Absorbable microparticulate cation exchanger for immunotherapeutic delivery

• Published in: Journal of biomedical materials research 2004-05, Vol.69B (2), p.173-182
• Main Authors: Shalaby, Waleed S. W., Yeh, Heidi, Woo, Edward, Corbett, Joel T., Gray, Heidi, June, Carl H., Shalaby, Shalaby W.
• Format: Article
• Language: English
• Subjects: absorbable polymers; Absorption; Animals; cation exchanger; CD28 Antigens - metabolism; CD3 Complex - metabolism; Cell Division; Cytokines - metabolism; Dendritic Cells - cytology; Dendritic Cells - metabolism; Drug Delivery Systems; Granulocyte-Macrophage Colony-Stimulating Factor - metabolism; Humans; immunotherapy; Immunotherapy - methods; Ion Pumps - chemistry; Ion Pumps - metabolism; Ion Pumps - therapeutic use; Lymphocyte Activation; Mice; Mice, Inbred BALB C; microparticulate; Neoplasm Transplantation; Neoplasms - immunology; Neoplasms - pathology; Neoplasms - prevention & control; Neoplasms - therapy; Particle Size; Polyglycolic Acid - chemistry; Polyglycolic Acid - metabolism; protein adsorption; Surface Properties; T-Lymphocytes - cytology; T-Lymphocytes - metabolism
• ISSN: 1552-4973; 0021-9304; 1552-4981
• DOI: 10.1002/jbm.b.20040

An absorbable microparticulate cation exchanger was synthesized as a versatile carrier for biologically active proteins. In this work, acid‐terminated polyglycolide (or polyglycolic acid) microparticulates (PG‐MP) were surface modified for either sustained release of cytokines or as a platform for immunomodulation. The intended goal was to achieve in situ recruitment/maturation of dendritic cells and activation of T cells for tumor immunotherapy. PG‐MP were prepared with a volume weighted mean diameter of 7.02 μ (range: 2.09–14.58 μ). Accessible carboxylic acid groups were determined to be 0.3 mmol/g with a corresponding zeta potential of −21.87 mV in phosphate‐buffered saline. Under low magnification, scanning electron microscopy (SEM) revealed a highly textured surface due to processing from repetitive jet milling. However, a moderately porous architecture was noted at higher magnification. Electron spectroscopy for chemical analysis was used to characterize the PG‐MP surface before and after adsorption of human granulocyte‐macrophage colony stimulating factor (GM‐CSF). Adsorption of GM‐CSF on PG‐MP (PG‐GMCSF) resulted in a modest increase in the surface atomic concentration of nitrogen (0.97%). Pretreating the surface with poly‐L‐lysine (PG/Lys‐GMCSF) prior to adding GM‐CSF produced a nearly threefold increase in the surface nitrogen concentration (4.20% compared to 1.47%). This manipulation not only increased loading content, but also prolonged the release of GM‐CSF released from 6 days to 26 days. ESCA on the post‐release PG‐MP samples (PG‐GMCSF and PG/Lys‐GMCSF) revealed a similar residual surface nitrogen concentration (2.26% vs. 2.35%). The observation was consistent with irreversibly adsorbed GM‐CSF. It is postulated that irreversibly bound GM‐CSF is released over time as a function of microparticulate degradation. Biological activity of released GM‐CSF was confirmed by the proliferation of a GM‐CSF‐dependent cell line (TF‐1) in the presence of microparticulates. PG‐MP mediated activation of T cells was achieved through irreversible adsorption of either antimouse cd3 plus antimouse cd28 monoclonal antibodies (α‐cd3/cd28‐MP) or antihuman CD3 plus antihuman CD28 monoclonal antibodies (α‐CD3/CD28‐MP) on PG‐MP. Irreversibly adsorbed antibodies were capable of activating both resting mouse and human T cells. Intracellular flow cytometry on mouse T cells revealed that nearly 50% of the activated cells produced interferon‐gamma (IFN‐γ). This was consiste