ABSTRACT
BACKGROUND: Existing flaws have been found in the production process of poly(lactic-co-glycolic acid) (PLGA) copolymer microspheres, which lead to residual solvent, low drug loading rate and low encapsulation efficiency of sustained-release microspheres.OBJECTIVE: To review different methods for preparing PLGA microspheres from the following aspects: basic principles, advantages/disadvantages, indications and future development. METHODS: We retrieved CNKI, PubMed and Google scholar to access the articles related to the technique process of preparing PLGA microspheres published from January 2012 to April 2017, including experiment and application research on the principles and advantages/disadvantages of the various processes. RESULTS AND CONCLUSION: To date, the main methods to prepare PLGA microspheres include single/re-emulsion solvent evaporation method, spray drying method, hydrogel template method, microfluid, coaxial electrostatic spraying, phase separation method, and supercritical fluid extraction. However, no valid evidences suggest that there is a technique that completely solves all potential problems, such as drug encapsulation and release, residual solvent and appropriate shape and size. Combination and modification of the production processes is expected to develop novel PLGA microspheres with ideal encapsulation efficiency and stable drug release.
ABSTRACT
<p><b>OBJECTIVES</b>To investigate the mechanical properties of bilateral atlantoaxial trans-articular screws and atlas laminar hooks instrumentation with finite element method.</p><p><b>METHODS</b>There was a volunteer with age of 28 years old, body height 172 cm, body weight of 60 kg and without cervical deformity by X rays. The ligamentous, nonlinear, three-dimensional finite element models of normal upper cervical spine (C0-3) was developed and validated. The destabilized model with bilateral atlantoaxial trans-articular screws and atlas laminar hooks was evaluated for quasistatic loading.</p><p><b>RESULTS</b>The finite element model of upper cervical spine consists of 229,047 nodes and 152,475 elements, and correlated well with experimental data for all load cases and could be used for experiment. The finite model with bilateral atlantoaxial trans-articular screws and atlas-laminar hooks predicted that the maximum Von Mises Stress was in the region in which screws penetrated the atlantoaxial articular facet. The novel instrumentation resulted in sufficient stability.</p><p><b>CONCLUSION</b>The bilateral atlantoaxial trans-articular screws and atlas laminar hooks instrumentation is useful and effective for atlantoaxial arthrodesis.</p>