The incorporation of intensive light absorbing porphyrins macrocycles with biocompatible nanoparticles would lead to new nanomaterials with multiple imaging and therapeutic modalities. Herein, a facile synthetic strategy has been applied to prepare porphyrin-implanted carbon nanodots (PNDs) by partial and selective pyrolysis of 5,10,15,20-tetrakis­(4-aminophenyl)­porphyrin (TAPP) and citric acid (CA) at an appropriate temperature. As-prepared PNDs exhibit not only the excellent stability and biocompatibility characteristic of carbon nanodots but also the unique properties of porphyrin macrocycle such as strong UV–visible and near-infrared absorption, specifically, high photodynamic therapy efficiency. More importantly, the PNDs with near-infrared absorption could act as a contrast agent for photoacoustic molecular imaging with deep tissue penetration and fine spatial resolution. The Cetuximab-conjugated porphyrin-based carbon nanodots (C225-PNDs) have been further prepared to precisely target the cancer cells (HCC827 and MDA-MB-231 cells) with overexpression of EGFR, leading to highly efficient photodynamic therapy upon two-photo excitation at 800 nm. A complete ablation of tumor together with an enhanced photoacoustic contrast ability for C225-PNDs have been further validated in mice bearing MDA-MB-231 breast cancer.

N-rich metal-free and metal-doped carbon quantum dots (CQDs) have been prepared through one-step hydrothermal method using tetraphenylporphyrin or its transition metal (Pd or Pt) complex as precursor. The structures and morphology of the as-prepared nanoparticles were analyzed by X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectra. Three kinds of nanocomposites show similar structures except for the presence of metal ions in Pd-CQDs and Pt-CQDs indicated by X-ray photoelectron spectroscopy. All of them display bright blue emission upon exposure to ultraviolet irradiation. The CQDs exhibit typical excitation-dependent emission behavior, with the emission quantum yield of 10.1%, 17.8%, and 15.2% for CQDs, Pd-CQDs, and Pt-CQDs, respectively. Moreover, the CQDs, Pd-CQDs, and Pt-CQDs could serve as fluorescent probes for the specific and sensitive detection of Fe 3+ ions in aqueous solution. The low cytotoxicity of CQDs is demonstrated by MTT assay against HeLa cells. Therefore, the CQDs can be used as efficient probes for cellular multicolor imaging and fluorescence sensors for the detection of Fe 3+ ions due to their low toxicity, excellent biocompatibility, and low detection limits. This work provides a new route to synthesize highly luminescent N-rich metal-free or metal-doped CQDs for multifunctional applications.

Near-infrared (NIR)-absorbing organic nanoparticles (ONPs) are emerging candidates for “one-for-all” theranostic nanomaterials with considerations of safety and formulation in mind. However, facile fabrication methods and improvements in the photothermal conversion efficiency (PCE) and photostability are likely needed before a clinically viable set of candidates emerges. Herein, a new organic compound, [porphyrin–diketopyrrolopyrrole (Por–DPP)] with the donor–acceptor structure was synthesized, where porphyrin was used as a donor unit while diketopyrrolopyrrole was used as an acceptor unit. Por–DPP exhibited efficient absorption extending from visible to NIR regions. After self-assembling into nanoparticles (NPs) (∼120 nm), the absorption spectrum of Por–DPP NPs broadened and red-shifted to some extent, relative to that of organic molecules. Furthermore, the architecture of NPs enhanced the acceptor–donor structure, leading to emission quenching and facilitating nonradiative thermal generation. The PCE of Por–DPP NPs was measured and calculated to be 62.5%, higher than most of ONPs. Under 808 nm laser irradiation, the Por–DPP NPs possessed a distinct photothermal therapy (PTT) effect in vitro and can damage cancer cells efficiently in vivo without significant side effects after phototherapy. Thus, the small-molecule porphyrin-based ONPs with high PCE demonstrated promising application in photoacoustic imaging-guided PTT.

Carbon dots (CDs) as an emerging type of carbon nanomaterials exhibit great potential in bioimaging applications owing to their superior optical properties and excellent biocompatibility. However, it is still challenging to fabricate sole carbon dots with integrated functionalities of diagnostic and therapeutic modalities. Herein, we developed a facile strategy to prepare the ruthenium-containing carbon dots (Ru-CDs) via a hydrothermal method using the 5-amino-1,10-phenanthroline ruthenium­(II) complex (Ru-Aphen) and citric acid as starting materials. The structure and morphology of Ru-CDs were verified by transmission electron spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier transform infrared spectra. The Ru-CDs exhibited good water solubility, intense red emission, and efficient reactive oxygen species (ROS) generation. The MTT assay against HeLa cells demonstrated favorable biocompatibility and distinct photodynamic effect of Ru-CDs. Owing to strong luminescence in water (QY = 20.79%) and efficient ROS generation, Ru-CDs were not only applied as bioimaging agents for tumor cells and zebrafish embryos, but also as photodynamic nanoagents for cancer therapy. Finally, the DNA photocleavage of Ru-CDs was verified through the experiment of gel electrophoresis. The results suggested that the plasmid DNA could only be damaged in the presence of Ru-CDs and light. Thus, the as-prepared Ru-CDs showed good prospects and a wide range of biological applications.