Multifunctional Nanoemulsions for Systemic Delivery of Analgesic Peptides to the CNS

The blood brain barrier (BBB) prevents majority of potential drugs from reaching their central nervous system (CNS) targets. This has been a major obstacle to several therapies that are potentially useful in combating diseases that affect the CNS. Peptide and protein therapeutics possess unique physicochemical and biological properties; however, their delivery across the BBB is limited: while techniques like electroporation, chemical transfection or miro-injection can be applied to aid their delivery to target areas, this often leads to cell damage, and besides, the amount of protein or peptide delivered to the brain is not easily controlled. There is an urgent medical need for delivery of biomolecules like opioid peptide analgesics across the BBB, for effective therapy of pain. The objective of this doctoral thesis project was to develop a safe and effective nanoemulsion-based delivery system that contains omega-3 rich polyunsaturated fatty acid (PUFA), plus an efflux modulator (curcumin), for effective delivery of encapsulated peptide across the BBB. This non-invasive, multi-modal strategy can overcome physical (i.e., tight junctions) as well as biological (i.e., efflux transport) barriers, and can potentially be applied in a clinical setting.;Oil-in-water (O/W) nanoemulsion formulations comprising of fish oil and the peptide (or curcumin or fluorescent label) and water phase (containing egg phosphatidylcholine and polysorbate-80), were prepared using ultrasonication. The particle size and TEM analysis confirmed their nano size distribution. Slight chemical modification of the analgesic peptide significantly improved its encapsulation in the oil phase of nanoemulsion, retaining the analgesic efficacy. Multiple cell culture models were screened to mimic the structural and/or functional aspects of the BBB. CaCO-2 cell monolayers demonstrated an effective permeability and intracellular uptake of nanoemulsion formulation. Curcumin showed a significant effect in downregulating various efflux transporters expressed on CaCO-2 cells and improving the permeability of solution formulation. This was supported by the pharmacokinetic and brain distribution data in vivo, with appropriate dosing regimen using curcumin nanoemulsion and peptide solution. In vivo acute pain model was developed and the analgesic potential of modified peptide in solution and nanoemulsion was proven. Whole brain imaging utilizing the functional MRI (fMRI) in an acute capsaicin-induced pain model, demonstrated the efficacy of analgesic peptide nanoemulsion in awake rats.;The PUFA-based nanoemulsion formulation efficiently delivers analgesic peptide to the brain. Thus, the novel multifunctional nanoemulsion offers an alternate, safe and effective drug delivery system for peptides to the CNS.