Natural degradable hydrogels

Enzyme-Degradable Hydrogel. Because lysozyme is a well characterized enzyme, our first choice was a lysozyme-degradable hydrogel (11, 12). The natural substrate for lysozyme is chitin (13). but because chitin is a rigid, hydrophobic material, it is clearly not suitable for this work. The other natural substrates for lysozyme are certain bacterial cell-wall peptidoglycans (13. 

The commonly used polymer for preparing degradable hydrogels are PVA, PEG, PVP, puronic polyol, and some natural polymers including cellulose and alginate (80). 

Semisolid Dosage Forms The nature of the base (vehicle) used for the fabrication of semisolid dosage forms affects their hydrolytic stability. Increased degradation of benzylpenicillin sodium in hydrogels of various natural and semisynthetic polymers has been reported [14]. Also at pH 6 in Carbopol hydrogels, the percentage of undecomposed pilocarpine at equilibrium is a function of the apparent viscosity of the medium [15]. 

Hydrogels that are based on natural products are more acceptable from the standpoint of toxicity-related issues and are therefore preferable to azo-based polymers. However, chemical derivatization, if performed without proper understanding, can lead to modifications of the hydrogels to products that will not degrade readily in the colon because it is possible that the new structures will not be recognized by the colonic bacterial enzymes for degradation. Also, bulk degradation is preferred to surface erosion because it... 

Because water is ubiquitous both in the sensing environment and inside many sensors (especially electrochemical sensors), the hydrophobic or hydrophilic nature of a polymer used in a sensor is often crucial. For example, a polymer that is to be used as a hydrogel is by definition hydrophilic. On the other hand, gas-permeable membranes are often made of hydrophobic polymers to prevent passage of water through the membrane. These conventions are not always the case, however. An electrolyte for a sensor operating with non-aqueous electrochemistry may be less hydrophilic. Similarly, an in situ sensor to analyse polar degradation products in motor oil may use a hydrophilic membrane to allow passage of the analyte into the aqueous electrolyte from the non-polar hydrocarbon sample [14]. 

In addition, the degradation properties of hydrogels were adjusted by incorporation of degradable linkers. By using enzyme-sensitive peptide sequences, cell-responsive biomaterials that mimic the proteolytic recognition of natural ECMs... 

Focus has changed with time from nonabsorbable to absorbable polymers. Absorbable polymers typically take the form of fibrous meshes, porous scaffolds, or hydrogels. If the polymer can degrade at a controlled rate, the body s own cells can infiltrate the matrix and replace the polymer space with natural tissue. The use of an absorbable polymer can have many advantages, such as the following ... 

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