Macromolecules biodegradation

F. Kawai, Macromol. Symp. 123 (37th Microsymposium on Macromolecules, Biodegradable Polymers Chemical, Biological and Environmental Aspects, 1996)... 

Probably the most promising polymeric drug carrier system involves polysaccharide molecules. These are natural polymers and are often biodegradable to products that are useful to the host or easily eliminated by the host. Dextrans have been the most extensively used polysaccharide for macromolecular prodrug preparations (79). These materials are biocompatible and the in vivo fate is directly related to their molecular weight. Moreover these macromolecules can be easily targetted to the hepatocytes with D-mannose or L-fucose (20). 

Y Doi, Y Kanesawa, M Kunioka, T Saito. Biodegradation of microbial copolyesters Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate). Macromolecules 23 26-31, 1990. 

The biodegradation of macromolecules generally comprises a number of steps that can proceed at different sites from the perspective of the active microorganism. The macromolecule can be taken up into the cell, where it is cut down and further metabolised. Alternatively, the splitting of the macromolecule can be done outside the cell, and the small degradation products then transported into the cell. 

Lofgren A, Albertsson A-C, Dubois P, Jerome R, Teyssie P (1994) Synthesis and characterization of biodegradable homopolymers and block copolymers based on l,5-dioxepan-2-one. Macromolecules 27 5556-5562... 

Shirahama H, Shomi M, Sakane M, Yasuda H (1996) Biodegradation of novel optically active polyesters synthesized by copolymerization of (R)-MOHEL with lactone. Macromolecules 29 4821 828... 

Latere J-P, Lecomte P, Dubois P, Jerome R (2002) 2-Oxepane-l,5-dione a precursor of a novel class of versatile semicrystalline biodegradable (co)polyesters. Macromolecules 21 7857-7859... 

Biodegradable polymers are macromolecules mainly derived from renewable sources, which can be enzymatically or hydrolytically degraded into low molecular parts. These parts can be reabsorbed by microorganisms, which ideally convert them to CO2 and water heading to an environmentally closed circular flow economy between growing of nutrients, production, utilization, and material recycling (Fig. 1). 

Macromolecules as drug carriers may be divided into degradable and nondegradable types based on their fate within the organism. Biodegradable polymeric drug carriers are traditionally derived from natural products polysaccharides, poly(amino acids) in the hope that the body s natural catabolic mechanisms will act to break down the macromolecular structure into small,... 

Triethanolamine is rapidly absorbed and excreted in rodent urine (about 60%) and faeces (about 20%), mainly in the unchanged form. Biodegradation of triethanolamine to monoethanolamine or diethanolamine or to any other putative metabolite has not been shown in rodents, nor has its incorporation into endogenous macromolecules. There is no evidence for formation of A-nitrosodiethanolamine from triethanolamine under physiological conditions. 

Shuai X, Merdan T, Unger F et al (2003) Novel biodegradable ternary copolymers hy-PEI-g-PCL-b-PEG synthesis, characterization, and potential as efficient nonviral gene delivery vectors. Macromolecules 36 5751-5759... 

Two types of side group structures attached to a phosphazene ring or chain induce hydrolytic breakdown — amino acid ester and imidazole residues. The former decompose to alcohol, amino acid, phosphate, and ammonia (10). Hexakis(imidazolyl)cyclo-triphosphazene hydrolyzes rapidly in the pH range 6.5 to 7.8 by a mechanism that involves autocatalysis by the free imidazole liberated. Thus, either type of side group could facilitate biodegradation of chemotherapeutic carrier macromolecules. 

Dendrimers are three-dimensional hyperbranched, globular macromolecules that are capable of condensing DNA into small complexes, and thereby increase plasmid transfection efficiency (14). Dendrimers are typically stable in serum and not temperature sensitive, but are also non-biodegradable and cause significant cytotoxicity. 

There are pyridine cross-links between the parallel chains of collagen of bone mass, namely, between the lysine amino acid residues (PYD), and between the lysine and hydroxylysine residues (DPD). They are found in nonhelical terminal (N- and C-terminal) regions of collagen macromolecules—telopeptides. They are the final products of the biodegradation of collagen excreted to urine in the kidneys. 

The most fundamental classification of polymers is whether they are naturally occurring or synthetic. Common natural polymers (often referred to as biopolymers) include macromolecules such as polysaccharides e.g., starches, sugars, cellulose, gums, etc.), proteins e.g., enzymes), fibers e.g., wool, silk, cotton), polyisoprenes e.g., natural rubber), and nucleic acids e.g., RNA, DNA). The synthesis of biodegradable polymers from natural biopolymer sources is an area of increasing interest, due to dwindling world petroleum supplies and disposal concerns. 

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