Through the use of a rhodamine-appended chelate, bpy-Rho, a versatile strategy has been demonstrated to readily form mitochondria-targeting photosensitizers via the incorporation of a variety of luminescent transition-metal systems, M-Rho, such as Re(I), Ir(III), Pt(II), and Rh(III). The emission from the rhodamine singlet excited state and the transition-metal triplet excited state is partially quenched by the depopulation of them into the dark rhodamine triplet excited state. The generation of the triplet excited state of a rhodamine moiety endows the complexes with mitochondria-targeting photosensitizing ability to form singlet oxygen ( 1 O 2 ) for use as a photodynamic therapy (PDT) agent upon visible-light irradiation. The combination of the rhodamine organic dye and luminescent transition-metal centers in such hybrid systems exhibits the synergistic merits for the biological applications, including low dark cytotoxicity, selective tumor cell uptake, high molar absorptivity suitable for low-energy excitation in the visible region, and high photostability. The corresponding in vitro photocytotoxicity and in vivo photo-antitumor efficacy have also been studied to demonstrate the potential PDT application of M-Rho.

The endoplasmic reticulum (ER) is a very important organelle responsible for crucial biosynthetic, sensing, and signalling functions in eukaryotic cells. In this work, we established a strategy of ligand regulation...

A series of pH dependent rhodamine analogs possessing an anilino-methyl moiety was developed and shown to exhibit a unique photophysical response to pH. These Anilinomethylrhodamines (AnMR) maintain a colorless, non-fluorescent spiro-cyclic structure at high pH. The spiro-cyclic structures open in mildly acidic conditions and are weakly fluorescent; however at very low pH, the fluorescence is greatly enhanced. The equilibrium constants of these processes show a linear response to substituent effects, which was demonstrated by the Hammett equation.

A series of fluorescent pH probes based on the spiro-cyclic rhodamine core, aminomethylrhodamines (AMR), was synthesized and the effect of cycloalkane ring size on the acid/base properties of the AMR system was explored. The study involved a series of rhodamine 6G (cAMR6G) and rhodamine B (cAMR) pH probes with cycloalkane ring sizes from C-3 to C-6 on the spiro-cyclic amino group. It is known that the pKa value of cycloalkylamines can be tuned by the different ring sizes in accordance with the Baeyer ring strain theory. Smaller ring amines have lower pKa value, i.e. they're less basic, such that the relative order in cycloalkylamine basicity is: cyclohexyl>cyclopentyl>cyclobutyl>cyclopropyl. Herein, it was found that the pKa values of the cAMR and cAMR6G systems can also be predicted by Baeyer ring strain theory. The pKa values for the cAMR6G series were shown to be higher than the cAMR series by a value of approximately 1.

Recently, small molecule photoacoustic sensors have emerged prominently in chem/biosensing owing to their excellent performance of high contrast, high resolution, and deep penetration depth. However, there has been little report on a photoacoustic sensor for Pd 2+ detection so far. Herein, a ratiometric photoacoustic Pd 2+ sensor, Cy-DPA, based on cyanine fluorophore has been developed. The absorbance peak of Cy-DPA shifts from 710 to 770 nm after the interaction with Pd 2+ , thus producing a strong PA signal output at 770 nm. As-prepared Cy-DPA could sensing palladium with high sensitivity (27 nM) and selectivity in a fast response (<30 s), which opened new avenue for Pd 2+ real-time detection in vivo.P alladium, is mostly inert in the body as a bulk metal.However, there are reports of contact dermatitis when palladium is used in jewelry or dentistry. In addition, palladium is being widely used as a catalyst in organic coupling reactions, for instance, the Heck reaction, 1,2 Stille coupling, 3 the Suzuki reaction, 4,5 Buchwald-Hartwig coupling, 6 and so on. 7 These reactions play an indispensable role in organic synthesis, including medicinal synthesis (such as Gefitinib, Imatinib, and Tebipenem Pivoxil). 8−10 Even after many times of the purification process, there are is still some palladium residue in these medicines. 11,12 Unfortunately, the palladium residue can strongly stimulate the skin and eyes of human and interact with biological macromolecules such as sulfur-containing amino acids, DNA, RNA, protein, and vitamin B 6 after entering into the human body due to their strong complexation. 4,10,13−16 The palladium residue will disturb many normal functions of cells, which will lead to asthma, alopecia, and even abortion. The European Agency for the Evaluation of Medicinal Products has clearly stipulated the threshold of palladium in drugs is 5−10 ppm, and the limit of dietary intake is less than 1.5−15 μg per person per day. 17,18 Therefore, it is necessary to construct an efficient, highly selective, sensitive, and short-time response sensor for detection of palladium.Traditional analytical methods 19 for Pd 2+ detection are generally based on atomic absorption spectrometry (AAS), inductively coupled plasma (ICP), solid phase microextractionhigh-performance liquid chromatography (SPME-HPLC) and X-ray fluorescence (XRF), but these techniques usually require precision instruments, complex sample pretreatment procedures, and strict experimental conditions, making it difficult for real-time monitoring Pd 2+ in living systems. 20,21 Excellent optical sensors for the detection of Pd 2+ seemed to be an ideal

Recently, fluorescent dyes with a structure-inherent mitochondria-targeting capability have obtained great attention as single-molecule self-reporting theranostic agents to distinguish cancer cells from normal cells. However, there was little attempt using these dyes as a self-reporting ligand for cancer-targeted delivery of nanomaterials or drugs for personalized therapy. Herein, we developed a mitochondria-localized multifunctional nanodelivery system for cancer-targeted drug delivery and dual-modal imaging. First, a series of cyanine-structural small molecules with different-charged substituent groups have been screened based on their mitochondria targeting capability. Furthermore, the cyanine-structural molecule with the best mitochondria-targeting ability was decorated on iron oxide nanoparticles (IONP) for dual-modal imaging. The nanoprobes entered into the cancer cell via the organic anion transporting polypeptide (OATP) pathway and anchored on mitochondria due to the strong interaction between the negative mitochondria membrane and the lipophilic cationic cyanine dye. This work opened an avenue using small molecules with structure-inherent-targeting and self-reporting characteristics as a chemical ligand to develop cancer-targeting and subcellular-localized delivery system.

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We report the synthesis, characterization, and photophysical and ion‐binding properties of deep‐red to near‐infrared (NIR) fluorescent rhodamine derivatives, bearing two spirolactone rings and substitution of the oxygen atoms in the xanthene ring with sulfur atoms (1‐S). The diastereoisomeric cis‐ and trans‐forms of the rhodamine derivative were separated and the cis‐form (cis‐1‐S) was structurally characterized by X‐ray crystallography. Upon treatment with Hg2+ ion, cis‐1‐S was converted into the dual spirolactone ring‐opened species, resulting in significant color change and fluorescence enhancement. Substitution of the oxygen atoms with sulfur and extended π‐conjugation across the fused six‐membered rings upon the two rings‐opening processes in the presence of Hg2+ ion led to a significant red‐shift of absorption (623 nm) and fluorescence (706 nm) peaks, compared to the ordinary rhodamine. Furthermore, the intracellular Hg2+‐sensing properties of the cis‐1‐S have been studied by confocal microscopy.