More than 98% of existing molecules cannot access the brain tissue because ofthe blood brain barrier (BBB). As a result, drugs that could be useful for central nervous system diseases cannot reach their targets efficiently and fail to exhibit acceptable therapeutic effect. The goal of the proposed research is to develop a highly selective and efficient system for drug delivery into the brain and to apply it to metal ion chelators that can solubilize AB aggregates and inhibit AB plaque formation associated with Alzheimer's disease. We hypothesize that by incorporating two targeting moieties into a pH and redox potential dual responsive nanogel, metal ion chelators, D-penicillamine (PA) and clioquinol (CQ) can be selectively targeted to the brain tissue and attenuate AB aggregation. Aim 1 is to develop a pH and redox potential dual responsive nanogel and explore the relationship between polymer structure and nanogel properties. In aim 2, we will load chelators or fluorescent dyes into dual targeted dual responsive nanogel (DTDR) with two braintargeting moieties (transferrin and glutathione) and measure DTDR efficacy and BBB penetration in vitro using a Transwell model. The neuroprotective effect of chelator-loaded DTDR will be compared with free drug counterparts and optimized by adjusting the densities of transferrin, glutathione, and polyethylene glycol. Aim 3 will assess the efficacy and BBB penetration of fluorescent dye or chelator-loaded brain-targeting DTDR in vivo. The composition of brain-targeted fluorescent DTDR will be optimized with IVIS imaging to achieve high selectivity for brain tissue in mice. The therapeutic efficacy of the brain-targeted PA or CQ-loaded DTDR will be quantified by measuring extracellular brain AB using in vivo microdialysis (IVM) in Tg2576 mice and compared with their free drug counterparts. Correlations between PA and CQ concentrations obtained from IVM, Zn and Cu residual in the brain tissue, amyloid plaque deposition from immunohistochemistry, and the residual AB in the brain tissue will be analyzed. Pharmacokinetic properties and systemic toxicity ofthe DTDR nanogel will also be evaluated. The success of this study should drastically increase the spectrum of drugs that can be developed for central nervous system diseases.

The impact of developing a brain targeted delivery system is extensive. Due to the versatility of proposed delivery system, the application of proposed dual targeted dual responsive nanogel is not limited to Alzheimer's disease. This unique platform can also be applied for the study and treatment of other diseases such as glioblastoma, Parkinson disease, Wilson's disease, and multiple sclerosis.