Tissue engineering has developed dramatically over the last 10 years which aims to restore, maintain, or improve tissue functions that are defective or have been lost by different pathological conditions, either by developing biological substitutes or by reconstructing tissues. Scaffolds plays a unique role in tissue regeneration and repair and have been used for tissue engineering such as bone, cartilage, ligament, skin, vascular tissues, neural tissues, and skeletal muscle and as vehicle for the controlled delivery of drugs, proteins, and DNA. In scaffold design and application, polymers have been widely used as biomaterials for the fabrication of medical device and tissue-engineering ...view middle of the document...
The glass transition temperature ranges between 35-40 degree℃ and its melting temperature is above 200 degree℃. PGA is a biodegradable polymer which is comparatively suitable for different medical applications such as resorbable sutures. With excellent degradability, it is commonly and effectively applied in scaffolding material for tissue regeneration as it provides good mechanical properties for cell viability.
Moreover, PGA has good skin restoring ability (Pathiraja A and Raju, 2003,) which does not require suture after surgery and then enhances the biological tissue regeneration. One of the main reasons why PGA is one of the most popular polymers is that the degradation product is a neutral substance. After degraded into glycolic acid, PGA is broken down into glycine and excreted in urine or carbon dioxide. There are two steps of reaction of the PGA degradation which is corrosive. Firstly, water enters into the amorphous matrix and the ester group of the hydrolytic chain. Secondly, the degradation process mostly happens in crystalline areas of the polymer, which most of the amorphous region is eroded and it then becomes predominant. After these two reactions, PGA will be hydrolyzed by enzyme and the product glycolic acid which may enter into tricarboxylic acid cycle and subsequently will be removed via respiratory system (Lakshmi S and Cato T, 2007,).
Importantly, there are some drawbacks in the application of PGA. Firstly, PGA has a high rate of degradation, as research data indicates that 50 percent of its strength may lose in two weeks and 100 percent in four weeks. Secondly, a high concentration of glycolic acid is likely to be absorbed in human body which may possibly lead to tissue damage due to accumulation of acid(Pathiraja A and Raju, 2003,).
2.2 Polylactic Acid.
Poly-lactic acid is a semi crystalline compound and chiral compound which contains three isomeric forms which are D (-), L (+) and racemic (D, L) polymer. Chiral compound contains an asymmetric center and has a non-superposable mirror image. Poly-L-lactic acid [PLLA] is about 37% crystallinity, the glass transition temperature is between 60 to 65 degree℃ and the melting point is between 175 to 178 degrees℃
ompared with PGA, the degradation time of PLLA is much slower as it takes about two to five years for full resorption in human body. The structure of PGA and PLLA is similar. However, PLLA is more hydrophobic and cannot be broken down by hydrolysis easily. The attractiveness of PLLA as a biodegradable polymer in medical application is a high strength fibers (Sabir and Xu et al., 2009,). High tensile strength (approximately 4.8GPa) and high modulus are essential for biomaterial which is more effective in load bearing. For example, applications include orthopedic fixation, scaffolding material for ligament replacement and augmentation device to replace mom-degradable fibers (Lakshmi S and Cato T, 2007,).
With these properties, PLLA fiber based polymer has been...