(683g) Star Shaped Silicon Microneedle Array for In-Vivo Melanoma Cancer Monitoring Via Cancer Exosome Isolation

This study reports a deep-reactive-ion-etched star shaped microneedle device (ExoNeedle chip) coated with a hybrid hydrogel that can directly capture cancer-associated extracellular vesicles (EVs) in interstitial fluid (ISF) in a minimally invasive manner, as opposed to conventional liquid biopsy methods involving sample extraction and EV isolation in-vitro or tissue biopsies for melanoma. Tumor derived EVs give insight into a tumor’s mutational burden and provide both prognostic and diagnostic value as a liquid biopsy tool. Melanoma is an aggressive cancer with a lack of promising markers for early detection, onset of metastasis, and monitoring of recurrence. The ExoNeedle chip is intended to pierce through the epidermis and parts of the dermis to isolate melanoma secreted EVs from the ISF to alleviate these unmet needs.

The microneedle arrays were created through the Deep Reactive Ion Etching (DRIE) process and a subsequent wet etching step to sharpen the needles. The DRIE parameters needed to be optimized to reduce undercut of the star shape on a 1mm thick silicon wafer to ensure proper sharpening. The needles are coated in a hybrid hydrogel consisting of polyvinyl alcohol and alginate conjugated with Annexin V (Av) protein to give it affinity for cancerous exosomes. The hydrogel is gelated with a calcium solution which can later be freed using ethylenediaminetetraacetic acid (EDTA) after binding with the cancerous EVs.

The ExoNeedle chip is validated using purified melanoma EVs both qualitatively and quantitatively. Nanoparticle tracking analysis is used to quantify capture and release efficiency along with a quantitative protein assay. Western blotting and scanning electron microscopy are used to qualitatively verify, as well as animal tissue models to investigate how well the ExoNeedle chip pierces skin.