Multiphoton and Harmonic Generation Imaging Methods Enable Direct Visualization of Drug Nanoparticle Carriers in Conjunction with Vasculature in Fibrotic Prostate Tumor Mouse Model

摘要

Prostate cancer (PCA) is the most common cancer and the third most common cause of cancer death in men.Targeted nanoparticles (NPs) that deliver effective doses of chemotherapeutic drugs specifically to PCA couldimprove chemotherapy efficacy without the toxicities. In the relevant mouse models, the direct visualization ofsuch drug nanoparticles along with the vasculature and fibrillar collagen matrix at submicron resolution arecritically important for the accurate measurements of the drug distribution in the tissue matrix. Multiphotonmicroscopy, which uses ultra-short IR laser pulses as the excitation source, produces multiphoton excitationfluorescence (MPEF) signals from exogenous or endogenous fluorescent proteins and induces specific secondharmonic generation (SHG) signals from non-centrosymmetric proteins such as fibrillar collagens. The objectivehere is to visualize and quantify the 3D distribution of an aptamer conjugated calcium phosphosilicate baseddrug nanoparticle carriers along with vasculature and tissue matrix in ex vivo thick mouse prostate tumor tissuewith submicron resolution. Human prostate tumor xenografts were established in athymic mice by injectingprostate cell line derived from human (PC-3 cells) and were grown for 4 weeks. Near-infrared imaging agentindocyanine green (ICG) loaded calcium phosphosilicate nanoparticles (CPSNPs) including targeted CPSNPsbioconjugated with DNA Aptamer, empty non-ICG containing CPSNPs (Ghost) and Dil (for blood vesselpainting) were injected into the tail vein. The spectral unmixing was performed to extract Dil signal from ICGsignal using measured emission spectra. The 3D reconstructions and subsequent quantitation showedaccumulation of ICG in blood capillaries versus tissue matrix. We here conclude that this multiphoton basedmultimodal imaging approach can provide spatially resolved 3D images with spectral specificities that aresensitive enough to identity and quantify the distributions of drug nanoparticle carriers in conjunction withvasculature and tissue matrix in prostate tumor with structural precision.