Increased covalent conjugation of a model antigen to poly(lactic acid)- g -maleic anhydride nanoparticles compared to ba
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ORIGINAL CONTRIBUTION
Increased covalent conjugation of a model antigen to poly(lactic acid)-g-maleic anhydride nanoparticles compared to bare poly(lactic acid) nanoparticles Víctor H. Orozco & Juliana Palacio & Jelver Sierra & Betty L. López
Received: 21 January 2013 / Revised: 25 June 2013 / Accepted: 27 June 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract Maleic anhydride (MA) grafted poly(lactic acid) (PLA) (PLA-g-MA) was synthesized from PLA. Proton nuclear magnetic resonance confirmed the grafting of the MA. PLA-g-MA and PLA were used to prepare polymeric nanoparticles. Particle size distributions were measured by dynamic light scattering, and colloidal stability was determined by (zeta) ζ-potential. The ζ-potential becomes more negative for PLA-g-MA than PLA nanoparticle dispersions, due to the presence of deprotonated carboxylic acid groups on the backbone of the PLA and confirms the MA grafting results. Maleic anhydride grafted on PLA backbone improves the covalent conjugation with ovalbumin (OVA) compared to OVA physically adsorbed on the particles. The chemical conjugation was carried out via amide linkages between the carboxylic groups of the nanoparticles, activated with 1ethyl-3-(3-dimethylaminopropyl)carbodiimide, and the amino groups of the protein. The amount of protein conjugated was measured by using the bicinchoninic acid method and is threefold higher compared to the adsorbed OVA. Moreover, the PLA-g-MA nanoparticles increased the amount of conjugated OVA by 36 wt% compared to PLA nanoparticles. OVA adsorption and OVA conjugation provided colloidal dispersions with excellent stability. Keywords PLA nanoparticles . Maleic anhydride . Grafting . H NMR . Ovalbumin . Adsorption . Chemical conjugation . (Zeta) ζ-potential
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V. H. Orozco (*) : J. Palacio : B. L. López Ciencia de los Materiales CIENMATE, Instituto de Química, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín, Colombia e-mail: [email protected] J. Sierra Grupo de Inmunomodulación GIM, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín, Colombia
Introduction Cancer and many infectious diseases remain a significant public health problem worldwide. Chemotherapy-based interventions for these diseases are often problematic due to their welldocumented toxicity in humans [1, 2]. Although effective vaccines for some bacterial and viral diseases are available, the development of effective vaccines for intracellular pathogens remains elusive [3–6]. Vaccines for both cancer and intracellular infections require the sustained induction of the cellular arm of the immune system, which, in contrast to the antibody-mediated response, has proven to be difficult to stimulate within acceptable margins of safety. Recent advances in immunobiology and nanotechnology are permitting the development of novel cellular adjuvants and particulate delivery systems which are expected to facilitate the development of new vaccines for the most important human diseases [7–9]. Biodegradab
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