One- and Two-Photon Activated Release of Oxaliplatin from a Pt(IV)-Functionalized Poly(phenylene ethynylene)

Light-Responsive Pt(IV) Prodrugs with Controlled Photoactivation and Low Dark Toxicity

Light-induced release of cisplatin from Pt(IV) prodrugs represents a promising approach for precise control over the antiproliferative activity of Pt-based chemotherapeutic drugs. This method has the potential to overcome crucial drawbacks of conventional cisplatin therapy, such as high general toxicity toward healthy organs and tissues. Herein, we report two Pt(IV) prodrugs with BODIPY-based photoactive ligands Pt-1 and Pt-2, which were designed using carbamate and triazole linkers, respectively. Both prodrugs demonstrated the ability to release cisplatin under blue light irradiation without the requirement of an external reducing agent. Dicarboxylated Pt-2 prodrug turned out to be more stable in the dark and more sensitive to light than its monocarbamate Pt-1 counterpart; these observations were explained using DFT calculations. The investigation of the photoreduction mechanism of Pt-1 and Pt-2 prodrugs using DFT modeling and ΔG0 PET estimation suggests that the photoinduced electron transfer from the singlet excited state of the BODIPY axial ligand to the Pt(IV) center is the key step in the light-induced release of cisplatin from the complexes. Cytotoxicity studies demonstrated that both prodrugs were nontoxic in the dark and toxic to MCF-7 cells under low-dose irradiation with blue light, and the observed effect was solely due to the cisplatin release from the Pt(IV) prodrugs. Our research presents an elegant synthetic approach to light-activated Pt(IV) prodrugs and presents findings that may contribute to the future rational design of photoactivatable Pt(IV) prodrugs.

Novel Aggregation-Induced Emission Fluorescent Molecule for Platinum(IV) Ion-Selective Recognition and Imaging of Controlled Release in Cells

The loading, delivery, and release of Pt(IV) precursors in living organisms are important aspects of exploring the development of platinum drugs. In recent years, the biological application of the fluorescent sensors to platinum drugs has been insufficient to meet the study of Pt(IV) precursors. It is urgent to design and develop a biocompatible, multifunctional fluorescent sensor for the study of loading, transport, and release of Pt(IV) ions. Herein, we report a fluorescent molecule (E)-6-(diethylamino)-N'-(4-(diphenylamino) benzylidene)-2-oxo-2H-chromene-3 carbohydrazide (CHTPA). CHTPA has good sensitivity and selectivity to Pt(IV) when the water content is 5%, and significant increase of the fluorescence emission intensity of CHTPA is observed with Pt(IV) concentration. The sensing mechanism is attributed to photo-induced electron transfer, which is verified by X-ray absorption near edge spectroscopy spectra, UV-vis absorption spectroscopy, ¹H NMR spectra, and Fourier transform infrared spectra. Furthermore, the CHTPA-Pt(IV) complex is able to release Pt(IV) in aqueous solution, and the green fluorescence of CHTPA based on the aggregation-induced emission effect can be observed. Inspired by these, the amphiphilic block copolymer poly(ethyloxide)-block-polystyrene (PEO-b-PS) is used to prepare the nonconjugated polymer dots (Pdots). The experimental results show that Pdots can effectively slow down the release speed of Pt(IV) in aqueous solution and it has a great monodispersity in aqueous solution. Meanwhile, Pdots show low cytotoxicity, and this is favorable for intracellular applications. The investigation of cellular imaging indicates that these Pdots can act as a carrier to deliver Pt(IV) into MCF-7 cells for visualized delivery and sustained release of platinum(IV) ions. Therefore, this study provides a new avenue to design and develop a biocompatible multifunctional fluorescent sensor for studying the loading, delivery, and release of Pt(IV) in cells.

Recent Advances in Light-Controlled Activation of Pt(IV) Prodrugs

Pt(IV) prodrugs remain one of the most promising alternatives to conventional Pt(II) therapy due to their versatility in axial ligand choice and delayed mode of action. Selective activation from an external source is especially attractive due to the opportunity to control the activity of an antitumor drug in space and time and avoid damage to normal tissues. In this review, we discuss recent advances in photoabsorber-mediated photocontrollable activation of Pt(IV) prodrugs. Two main approaches developed are the focus of the review. The first one is the photocatalytic strategy based on the flavin derivatives that are not covalently bound to the Pt(IV) substrate. The second one is the conjugation of photoactive molecules with the Pt(II) drug via axial position, yielding dual-action Pt(IV) molecules capable of the controllable release of Pt(II) cytotoxic agents. Thus, Pt(IV) prodrugs with a light-controlled mode of activation are non-toxic in the absence of light, but show high antiproliferative activity when irradiated. The susceptibility of Pt(IV) prodrugs to photoreduction, photoactivation mechanisms, and biological activity is considered in this review.

Functionalization of Water-Soluble Conjugated Polymers for Bioapplications

Water-soluble conjugated polymers (WS-CPs) have found widespread use in bioapplications ranging from in vitro optical sensing to in vivo phototherapy. Modification of WS-CPs with specific molecular functional units is necessary to enable them to interact with biological targets. These targets include proteins, nucleic acids, antibodies, cells, and intracellular components. WS-CPs have been modified with covalently linked sugars, peptides, nucleic acids, biotin, proteins, and other biorecognition elements. The objective of this article is to comprehensively review the various synthetic chemistries that have been used to covalently link biofunctional groups onto WS-CP platforms. These chemistries include amidation, nucleophilic substitution, Click reactions, and conjugate addition. Different types of WS-CP backbones have been used as platforms including poly(fluorene), poly(phenylene ethynylene), polythiophene, poly(phenylenevinylene), and others. Example applications of biofunctionalized WS-CPs are also reviewed. These include examples of protein sensing, flow cytometry labeling, and cancer therapy. The major challenges and future development of functionalized conjugated polymers are also discussed.