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Design, Synthesis, and Antimycobacterial Property of PEG–bis(INH) Conjugates

Poly(ethylene glycol) derivatives of isoniazid with varying molecular weight of poly(ethylene glycol) were designed as antimycobacterial agents. Poly(ethylene glycol)‐diacrylate of three different molecular weights (MW 258, 575, and 700) was conjugated with isoniazid by the Michael addition approach. The poly(ethylene glycol)–bis(isoniazid) conjugates thus obtained were completely characterized by FT‐IR, 1H and 13C NMR, and ESI‐MS spectroscopic techniques. Comparative MTT assay of the poly(ethylene glycol)–bis(isoniazid) conjugates showed much lower cytotoxicity than the neat isoniazid. MIC studies on Mycobaterium tuberculosis H37Rv showed potential antimycobacterial activity than the free isoniazid on a molar basis. The poly(ethylene glycol)–bis(isoniazid) conjugates were successfully radiolabeled with 99m‐Technetium with more than 97% efficiency and stability to assess their in vivo fate. The 99mTc labeled poly(ethylene glycol)–bis(isoniazid) conjugates showed higher blood retention time in New Zealand rabbits which increased with increasing molecular weight of poly(ethylene glycol). Biodistribution studies in infection‐induced murine models (BALB/c mice) showed significant retention of these conjugates at the site of infection for 72 h. The results of this study illustrate the potential utility of the PEGylated isoniazid conjugates as long circulating carriers for improved antitubercular drug therapy.