Mark Pothecary studied biochemistry at the University of Bath before getting his PhD at the William Harvey Research Institute, part of the Queen Mary University. He joined Malvern in February 2008 at a technical specialist for DLS and GPC/SEC in the UK and is now the Product Manager for GPC/SEC products in the Americas.
Poly(D,L-lactide-co-glycolic acid), PLGA, is a copolymer of polylactic acid and polyglycolide. As a biodegradable and biocompatible polymer, it is has found use in a number of medical devices such as grafts and sutures as well as in drug delivery applications. Drug delivery profiles will be dependent on the molecular weight, composition and structure of the polymer. Gel-permeation chromatography (GPC) is the most widely used tool for the measurement of molecular weight and molecular weight distribution of natural and synthetic polymers. Static light scattering detectors measure the intensity of light scattered by the sample as it elutes from the column. Since the intensity of the scattered light is proportional to the sample’s molecular weight and concentration, they allow the direct measurement of the sample molecular weight independent of its elution volume. A viscosity detector can also be used as part of a GPC system to measure the parameter of intrinsic viscosity. In combination these data allow detailed structural information of a polymer to be generated in a single GPC measurement which can be compared with other samples in Mark-Houwink plots. In this paper, we analysed different samples of commercially available PLGA to compare their absolute molecular weight from light scattering to those quoted with the product using Malvern’s latest GPC/SEC system, OMNISEC. Structural differences between samples of different composition are clear. More detailed analysis of these parameters can be used to better control the end-properties of the PLGA and its release rate of drugs in delivery applications.
Alexandre Samoylov has received his PhD in Molecular Biology at the age of 27 years from the Institute of Molecular Biology (Kiev, Ukrane). He has completed postdoctoral studies at the DLO-Center for Plant Breeding and Reproduction Research (Netherlands) and at the Institute of Plant Genetics & Crop Plant Research (Germany). At present, he holds a Research Fellow IV position at the Scott-Ritchey Research Center Auburn University College of Veterinary Medicine (USA). He has published more than 40 papers in peer-reviewed journals. His current focus is on development of phage- and DNA-based vaccines for animals.
DNA vaccination is achieved by injecting an animal with genetically engineered DNA to stimulate antigen-specific immunological responses. One of the greatest advantages of DNA vaccines is that they are able to activate both arms of the immune system, humoral and cell-mediated. Potency of DNA vaccines can be increased drastically (hundreds of times) via advanced delivery methods. Even though muscle was the first and is the most traditional site for DNA injections, skin was shown to be an immunologically superior site for DNA immunization due to abundant presence of immune cells such as Langerhans and dendritic cells. This study reports the development of DNA-based contraceptive vaccines constructed to stimulate effective immune responses against pituitary cells expressing gonadotropin releasing hormone receptors (GnRHR). Two delivery routes for the constructed vaccines were tested in mice, 1) intramuscular injection into quadriceps muscle, and 2) intradermal injection of the ear pinna. Inoculation of the ear pinna, but not intramuscular injection, was shown to stimulate immune responses leading to suppression of testosterone (indirect indicator of the vaccine efficacy) and decreased expression of GnRHR mRNA that might be due to partial ablation of pituitary gonadotropes expressing GnRH receptors. The success of the intradermal delivery might be explained by the special structure of the pinna, which consists of two layers of epidermis and dermis (separated by ear cartilage) containing a high number of dendritic cells (most effective APCs) within a restricted area connected with major superficial cervical draining lymph nodes. Funded by Found Animals Foundation, Michelson Grant in Reproductive Biology D1213-F13.