pH Triggered Sustained Drug Delivery from a Polymer Micelle having the b Thiopropionate Linkage.
The synthesis, micellar aggregation, and pH triggered intracellular drug delivery ability of an amphiphilic statistical copolymer (P2) are studied. Two methacrylate derivatives, one containing a hydrophilic pendant and the other containing a hydrophobic pendant chain, are copolymerized to produce P2. The hydrophobic pendant chain is linked to the polymer backbone by a b thiopropionate linkage, known to undergo slow hydrolysis at mild acidic pH. P2 forms a multimicellar cluster in water with a critical aggregation concentration of 0.02 mg mL( 1) and encapsulates a hydrophobic guest such as pyrene, Nile red, or the anti cancer drug doxorubicin (Dox) Sustained release of the entrapped Dox (80% after 100 h) is noticed at pH 5.2, while release is significantly slower (35% after 100 h) at pH 7.4. Acidic hydrolysis of the b thiopropionate linkage leading to the reduction of the hydrophobicity is established as the cause for micellar disassembly and triggered drug release. Cell culture studies with the human breast cancer cell line, MCF 7, reveal biocompatibility of P2 (below 150 mg mL( 1) It is further tested for intracellular delivery of Dox. MCF 7 cells remain healthy at pH 7.4 but become unhealthy at pH 5.2 when treated with a Dox loaded P2 micelles.
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