Research Projects

Rationale of Research: Near-infrared (NIR) absorbing dyes (700–2500 nm) can offer dual functionality by enabling both diagnostic imaging and image-guided therapy. For instance, photoacoustic (PA) imaging utilizes NIR light to excite photothermal (PT) agents and detects acoustic waves generated by light-induced thermal expansion to construct high-resolution images. Similarly, photothermal therapy (PTT) employs NIR PT agents to destroy cancer cells by raising the local temperature in tissues. NIR dyes are advantageous due to the ability of light photon to penetrate deep into tissue due to their lower detrimental effects compared to ultraviolet and visible, owing to their lower energy. Thus, this proposal aims to synthesize NIR-III absorbing (1500-2500 nm) fused porphyrinoid dyes using a narrow band gap metalla-carbaporphyrinoid as the substructure. Our design strategy to achieve NIR-III absorbing porphyrinoid dyes is based on unique dπ–pπ orbital mixing between a late transition metal ion (Pt) and the π-orbitals of the ligand. Objective: The principal objectives of this research proposal are: (a) to develop new NIR-III absorbing porphyrinoid dyes, (b) to achieve superior photothermal conversion efficiency (η), and (c) to improve their bioavailability by converting them to zwitterionic form. Experiments: This research involves several work packages (WPs). WP1-Synthesis and chemical characterization of the proposed NIR-III absorbing porphyrinoid dyes. WP2-Photophysical characterization and electrochemical analysis of the NIR-III dyes, along with dependent density functional theory (DFT) calculation to understand the ground and excited state electronic properties of the molecules. WP3-Evaluation of in vitro PT conversion efficiency and photostability. The time constant (τ) for heat transfer will be calculated based on the cooling stage data, which will be used to evaluate photothermal conversion efficiency. Finally, at a later stage, based on the in-vitro findings, their therapeutic efficacy for PPT and PA imaging will be examined with the help of expert collaborator in in-vivo experimentation. Significance: While several NIR-I/NIR-II (700-1500 nm) dyes have been explored for PA imaging and PPT, however, transitioning to the NIR-III region can significantly enhance light penetration, enabling deeper tissue treatment and high-contrast imaging. Both of which remain practical challenges in PA and PTT applications due to a lack of advanced materials capable of absorbing in the NIR-III region. Organic NIR dyes offer many advantages over other classes of NIR materials, such as inorganic nanoparticles and polymer-based PT agents, which often suffer from toxicity and accumulation. These advantages include biocompatibility, low toxicity, and ease of functionalizations. Thus, developing NIR-III porphyrinoid-based dyes as efficient PT agents for PA imaging and PTT represents a significant advancement in both material design and biomedical applications.