(141g) Programmable Biohybrid Nanocarriers for the Sustained Release of Cancer Therapeutics

Cancer is the second leading cause of death worldwide. It is estimated that 1.9 million new cases and 608,570 deaths due to cancer will emerge in 2021 alone. Due to the excessive costs of cancer diagnosis and treatment the projected costs will reach $246 billion by 2030 in the US. As a result, the quest for a cost-effective cancer therapy with broad applications across cancer and patient types has garnered significant interest. Two of the most impactful innovations in the fight against cancer in the past few decades have been immune therapy and polymeric nanocarriers. Using these strategies, effective treatments have been developed that can trigger the patient’s immune system to attack cancer cells or accumulate therapeutics in cancerous tissue through the enhanced permeability and retention effect (EPR). However, due to drug resistance mechanisms unique to cancers, a number of recalcitrant cancers still have poor prognosis and metastasis lowers survivability for all cancer types. Therefore, an elegant nanocarrier - with high drug payload, delayed or triggered release, and tailorable targeting components – has the chance to revolutionize modern cancer treatment. The availability of commercially synthesized oligonucleotides has flooded the field with novel nucleic acid nanostructures, therapeutics, and biosensing elements (including the excellent molecular targeting capabilities of aptamers). The invention of spherical nucleic acid particles created a new class of nanocarrier whose potential is still being realized. Evidence has shown that specifically oriented oligonucleotides on spherical nanoparticle supports are highly stable, resistant to opsonization, produce a lesser immune response than free nucleic acids, and are internalized into cells without an additional transfection reagent. Additionally, work from our lab has pioneered sustained release from nucleic acid polymers through affinity modulation, only possible for small molecules through careful selection of the nucleic acid sequence (i.e., aptamer recognition). Thus, by tailoring the architecture of our novel biohybrid nanocarrier, we are able to program the particle according to the design principles for creating effective therapeutic nanocarriers: bioavailability, payload retention, and targeted delivery. We coat a 15 nm gold nanoparticle (AuNP) with short, duplexed oligonucleotides (dsAGC) chosen for their high affinity toward the chemotherapeutic daunomycin. A single stranded oligonucleotide (ssANC) is then conjugated alongside the dense duplex layer by way of a charge-neutral PEG spacer and can be used to hybridize additional oligonucleotides. The completed platforms are less than 100 nm in diameter and are resistant to serum protein adhesion compared to similar particles made with only single-stranded DNA. Each dsAGC oligonucleotide is able to bind 3-4 molecules of daunomycin and they are conjugated at a density of greater than 100 oligonucleotide per AuNP. The high affinity of daunomycin to the AGC motif results in a sustained release of daunomycin over more than 48 hours. Additionally, we show that dexamethasone can adhere directly to the gold surface and that the release rate can be controlled by increasing the density of DNA on the AuNP. In conclusion, we have developed a novel, biohybrid nanoparticle that can load and release at least two distinct chemotherapeutics. The high DNA density and structure of the resultant particles imbue a resistance to protein adhesion, likely due to steric hindrances. The small size of the particles will allow them to exploit the EPR effect of solid tumors. Additionally, the ssANC oligonucleotide can hybridize with complementary sequences making them programmable with targeting aptamers, peptides, or monoclonal antibodies, providing active targeting capabilities. As personalized medicine techniques provide improvements to active cancer targeting, we expect that our design will provide an essential platform for the delivery of chemotherapeutics to a broad range of cancer types.