters. The combination of robust processing and chemical modification to uniform macromolecule bubbles can be utilized as a competing, yet novel, tool with current technologies and processes in advancing the biomaterials and biomedical engineering remits

Chitosan microparticles as injectable scaffolds for tissue engineering

The use of chitosan microparticles as injectable carriers for cell transplantation represents a promising alternative to avoid the drawbacks of the implantation of other forms of three-dimensional (3D) scaffolds seeded with cells. In this study, a 3D construct is obtained in vitro by combining chitosan microparticles crosslinked with genipin and goat bone marrow stromal cells (GBMCs). Cell viability and the morphology of GBMCs were evaluated after culture for 7 and 14 days. Our results show the feasibility of chitosan microparticles as potential injectable scaffolds for tissue engineering and regenerative medicine.Support from the Generalitat Valenciana through a short-term fellowship (No. BEFPI/2007/012) is kindly acknowledged. D.M.G.C. and J.L.G.R. acknowledge the support of the Spanish Ministry of Science through Project No. MAT2007-66759-C03-01 (including FEDER financial support). This work was also partially supported by the European Union-funded STREP Project HIPPOCRATES (NMP3-CT-2003-505758), and the European NoE EXPERTISSUES (NMP3-CT-2004-500283)

Tuberculosis chemotherapy: current drug delivery approaches

Tuberculosis is a leading killer of young adults worldwide and the global scourge of multi-drug resistant tuberculosis is reaching epidemic proportions. It is endemic in most developing countries and resurgent in developed and developing countries with high rates of human immunodeficiency virus infection. This article reviews the current situation in terms of drug delivery approaches for tuberculosis chemotherapy. A number of novel implant-, microparticulate-, and various other carrier-based drug delivery systems incorporating the principal anti-tuberculosis agents have been fabricated that either target the site of tuberculosis infection or reduce the dosing frequency with the aim of improving patient outcomes. These developments in drug delivery represent attractive options with significant merit, however, there is a requisite to manufacture an oral system, which directly addresses issues of unacceptable rifampicin bioavailability in fixed-dose combinations. This is fostered by the need to deliver medications to patients more efficiently and with fewer side effects, especially in developing countries. The fabrication of a polymeric once-daily oral multiparticulate fixed-dose combination of the principal anti-tuberculosis drugs, which attains segregated delivery of rifampicin and isoniazid for improved rifampicin bioavailability, could be a step in the right direction in addressing issues of treatment failure due to patient non-compliance

Investigation of temperature sensitivity behaviors of water soluble polyacrylamides

Temperature sensitive polymers with a lower critical solution temperature (LCST) are used in a variety of industries such as the pharmaceutical, cosmetic, food, and paint. These polymers are generally of the poly(N-alkylacrylamide) type, of which poly(N-isopropylacrylamide) (PNIPA) is the most commonly used. More novel poly(N-alkylacrylamide)s have also been the subject of much attention recently. In this study, N-alkylacrylamides containing different alkyl groups were synthesized by nucleophylic substitution reactions of various amines with acryloyl chloride. They were polymerized using the solution polymerization method, and the temperature sensitivities of the polymers were investigated. For this purpose, three monomers, N,N-diethylacrylamide, N-cyclopropylacrylamide, and 4-piperidineethanolacrylamide, were synthesized using diethylamine, cyclopropylamine, and 4-piperidineethanol, as the amines, respectively. The obtained polymers, poly(N,N-diethylacrylamide) (PDEA), poly(N- cyclopropylacrylamide) (PCPA), and poly(4-piperidineethanolacrylamide) (PPEA), were found to be thermoresponsive, particularly PPEA is a potential novel material that can be utilized as an alternative to the common temperature sensitive polymers. The effects of several conditions on the LCST and the critical flocculation temperature (CFT) of the polymers were also investigated. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 Copyright © 2012 Wiley Periodicals, Inc

Chitosan microspheres and sponges: Preparation and characterization

In this study, chitosan microspheres and sponges were prepared and characterized for diverse biomedical applications successfully. The chitosan microspheres were obtained with a "suspension crosslinking technique" in the size range of 30-700 mu m. The stirring rate of the suspension medium and the chitosan/acetic acid ratio, emulsifier, and crosslinker, that is, the glutaraldehyde concentration in the suspension medium, were evaluated as the effective parameters on the size/size distributions of the microspheres. The microsphere size/size distributions were increased with the decreasing of all effective parameters except the chitosan/acetic acid ratio. In the second part of the study, chitosan sponges were prepared with a solvent-evaporation technique and sponges were cross-linked either during the formation or after the formation of sponges by using a cross-linker, that is, glutaraldehyde. When the sponges were crosslinked during the formation, fibrillar structures were obtained, while the leaflet structures were obtained in the case of crosslinking after the formation of sponges. In the last part of the study, the swelling behavior of both the chitosan microspheres and sponges were evaluated using different amounts of the crosslinker. The swelling ratio was increased in both types of structures, that is microspheres and sponges, by decreasing the amount of the crosslinker. (C) 2000 John Wiley & Sons, Inc