Studies towards elucidating the potential of 5,10,15,20-tetrakis(p-carboxy-methyleneoxyphenyl)porphyrin as a theranostic agent for applications in PET and PDT

Theranostics with photodynamic therapy for personalized medicine: to see and to treat

Photodynamic Therapy (PDT) is an approved treatment modality, which is presently receiving great attention due to its limited invasiveness, high selectivity and limited susceptibility to drug resistance. Another related research area currently expanding rapidly is the development of novel theranostic agents based on the combination of PDT with different imaging technologies, which allows for both therapy and diagnosis. This combination can help to address issues of suboptimal biodistribution and selectivity through regional imaging, while therapeutic agents enable an effective and personalized therapy. In this review, we describe compounds, whose structures combine PDT photosensitizers with different imaging probes - including examples for near-infrared optical imaging, magnetic resonance imaging (MRI) and nuclear imaging (PET or SPECT), generating novel theranostic drug candidates. We have intentionally focused our attention on novel compounds, which have already been investigated preclinically in vivo in order to demonstrate the potential of such theranostic agents for clinical applications.

Porphyrins as Chelating Agents for Molecular Imaging in Nuclear Medicine

Porphyrin ligands, showing a significant affinity for cancer cells, also have the ability to chelate metallic radioisotopes to form potential diagnostic radiopharmaceuticals. They can be applied in single-photon emission computed tomography (SPECT) and positron emission tomography (PET) to evaluate metabolic changes in the human body for tumor diagnostics. The aim of this paper is to present a short overview of the main metallic radionuclides complexed by porphyrin ligands and used in these techniques. These chelation reactions are discussed in terms of the complexation conditions and kinetics and the complex stability.

ROS-Activated nanoscale coordination polymers for enhanced ultrasound-mediated therapy for the treatment of cancer

Stimuli-responsive nanoplatforms for efficient delivery of drugs in an on-demand manner show promising potential for killing cancer cells with high accuracy and minimal invasiveness. Herein, taking advantage of the good tissue-penetrating depth of sonodynamic therapy (SDT), reactive oxygen species (ROS)-responsive nanoscale coordination polymers (NCPs) were designed through self-assembly of porphyrins (PP) and platinum, which contained ROS-cleavable thioketal (TK) linkers to enhance the release of doxorubicin (Dox) during SDT. Upon exposure to the ultrasound (US), the Dox-loaded NCPs (PTK@PEG/Dox) could generate high amounts of cytotoxic ROS and heat, which not only induced the apoptosis of MCF-7 cells but also facilitated the efficient release of Dox due to the decomposition of the ROS-sensitive TK linkers, achieving the synergistic therapy of US-induced therapy and chemotherapy. After being modified with Arg-Gly-Asp (RGD) peptide, RGD/PTK@PEG exhibited a good targeting ability to cancer cells. Importantly, using the multicellular tumor spheroids (MCTS) derived from MCF-7 cells as a model, the RGD/PTK@PEG/Dox exhibited an efficient and controlled release behavior of Dox under the US irradiation, accompanying a tremendous anti-cancer effect for inducing apoptosis in the solid tumor tissues. This work provided a potential strategy to design controllable and stimuli-responsive nanoplatforms for synergistic/enhanced US-induced cancer therapy. STATEMENT OF SIGNIFICANCE: Stimulus-responsive nanoplatforms can deliver drugs efficiently in an on-demand manner, showing the potential to kill cancer cells with high accuracy and minimal invasiveness. Taking advantage of the good penetration ability of ultrasound (US), nanoscale coordination polymers (NCP) composed of porphyrin (PP), thioketal (TK) linkers, and platinum(II) were prepared via a coordination-driven self-assembly procedure. After doxorubicin (Dox) was loaded on the NCP (PTK@PEG/Dox), the nanoplatform responded to reactive oxygen species (ROS) under the stimulation of US, and induced the on-demand release of Dox, thereby achieving the combined therapeutic effect of sonodynamic therapy (SDT) and chemotherapy for cancer. This work provides a potential strategy for the development of controllable and stimuli-responsive nanoplatforms for enhanced ultrasound-induced cancer therapy.

N-Confused Porphyrin Immobilized on Solid Supports: Synthesis and Metal Ions Sensing Efficacy

In this work, the N-confused porphyrin 5,10,15,20-tetraphenyl-2-aza-21-carbaporphyrin (NCTPP) was immobilized on neutral or cationic supports based on silica and on Merrifield resin. The new materials were characterized by appropriate techniques (UV-Vis spectroscopy, SEM, and zeta potential analysis). Piezoelectric quartz crystal gold electrodes were coated with the different hybrids and their ability to interact with heavy metals was evaluated. The preliminary results obtained showed that the new materials can be explored for metal cations detection and the modification of the material surface is a key factor in tuning the metal selectivity.