ABSTRACT
BACKGROUND:Subdermal contraceptive implants as a novel contraceptive method have been extensively used worldwide.OBJECTIVE:To review the research progress in the non-biodegradable and biodegradable long-term subdermal contraceptive implants and to explore their advantages and disadvantages.METHODS:A computer-based search of CNKI,Wanfang,and PubMed (1967-2015) was performed by the first author for relevant articles,using the key words of contraceptive implants,non-biodegradable,biodegradable in Chinese and English,respectively.Initially 240 articles were retrieved,and finally 70 articles were included in result analysis.RESULTS AND CONCLUSION:Long-term subdermal contraceptive implants that pass through the local capillaries into the blood circulation system can avoid the gastrointestinal absorption,improve the bioavailability of drugs,and reduce adverse drug reactions.According to the performance,there are two kinds of drug carriers,non-biodegradable and biodegradable.Although non-biodegradable implants have been widely used and the contraceptive effect is excellent,the implants must be removed surgically because they cannot be absorbed or metabolized in the body.Significant efforts have been devoted to developing biodegradable implants because they can degrade at the end of use.However,the utility of some biodegradable polymers as drug carriers in implantable applications has been hampered by their shortcomings,and further study on alternative materials is urgently required.
ABSTRACT
BACKGROUND:Currently, biodegradable polymer materials such as poly(morpholine-2, 5-dione) and its derivatives have been widely used in biomedical field to fabricate nerve catheters, tissue engineering and drug control release carriers. Therefore, many research has focused on the synthesis of poly(morpholine-2 5-dione) and its derivatives. OBJECTIVE:To review the synthesis methods of monomeric and polymeric morpholine-2, 5-dione and its derivatives, and to explore its advantages and shortcomings. METHODS:A computer-based search of databases of Wanfang, CNKI, SCI and PubMed was performed for relevant articles published from 1982 to 2015. And the keywords were“morpholine-2, 5-dion, biodegradable”in Chinese and English, respectively. RESULTS AND CONCLUSION:So far, acylation reactions ofα-amino acids andα-halogen halide, the intramolecular esterifications and intramolecular condensation reactions are the key methods for the synthesis of morpholine-2, 5-dione and its derivatives. A modified approach is needed to overcome the existed disadvantages. Ring-opening polymerization of morpholine-2, 5-dione is a preferred method of synthetic polyester-amide, but low molecular weight and conversion of polymers are produced. Polymerization catalyzed via metal compounds and enzymes are the best strategy for the synthesis of poly(morpholine-2, 5-dione). Furthermore, as a valuable biodegradable polymer material, poly(morpholine-2, 5-dione) has been extensively applied in the medical field.