**7. Acknowledgement**

270 Biomedical Science, Engineering and Technology

In 2004, Sculptra™ [poly(*L*-lactic acid)] was approved by the FDA as the first injectable facial "volumizer" in the treatment of lipoatrophy due to its significant therapeutic effectiveness (Burgess & Quiroga, 2005). The lipodystrophy syndrome is associated with the usage of highly active antiretroviral therapy (HAART) containing protease inhibitors or nucleoside reverse transcriptase inhibitors for HIV patients. The action mechanism of Sculptra™ is via stimulation of the fibroblastic activity with generation of collagen and other connective tissue fibers. In addition, it acts as dermal matrix adding support by thickening the dermis (Vleggaar & Bauer, 2004). Moreover, PLA can help improve the appearance of scars due to acne, surgery, trauma, or suture (Lowe & Beer, 2005, as cited in Beer & Rendon,

Due to the multiple desirable characteristics of PLA including renewability, biocompatibility, transparency, and thermoplasticity, it is being used or is a potential candidate for many consumer and biomedical applications (Jamshidian et al., 2010). Ever increasing environmental concerns associated with conventional polymers derived from petrochemicals lead to constantly expanding applications for PLA since its discovery in 1932

In previous years, the most negative point of PLA was its higher price as compared with petrochemical-based polymers. Today, by optimizing the LA and PLA production processes, and with increasing PLA demand, a reduction in its price can be achieved. The price of PLA is currently much lower than in previous years. Meanwhile, PLA is mainly synthesized in the industry by ROP employing tin(II) bis(2-ethylhexanoate) (SnOct2) as a catalyst, which has been approved as a food additive by the FDA, but the potential toxicity associated with most tin compounds cannot be ignored for biomedical applications. Scientists all over the world are now exploring novel, well-defined catalysts with good biocompatibility, high catalytic activity, low toxicity, and excellent stereoselectivity. This should remain an everlasting interest area. Finally, the possibility of obtaining 100% biosourced opens the way for PLA to become more independent from petrochemical-based

However, the major disadvantages of PLA such as its poor ductility, slow degradation rate, and poor hydrophilicity somewhat limit its applications. The modification of PLA bulk and surface properties has thus become crucial to increase its applicability. Many of the bulk and surface modification strategies discussed above have been designed to tune the PLA surface properties according to the demands of biomedical applications. Unfortunately, all these established methods for surface modification are somewhat deficient and while they provide control over the wettability, degradation rate, and functionality, it is still compulsory to minimize their negative impact on PLA bulk properties. Thus a combined modification strategy (e.g. irradiation followed by grafting) or a better balance of PLA surface and bulk properties should be sought. Ideally, with respect to a better balance of properties and shorter modification times, one-step approaches need to be developed because it is time-consuming to carry out surface and bulk modifications separately, and the solvents and reagents involved in multiple modification steps tend to affect PLA properties

All these modification strategies aim at tailoring the properties of PLA-based materials for certain applications. Fortunately, more and more encouraging results have been reported,

2006).

**6. Conclusions** 

by Carothers at DuPont.

significantly.

polymers, free of environmental and health concerns.

It was supported by the Natural Science of Hubei Province for Distinguished Young Scholars (No. 2008CDB279) and the Key Technologies R & D Program of Hubei Province (20091933), the Fundamental Research Funds for the Central Universities, Huazhong University of Science and Technology (2010JC016) and the National High Technology Research and Development Program ("863" Program) of China (No. 2008AA10Z339). The authors are also grateful to Dr. Wen-bin Zhang from the University of Akron for his valuable suggestions during the preparation of this manuscript.

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