Design and Development of Immunomodulatory Antigen Delivery Systems Based on Peptide/PEG-PLA Conjugate for Tuning Immunity.

Cancer vaccines are considered to be a promising tool for cancer immunotherapy. However, a well-designed cancer vaccine should combine a tumor-associated antigen (TAA) with the most effective immunomodulatory agents and/or delivery system to provoke intense immune responses against the TAA. In the present study, we introduced a new approach by conjugating the immunomodulatory molecule LD-indolicidin to the hydrophilic chain end of the polymeric emulsifier poly(ethylene glycol)-polylactide (PEG-PLA), allowing the molecule to be located close to the surface of the resulting emulsion. A peptide/polymer conjugate, named LD-indolicidin-PEG-PLA, was synthesized by conjugation of the amine end-group of LD-indolicidin to the N-hydroxysuccinimide-activated carboxyl end-group of PEG. As an adjuvant for cancer immunotherapeutic use, TAA vaccine candidate formulated with the LD-indolicidin-PEG-PLA-stabilized squalene-in-water emulsion could effectively help to elicit a T helper (Th)1-dominant antigen-specific immune response as well as antitumor ability, using ovalbumin (OVA) protein/EG7 cells as a TAA/tumor cell model. Taken together, these results open up a new approach to the development of immunomodulatory antigen delivery systems for vaccine adjuvants and cancer immunotherapy technologies.

Solubilization of water-insoluble drugs due to random amphiphilic and degradable poly(dimethylmalic acid) derivatives.

Amphotericin B (AmB) and clofazimine are potent drugs hindered by their low water solubilities and their toxicities. Carriers able to increase their apparent water solubilities are needed for these drugs and for other molecules with similar properties. Random amphiphilic copolymers derived from poly(dimethylmalic acid) were obtained using different hydrophobization ratios and side group sizes. Apparent water solubilities of pyrene, clofazimine, and AmB were increased up to 10 000, 20 000 and 1000 times, respectively, in aqueous solutions containing these polymers. The presence of sodium chloride in polymer solution increased pyrene solubility but decreased the solubilities of clofazimine and AmB, compared to the salt-free solutions. Synergy between hydrophobic and electrostatic interactions was observed for polar and cationic molecules. Degradation studies showed that the examined polymers were degradable, but none of them were totally degraded in 28 days. These polymers could be used as a new tool for drug solubilization.

Nanoaggregates of biodegradable amphiphilic random polycations for delivering water-insoluble drugs.

Cationic amphiphilic random copolyesters were obtained by copolymerization of 5-Z-amino-δ-valerolactone and ε-caprolactone. The amino content of the final copolymers was controlled by the polymerization feed ratio and was in the range 10 to 100%. Copolymers solubility and aggregation behavior was assessed by conductometric and zeta potential analyses. A critical aggregation concentration of ca. 0.05% (w/v) was found for all water-soluble copolymers that formed nanoaggregates. Two populations were found to be present in equilibrium with hydrodynamic diameters in the range of 30-50 and 100-250 nm. The capacity to use the amphiphilic and cationic character of the nanoaggregates to encapsulate highly hydrophobic compounds was further investigated. Finally, copolymers hemo- and cytocompatibility were evaluated by hemagglutination, hemolysis, and cells proliferation tests. The results showed that the proposed cationic amphiphilic random copolyesters are biocompatible.

Nanoaggregates of a random amphiphilic polyanion to carry water-insoluble clofazimine in neutral aqueous media.

Clofazimine, an antibiotic drug active against mycobacteria and used for the treatment of leprosy, is a very weak base insoluble in neutral aqueous media. It may cause rather severe secondary effects. Basically, these two shortcomings can be minimized by combination with a drug carrier. The potential of a polymeric carrier composed of nanosized aggregates formed by hydrophobized poly(methyl vinyl ether-alt-maleic acid) to solubilize clofazimine in neutral aqueous media and to administer it to mice was investigated. This amphiphilic polyanion was synthesized by partial esterification of commercial poly(methyl vinyl ether-alt-maleic anhydride) by dodecanol. An aggregate-forming analog bearing mannose residues aimed at targeting mannose receptors born by macrophages was also synthesized and characterized. In the presence of the aggregates, rather large amounts of clofazimine were compatibilized with neutral aqueous media. Comparison with a water-insoluble neutral dye, namely yellow OB, showed that the apparent solubilization of clofazimine was due to a synergistic combination of electrostatic and hydrophobic interactions and not only to the latter as in the case of yellow OB. Despite its favorable in vitro characteristics, clofazimine entrapped within the lipophilic pockets born by the amphiphilic aggregates exhibited no antibiotic activity after administration to mice infected with Mycobacterium bovis BCG.

Bioresorbable polyelectrolyte amphiphiles as nanosized carriers for lipophilic drug solubilization and delivery.

Starting from drug carriers and drug-delivery systems described in the literature, this article examines more specifically those that are relevant to the field of nanocarriers composed of a degradable hydrophilic polyelectrolyte backbone with pendent hydrophobes arranged to form comb-like co-polymers. Advantage is taken of the nanosized, lipophilic pocket-bearing multimolecule aggregates formed in aqueous media by such amphiphilic polyelectrolytes to accommodate water-insoluble drug molecules according to a phenomenon named macromolecular microencapsulation. Comments are also made on the criteria to be fulfilled by nanosized polymeric drug carriers. These carriers require a size or molar mass high enough to avoid renal excretion and thus be retained in the body for longer periods of time than the free drug. Since they nevertheless have to be eliminated from the body (bioresorption), they must be degraded at the end of use. In situ degradation is an important criterion that is taken into account by using special polyelectrolytes that belong to the class of the so-called "artificial biopolymers". Artificial biopolymers are made of pro-metabolite units than generate metabolite upon degradation, thus resulting in metabolisation of degradation end-products if intermediates are not excreted before. Aggregates of amphiphilic polyanions derived from malic acid, citric acid, L-lysine and L-serine are presented to support the concept of macromolecular microencapsulation. Comparison is made with non-polyelectrolytic systems with similar structures.

Synthesis, degradation, and antimicrobial properties of targeted macromolecular prodrugs of norfloxacin.

Long-term antibiotic treatment is required to cure tuberculosis. Targeted antibiotics should improve the efficacy of treatment by concentrating the drugs close to the bacteria. The aim of the present study was to synthesize targeted conjugates. For this purpose, we used mannose as a homing device to direct norfloxacin into macrophages. Dextran was used as the polymer bearing both mannose and norfloxacin. Using different peptide spacer arms to link norfloxacin to dextran, we demonstrated that norfloxacin acts as an antibiotic only when it is released in its native form. Also, targeting by using mannose as a homing device is required to achieve antimycobacterial activity in vivo. Thus, norfloxacin, which is inactive against mycobacteria in its native form in vivo, can be transformed into an active drug by targeting.