Acidic pH-targeted chitosan capped mesoporous silica coated gold nanorods facilitate detection of pancreatic tumors via multispectral optoacoustic tomography.

We present a cancer nanomedicine based on acidic pH targeted gold nanorods designed for multispectral optoacoustic tomography (MSOT). We have designed gold nanorods coated with mesoporous silica and subsequently capped with chitosan (CMGs). We have conjugated pH-sensitive variant 7 pHLIP peptide to the CMGs (V7-CMG) to provide targeting specificity to the acidic tumor microenvironment. In vitro, treatment of S2VP10 and MiaPaca2 cells with V7-CMG containing gemcitabine resulted in significantly greater cytotoxicity with 97% and 96.5% cell death, respectively than gemcitabine alone 60% and 76% death at pH 6.5 (S2VP10 pH 6.5 p=0.009; MiaPaca2 pH 6.5 p=0.0197). In vivo, the V7-CMGs provided the contrast and targeting specificity necessary for MSOT of retroperitoneal orthotopic pancreatic tumors. In the in vivo S2VP10 model, the V7-CMG particle preferentially accumulated within the tumor at 17.1 MSOT a.u. signal compared with 0.7 MSOT a.u. in untargeted CMG control in tumor (P = 0.0002). Similarly, V7-CMG signal was 9.34 MSOT a.u. in the S2013 model compared with untargeted CMG signal at 0.15 MSOT a.u. (P = 0.0004). The pH-sensitivity of the targeting pHLIP peptide and chitosan coating makes the particles suitable for simultaneous in vivo tumor imaging and drug delivery.