How are polyanhydrides degraded?
They erode layer by layer, like a lollipop. The hydrophobic backbone with hydrolytically labile anhydride linkages allows hydrolytic degradation to be controlled by manipulating the polymer composition. This manipulation can occur by adding a hydrophilic group to the polyanhydride to make a copolymer.
How is Polyanhydride synthesized?
Polyanhydride polymers are synthesized by dehydrating dicarboxylic acid functional monomers to form corresponding polyanhydride linkages (Figure 7). The anhydride groups in the polymer chain are very moisture sensitive and on contact with water rapidly hydrolyze to form carboxylic acid groups.
Is insulin chemically stable?
The effect of the physical state of the insulin on the chemical stability was also complex, suggesting an intricate dependence of intermolecular proximity of involved functional groups. At pH values below five and above eight, insulin degrades relatively fast.
What is protein glycation?
Glycation is a nonenzymatic chemical reaction whereby sulfhydryl protein linkages are replaced by glucose, causing impairment in normal cellular and tissue functions.
What are polyanhydrides used for?
Polyanhydrides find uses in the medical device and in the pharmaceutical industry. They are used as controlled-release coatings for drug delivery systems to control the rate of release of an active ingredient.
What is modification of insulin?
Chemical modifications found in insulin preparations include covalent dimer formation, deamidation of the C-terminal asparagine in the A-chain (Asn A21), deamidation of Asn B3, and hydrolysis of the peptide bond between residues A8 and A9 (Fig. 1 ▶; Brange et al. 1992).
Is NPH modified insulin?
This new modified protamine insulin is an “intermediate insulin,” with a duration of action longer than that of unmodified (crystalline or regular) but shorter than that of protamine zinc insulin. NPH insulin, however, resembles protamine zinc insulin in its action much more closely than it does unmodified insulin.
How do I remove glycation?
You’ll need to use something that’s super high in vitamin C if you want to improve the texture and firmness of skin that has been weakened by glycation. Vitamin C protects skin cells against glycation by boosting collagen synthesis and improving the actual structure of the skin.
Are anhydrides hydrophobic?
1.10. Anhydride groups (a) in backbone and (b) as side chain. In general terms, polyanhydrides have a hydrophobic backbone where anhydride bonds are subjected to hydrolysis because they are very water-labile; these polymers degrade with a surface erosion.
Is PLGA natural or synthetic?
13.7. 8 Polylactic Glycolic Acid (PLGA) Based Ocular Delivery Systems. PLGA is a biodegradable aliphatic polyester-based polymer that comprises a synthetic copolymer of lactic acid (α-hydroxy propanoic acid) and glycolic acid (hydroxy acetic acid).