Biomaterials synthetic modifications

Synthetic modifications onto biomaterials are to be carried out as follows. 

A comprehensive review of radiation techniques in the formulation of synthetic biomaterials was published by Kaetsu.260 Substrate modification by electron beam was discussed by Wendrinsky at RadTech Europe 2001.261... 

Abstract Carbohydrates have been investigated and developed as delivery vehicles for shuttling nucleic acids into cells. In this review, we present the state of the art in carbohydrate-based polymeric vehicles for nucleic acid delivery, with the focus on the recent successes in preclinical models, both in vitro and in vivo. Polymeric scaffolds based on the natural polysaccharides chitosan, hyaluronan, pullulan, dextran, and schizophyllan each have unique properties and potential for modification, and these results are discussed with the focus on facile synthetic routes and favorable performance in biological systems. Many of these carbohydrates have been used to develop alternative types of biomaterials for nucleic acid delivery to typical polyplexes, and these novel materials are discussed. Also presented are polymeric vehicles that incorporate copolymerized carbohydrates into polymer backbones based on polyethylenimine and polylysine and their effect on transfection and biocompatibility. Unique scaffolds, such as clusters and polymers based on cyclodextrin (CD), are also discussed, with the focus on recent successes in vivo and in the clinic. These results are presented with the emphasis on the role of carbohydrate and charge on transfection. Use of carbohydrates as molecular recognition ligands for cell-type specific dehvery is also briefly... 

In spite of recent developments and research in synthetic polymers applied in pharmaceutical field, biomaterials, particularly polysaccharides like starch, cellulose, gums and mucilages, have a greater role to play in pharmaceutical formulation development. It is concluded from the discussion in this entry that because of some limitations at the molecular level, there is a need to modify the parent structure of starch to make it available for pharmaceutical and other industrial uses. Physically and chemically modified starches showed very promising results in the delivery of therapeutic agents. The modified starches have enormous potential to be used in drug delivery because of its easy modification and biodegradability. 

A wide variety of natural and synthetic materials have been used for biomedical applications. These include polymers, ceramics, metals, carbons, natural tissues, and composite materials (1). Of these materials, polymers remain the most widely used biomaterials. Polymeric materials have several advantages which make them very attractive as biomaterials (2). They include their versatility, physical properties, ability to be fabricated into various shapes and structures, and ease in surface modification. The long-term use of polymeric biomaterials in blood is limited by surface-induced thrombosis and biomaterial-associated infections (3,4). Thrombus formation on biomaterial surface is initiated by plasma protein adsorption followed by adhesion and activation of platelets (5,6). Biomaterial-associated infections occur as a result of the adhesion of bacteria onto the surface (7). The biomaterial surface provides a site for bacterial attachment and proliferation. Adherent bacteria are covered by a biofilm which supports bacterial growth while protecting them from antibodies, phagocytes, and antibiotics (8). Infections of vascular grafts, for instance, are usually associated with Pseudomonas aeruginosa Escherichia coli. Staphylococcus aureus, and Staphyloccocus epidermidis (9). 

Synthetic polymers make up by far the broadest and most diverse class of biomaterials This is mainly because synthetic polymers are available with such a wide variety of compositions and properties and also because they may be fabricated readily into complex shapes and structures. In addition, their surfaces may be readily modified physically, chemically, or biochemically. Such modifications can have significant influences on biologic responses to the biomaterials. When a foreign biomaterial contacts blood or tissue fluids, the first measurable response in the initial seconds to... 

In summary, aliphatic polyesters, already an important class of synthetic degradable polymeric biomaterials, have been taken to unprecedented levels of synthetic diversity and tailoring through the efforts of many research groups in the U.S. and abroad. Some of these have been described in this brief review, with a focus on pendent or graft functionality by polymerization of functionalized lactones, and post-polymerization modification. Future efforts in this area must attempt to connect these synthetic advances to specific applications, through the collaborative efforts of experts in the chemistry, biology, and clinical use of synthetic polymer materials. 

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