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Summary The rational design of two-photon absorption (2PA) organic dyes with 2PA cross-section (δ) values tunable by mild stimuli under physiological conditions remains a challenge. Using a simulation-assisted structure screening method, we have designed an acetal terminated distyrylbenzene derivative (Ace-DSB), which can be readily converted into aldehyde terminated molecules (Ald-DSB) to exhibit a significant increase in δ values at 760 nm. The conversion reaction, which dramatically turns on the 2PA absorption capability of the molecules, can occur in an intracellular environment. Furthermore, Ald-DSB exhibits 40 times higher efficiency of two-photon generation of singlet oxygen than Ace-DSB. These turn-on features allow enhanced two-photon laser confocal scanning microscopic imaging and two-photon excited photodynamic therapy (2PE-PDT) for MCF-7 cancer cells and melanoma tumors. This work opens a new avenue toward the design of turn-on-type two-photon absorption molecules for both in vitro and in vivo tumor imaging and 2PA-PDT.

We report the in vivo distribution, toxicity and metabolism of micro-sized fluorescent organic particles and their applications in cerebral blood flow tracing. The fluorescent microparticles exhibit bright fluorescence, good photo-stability and low toxicity; therefore, they are ideal for long-term non-invasive in vivo tracing. In contrast to conventional fluorescent labeling agents, which stain the entire blood vessel, the tracer microparticles can be easily tracked individually and provide vital information about blood flow behavior. Furthermore, we observed stimulated emission from these microparticles in living animals. These microparticles can provide unprecedented contrast for simultaneous observation of the distribution of blood vessels and the dynamics of microcirculation. Pathological examination revealed that the injected microparticles eventually collected in the spleen and liver. We found no observable toxicity of the microparticles to cells or mouse organs. We demonstrate that these fluorescent microparticles are suitable for applications in the field of non-intrusive blood flow tracing and could play a complementary role to traditional imaging agents.

Zn has vital importance to the environment as well as human health. To regulate its dietary ingestion, it is important to monitor its presence in our food and environment, evoking more accurate and more sensitive ways to quantitatively determine its content in the environment. We herein present a squaraine-based chemosensor, namely DMPSQ, which has turn-on fluorescence response toward Zn2+ ion with good linearity, high selectivity and sensitivity down to 80 ppb. Theoretical calculations were also conducted to provide insight to the sensing mechanism and the spectroscopic properties of the compound.

Assisted by theoretical analysis, we designed a small indolic squaraine with δ > 8000 GM at 780 nm, which is ideal for both in vitro and in vivo bio-imaging applications., Small organic dyes with large two-photon absorption (TPA) cross sections (δ) are more desirable in many applications compared with large molecules. Herein, we proposed a facile theoretical method for the fast screening of small organic molecules as potential TPA dyes. This method is based on a theoretical analysis to the natural transition orbitals (NTOs) directly associated with the TPA transition. Experimental results on the small indolic squaraine dyes (ISD) confirmed that their TPA cross sections is strongly correlated to the delocalization degree of the NTOs of the S2 excited states. Aided by this simple and intuitive method, we have successfully designed and synthesized a small indolic squaraine dye (ISD) with a remarkable δ value above 8000 GM at 780 nm. The ISD dye also exhibits a high singlet oxygen generation quantum yield about 0.90. The rationally designed TPA dye was successfully applied in both two-photon excited fluorescence cell imaging and in vivo cerebrovascular blood fluid tracing.

Photovoltaic cells are considered to be one of the most promising renewable energy sources of the 21st century. In particular, dye-sensitized solar cells (DSSCs) and organic photovoltaic devices (OPVs) are potentially the most economical and environmentally friendly ones. Squaraine (SQ) has intense absorption at 600–850 nm, exactly where sun flux is the most abundant. Furthermore, various substituents on SQ cores provide great possibilities for different molecular-design strategies. These characters make SQs ideal candidates for new DSSCs and OPVs. In response to the rapid development of SQ-based solar cells, a panorama of these ongoing studies is presented here, including the general synthetic routes of SQs and the various SQs used in DSSCs and OPVs. Our discussions are focused on the diverse molecular designs of SQs used in DSSCs and OPVs. The design strategies to acquire better light-harvesting abilities are also provided here, as well as the principles behind these strategies.

Photovoltaic cells are considered to be one of the most promising renewable energy sources of the 21st century. In particular, dye-sensitized solar cells (DSSCs) and organic photovoltaic devices (OPVs) are potentially the most economical and environmentally friendly ones. Squaraine (SQ) has intense absorption at 600–850 nm, exactly where sun flux is the most abundant. Furthermore, various substituents on SQ cores provide great possibilities for different molecular-design strategies. These characters make SQs ideal candidates for new DSSCs and OPVs. In response to the rapid development of SQ-based solar cells, a panorama of these ongoing studies is presented here, including the general synthetic routes of SQs and the various SQs used in DSSCs and OPVs. Our discussions are focused on the diverse molecular designs of SQs used in DSSCs and OPVs. The design strategies to acquire better light-harvesting abilities are also provided here, as well as the principles behind these strategies.

The organization of cytoplasmic microtubules during hormone-induced meiotic maturation of goldfish oocytes in vitro was examined by confocal immunofluorescence microscopy using an anti-tubulin antibody. The microtubule network was well distributed in fully grown immature oocytes. Once goldfish oocytes resumed meiotic maturation by a proposed maturation-inducing hormone of this species (17α, 20β-dihydroxy-4-pregnen-3-one, 17α, 20β-DP), cytoplasmic microtubules serially re-organized. Soon after the onset of the germinal vesicle (GV) migration towards the animal pole, the former microtubule network disappeared, followed by the appearance of a long perinuclear tail with high ordered microtubules extending from the vegetal surface of the GV. Incubation of fully grown immature follilces in colcemid, an inhibitor of tubulin polymerization, caused the disappearance of microtubules. However, this treatment did not prevent either the 17α, 20β-DP-induced migration of the GV or GVBD. Coincident with the breakdown of the GV (GVBD), numerous microtubules intruded into the GV from its vegetal surface. Soon after GVBD, a disk-shaped ring consisting of microtubule asters and a small ring with a radial array of microtubules in its center was observed at the animal pole region. In mature oocytes with meiotic spindles at the animal pole surface, cytoplasmic microtubules were concentrated in a small region around the animal pole showing complicated microtubule arrays. The results presented define distinct changes in microtubule organization during the 17α, 20β-DP-induced meiotic maturation of goldfish oocytes.

A new multisignaling molecular probe DFDB was designed for the selective detection of Zn(2+). DFDB can be synthesized by a simple one-step reaction in high yield. Theoretical calculation suggests a novel sandwich structure of the DFDB·Zn(2+) complex.