Current trends in pyrrole and porphyrin-derived nanoscale materials for biomedical applications

This article is written to provide an up-to-date review of pyrrole-based biomedical materials. Porphyrins and other tetrapyrrolic molecules possess unique magnetic, optical and other photophysical properties that make them useful for bioimaging and therapy. This review touches briefly on some of the synthetic strategies to obtain porphyrin- and tetrapyrrole-based nanoparticles, as well as the variety of applications in which crosslinked, self-assembled, porphyrin-coated and other nanoparticles are utilized. We explore examples of these nanoparticles' applications in photothermal therapy, drug delivery, photodynamic therapy, stimuli response, fluorescence imaging, photoacoustic imaging, magnetic resonance imaging, computed tomography and positron emission tomography. We anticipate that this review will provide a comprehensive summary of pyrrole-derived nanoparticles and provide a guideline for their further development.

Targeting-triggered porphysome nanostructure disruption for activatable photodynamic therapy

Photodynamic therapy (PDT) and photothermal therapy (PTT) possess advantages over the conventional therapies with additional treatment selectivity achieved with local laser irradiation. Comparing to PTT that ablates target tissue via thermal necrosis, PDT induces target cell death via singlet oxygen without damaging the underling connective tissue, thus preserving its biological function. Activatable photosensitizers provide an additional level of treatment selectivity via the disease-associated activation mechanism. In this study, folate-conjugated porphysomes are introduced as targeting-triggered activatable nano-sized beacons for PDT. Porphysomes are reported previously as the most stable and efficient delivery system of porphyrin, but their nanostructure converts the singlet oxygen generation mechanism to thermal ablation mechanism. By folate-receptor-mediated endocytosis, folate-porphysomes are internalized into cells rapidly and resulted in efficient disruption of nanostructures, thus switching back on the photodynamic activity of the densely packed porphyrins for effective PDT. In both in vitro and in vivo studies, folate-porphysomes can achieve folate receptor-selective PDT efficacy, which proves the robustness of targeting-triggered PDT activation of porphysome nanostructure for highly selective tumor ablation. The formulation of porphysomes can be modified with other targeting ligands as activatable photosensitizers for personalized treatment in future.

Inherently multimodal nanoparticle-driven tracking and real-time delineation of orthotopic prostate tumors and micrometastases

Prostate cancer is the most common cancer among men and the second cause of male cancer-related deaths. There are currently three critical needs in prostate cancer imaging to personalize cancer treatment: (1) accurate intraprostatic imaging for multiple foci and extra-capsular extent; (2) monitoring local and systemic treatment response and predicting recurrence; and (3) more sensitive imaging of occult prostate cancer bone metastases. Recently, our lab developed porphysomes, inherently multimodal, all-organic nanoparticles with flexible and robust radiochemistry. Herein, we validate the first in vivo application of (64)Cu-porphysomes in clinically relevant orthotopic prostate and bony metastatic cancer models. We demonstrate clear multimodal delineation of orthotopic tumors on both the macro- and the microscopic scales (using both PET and fluorescence) and sensitively detected small bony metastases (<2 mm). The unique and multifaceted properties of porphysomes offers a promising all-in-one prostate cancer imaging agent for tumor detection and treatment response/recurrence monitoring using both radionuclide- and photonic-based strategies.