PROJECT SUMMARY/ABSTRACT The illicit use of synthetic opioids is on the rise, with Ohio being second in the nation per number of overdose deaths. In this regard, fentanyl is an easily accessible and potent analgesic that has been used in the clinic since the 1960s. With facile production and derivatization, this class of drugs has been a subject of abuse in which they are mixed with heroin to lead to overdose. Moreover, carfentanil was in the form of aerosol used in the terrorist attack in Moscow (2002) resulting in fatalities. With a variety of fentanyl derivatives produced in clandestine labs (mostly in China) and distributed for illicit use or available to terrorists, there is an immediate need for developing effective an easily accessible antidote with (a) no or minimal side effects, (b) easy implementation (injection), (c) rapid onset of action and (d) longer protection. Indeed, naloxone acts as an effective antagonist to reverse the effect of overdose but due to its rapid clearance it only provides a short-term protection. As the excess of lipophilic fentanyl distributes in tissues, its slow release into the bloodstream causes renarcotization. To address the issue as well as side effects, we hereby propose investigating the recognition of fentanyl and its derivatives using dual-cavity baskets assembled into nanoparticles (i.e., nano-antidotes). Dual- cavity baskets were developed in our labs to consist of two conjoined and cup-shaped frameworks sharing the same “floor” with each cup having three amino acids or PEG acids at its terminus. Importantly, polyvalent baskets trapped two molecules of anticancer anthracyclines in the positive allosteric fashion with ternary complexes assembling into circa 100 nm nanoparticles. These organic nanoparticles were nontoxic to HeLa cells and thermodynamically stable in PBS at physiological pH. With baskets being easily accessible and prone to rapid diversification, we hereby propose a strategy to functionalize them with biocompatible groups (amino acids, peptides and PEG acids) so that they, in the form of nanoparticles, trap fentanyl and its congeners in the positive allosteric manner. By forming stable nanoparticle/drug assemblies, the concentration of the drug in the bloodstream should drop causing a negative gradient in the concentration and therefore its removal from CNS and tissues. The circulation time of nanoparticles will, via chemical modifications, be tuned to be >24 h to permit the proposed pharmacokinetic mode of action. To identify basket hosts capable of strongly and allosterically complexing fentanyl, we will use tools of computational chemistry for selecting candidates for experimental study. From SARs, we will develop basic rules pertaining the effective recognition of fentanyls in PBS, serum and blood. Developing a fundamental understanding of the effective recognition of fentanyl and its derivatives with a modular abiotic host in competitive media will set the stage for studying cooper...