Halloysite clay nanotubes are natural abundant alumosilicate material which are being employed for loading and sustained release of anti-corrosives, flame retardants and antibacterial formulations. Given their nano scale dimensions (diameter 50 ± 5 nm; inner lumen 15 nm; length 1200 ± 300 nm), they are also being explored as a material for loading bio macromolecules such as proteins, DNA and drugs. Halloysite is a biocompatible material with low cell toxicity of 0.5 mg/mL. In order to make halloysite safer for cellular delivery of active agents, they can be coated with polyethylene glycol (PEG). In the current study, halloysite nanotubes were coated with the polymers poly (allylamine hydrochloride) (PAH) and poly (sodium 4-styrenesulfonate) (PSS) as an initial bilayer and a final bilayer of block-copolymers of poly-l-lysine [16 kDa]-block copolymer with PEG [5kDa] (PLB) using layer-by-layer (LBL) technique. Zeta potential measurements indicated a change in surface charge from -15 mV (native halloysite) to +38 mV (final cationic bilayer). Cytotoxicity studies using in vitro cell cultures were performed using native halloysite and PSS/PLB coated halloysite to determine the least toxic material as compared with pristine nanotubes. The same LbL-tube encapsulation was used to further extend the release of the anti-cancer drug camptothecin. Release studies of camptothecin from pristine halloysite and LBL-coated halloysite were compared indicating that the release was slower from the encapsulated tubes. A bioactivity test on brain tumor cancer cells using camptothecin by itself, halloysite and LBL-coated halloysite loaded with the drug demonstrated higher efficiency of the LbL nanotube formulation.

Controlled release of camptothecin from halloysite nanotubes coated with block-copolymers of polylysine with polyethylene glycol

251st National Meeting (2016)

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