The neutrophil response to polystyrene microspheres bearing defined surface functional groups

Controlled release of dexamethasone from peptide nanofiber gels to modulate inflammatory response

New biomaterials that have the ability to locally suppress an immune response could have broad therapeutic use in the treatment of diseases characterized by acute or chronic inflammation or as a strategy to facilitate improved efficacy in cell or tissue transplantation. We report here on the preparation of a modular peptide amphiphile (PA) capable of releasing an anti-inflammatory drug, dexamethasone (Dex), by conjugation via a labile hydrazone linkage. This molecule self-assembled in water into long supramolecular nanofibers when mixed with a similar PA lacking the drug conjugate, and the addition of calcium salt to screen electrostatic repulsion between nanofibers promoted gel formation. These nanofiber gels demonstrated sustained release of soluble Dex for over one month in physiologic media. The Dex released from these gels maintained its anti-inflammatory activity when evaluated in vitro using a human inflammatory reporter cell line and furthermore preserved cardiomyocyte viability upon induced oxidative stress. The ability of this gel to mitigate the inflammatory response in cell transplantation strategies was evaluated using cell-surrogate polystyrene microparticles suspended in the nanofiber gel that were then subcutaneously injected into mice. Live animal luminescence imaging using the chemiluminescent reporter molecule luminol showed a significant reduction in inflammation at the site where particles were injected with Dex-PA compared to the site of injection for particles within a control PA in the same animal. Histological evidence suggested a marked reduction in the number of infiltrating inflammatory cells when particles were delivered within Dex-PA nanofiber gels, and very little inflammation was observed at either 3 days or 21 days post-implantation. The use of Dex-PA could facilitate localized anti-inflammatory activity as a component of biomaterials designed for various applications in regenerative medicine and could specifically be a useful module for PA-based therapies. More broadly, these studies define a versatile strategy for facile synthesis of self-assembling peptide-based materials with the ability to control drug release.

Circulation time and body distribution of 14C-labeled amino-modified polystyrene nanoparticles in mice

Commercially available amino-modified polystyrene particles of size range 100-1,000 nm were radioactively labeled with [14C]-formaldehyde. A study of the circulation time and body distribution of these particles was carried out in mice. The animals were sacrificed at 1-30 min after intravenous administration of the particles. The blood and organ (liver, spleen, lung) profiles of particles were determined by measuring their radioactivity by means of liquid scintillation counting. In general, larger particles were eliminated from blood faster than smaller particles. The blood elimination half-life ranged from 1.36 to 4.92 min. The particles were mainly taken up by the liver with larger particles being taken up faster than the smaller particles. At 30 min after injection, 60% of the administered 100 nm particles were present in the liver, whereas 85% of the 100 nm particles were found in the liver. Accumulation in the spleen was 1-3% of the total number administered in the entire size range. At 1 min after injection, less than 3% of the total dose administered was present in the lungs and this value decreased rapidly to less than 1% at 2 min. The only exception occurred for 100 nm, where 2.35% was present in the lungs at 2 min after injection.

Relationships between the structure and function of lipopolysaccharide chemotypes with regard to their effects on the human polymorphonuclear neutrophil

Polymorphonuclear neutrophils (PMN), harvested from healthy volunteers, were challenged with endotoxins from Salmonella minnesota smooth-strain and rough-strain mutants (Ra, Rb2, RcP-, Rd1P- and Re) as well as with lipid A in an effort to determine the relationship between lipopolysaccharide (LPS) structure and its ability to affect PMN chemotaxis (CT), random migration (RM) and luminol-dependent chemiluminescence (CL). In the presence of untreated autologous serum (UAS), as has been previously demonstrated for CL, CT in a modified Boyden chamber is stimulated but no significant differences among the chemotypes were observed. In the presence of heat inactivated autologous serum (IAS), significant variations among the LPS chemotypes occurred. Also noteworthy was the observation that, although the total number of cells migrating across the membrane was similar for both UAS and IAS, UAS promoted PMN migration beyond the membrane into the chamber, as opposed to IAS which caused the cells to remain adherent to the distal face of the membrane. In the absence of serum, RM was inhibited in a dose-dependent fashion by LPS from lipid A and the rough-strain mutants, with the degree of inhibition being progressively greater with increasing molecular complexity of the chemotype LPS. The smooth-strain LPS exerted an intermediate effect. In the case of CL, lipid A was the most potent stimulus, with the response decreasing as molecular complexity increased up to RcP-; the remaining core mutant LPS provided slightly greater responses. The LPS from the smooth-strain promoted a response similar to the response to Ra LPS. Based on these data, it is concluded that there are qualitative as well as quantitative effects of the carbohydrate moieties of LPS. These data also suggest that while LPS may provoke active migration in the circulation during endotoxemia, infection localized in tissue might bring about an inhibition of PMN migration while allowing the PMN to mount an oxidative response.