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The interactions of programmed death protein-1 (PD-1) on T cells with its ligand, PD-L1, strongly contributes to an immunosuppressive microenvironment. Blockades of PD-L1 have shown long-term survival in patients. However, <30% of patients respond to PD-L1 blockade, in part due to inaccurate identification of PD-L1 expression. An unmet clinical need exists for noninvasive detection techniques. Surface-enhanced Raman spectroscopy (SERS) imaging mediated by gold nanostructures has gained interest as a pre-clinical noninvasive diagnostic tool due to the high spatial resolution, portability, low cost, and rapid analysis. In this work, we demonstrate the use of gold nanostars conjugated with Raman tags for multiplexed SERS and simultaneous diagnosis of PD-L1 and epidermal growth factor receptor (EGFR) in vivo. Nanostars conjugated with anti-PDL1 antibodies/DTNB Raman molecule, and nanostars conjugated with anti-EGFR antibodies/pMBA Raman molecules were concurrently introduced to mice. Longitudinal Raman analysis demonstrated maximum accumulation of nanostars occurred 6h post IV delivery when strong increases in SERS signals for both Raman tags were observed. Raman signals decreased by 30% when both targeted receptors were pre-blocked with antibody (IP), indicating both the sensitivity and specificity of our platform in distinguishing tumors with varied expression of PD-L1 and EGFR. Furthermore, ex-vivo Raman maps provided assessment of biomarker status with cellular-resolution, and nanostars distribution in tumors. Finally, gold contents in organs were quantified with inductively coupled plasma mass spectrometry to evaluate their pharmacokinetics and biodistribution. This work shows gold nanostars-mediated SERS imaging provides a quantitative measure of PD-L1 to allow predictive and personalized immunotherapies with minimal toxicities.
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