Compared with traditional one‐photon fluorescence imaging, two‐photon fluorescence imaging techniques have shown advantages such as increased penetration depth, lower tissue autofluorescence, and reduced photo­damage, and therefore are particularly useful for imaging tissues and animals. In this work, the design and synthesis of two novel DPP‐based compounds with large two‐photon absorption (2PA) cross‐sections (σ ≥ 8100 GM) and aggregation‐induced emission (AIE) properties are reported. The new compounds are red/NIR emissive and show large Stokes shifts (Δλ ≥ 3571 cm−1). 1,2‐Distearoyl‐sn‐glycero‐3‐phosphoethanol amine‐N‐[maleimide(polyethylene glycol)‐2000 (DSPE‐PEG‐Mal) is used as the encapsulation matrix to encapsulate DPP‐2, followed by surface functionalization with cell penetrating peptide (CPP) to yield DPP‐2‐CPP nanoparticles with high brightness, good water dispersibility, and excellent biocompatibility. DPP‐2 nanoparticles have been used for cell imaging and two‐photon imaging with clear visualization of blood vasculature inside mouse ear skin with a depth up to 80 μm.

Live-cell Raman imaging based on bioorthogonal Raman probes with distinct signals in the cellular Raman-silent region (1800–2800 cm−1) has attracted great interest in recent years. We report here a class of water-soluble and biocompatible polydiacetylenes with intrinsic ultrastrong alkyne Raman signals that locate in this region for organelle-targeting live-cell Raman imaging. Using a host-guest topochemical polymerization strategy, we have synthesized a water-soluble and functionalizable master polydiacetylene, namely poly(deca-4,6-diynedioic acid) (PDDA), which possesses significantly enhanced (up to ~104 fold) alkyne vibration compared to conventional alkyne Raman probes. In addition, PDDA can be used as a general platform for multi-functional ultrastrong Raman probes. We achieve high quality live-cell stimulated Raman scattering imaging on the basis of modified PDDA. The polydiacetylene-based Raman probes represent ultrastrong intrinsic Raman imaging agents in the Raman-silent region (without any Raman enhancer), and the flexible functionalization of this material holds great promise for its potential diverse applications.

Spin-orbit charge-transfer intersystem crossing (SOCT-ISC) is useful for the preparation of heavy atom-free triplet photosensitisers( PSs). Herein, as eries of perylene-Bodipy compact electrond onor/acceptor dyads showing efficient SOCT-ISC is prepared. The photophysical properties of the dyads were studiedw ith steady-state and time-resolved spectroscopies. Efficient triplet state formation (quantum yield F T = 60 %) waso bserved, with at riplets tate lifetime (t T = 436 ms) much longert han that accessed with the conventional heavy atom effect (t T = 62 ms). The SOCT-ISC mechanism wasu nambiguously confirmed by direct excitation of the charget ransfer (CT) absorption band by using nanosecond transienta bsorption spectroscopy and time-resolved electronp aramagnetic resonance (TREPR) spectroscopy.T he factors affecting the SOCT-ISC efficiency include the geometry,t he potential energy surfaceo ft he torsion, the spin density for the atoms of the linker,s olvent polarity,a nd the energym atchingo ft he 1 CT/ 3 LE states. Remarkably,t hese heavya tom-free triplet PSs were demonstrated as an ew type of efficient photodynamic therapy (PDT) reagents (phototoxicity,E C 50 = 75 nm), with an egligibled ark toxicity (EC 50 = 78.1 mm)c ompared with the conventionalh eavy atom PSs (dark toxicity,E C 50 = 6.0 mm, light toxicity, EC 50 = 4.0 nm). This study provides in-depthu nderstanding of the SOCT-ISC, unveils the design principles of triplet PSs based on SOCT-ISC, andu nderlines their applicationa sanew generationo fp otent PDT reagents.[a] Dr.[h] Prof. M. Di Donato INO, Istituto Nazionale di Ottica Largo Enrico Fermi 6, 50125F lorence (Italy)[ + + ] These authorscontributed equally to this work.Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

A dual-functional photosensitizer that demonstrates exceptional photodynamic therapy (PDT) efficacy while simultaneously self-monitoring the therapeutic response in real time is reported here. Possessing an ultrahigh 1 O 2 quantum yield of 98.6% in water, the photosensitizer TPCI can efficiently induce cell death in a series of carcinoma cells (IC 50 values less than 300 × 10 −9 m) upon irradiation with an extremely low fluence (460 nm, 4 mW cm −2 for 10 min). In addition, TPCI can self-monitor cell death in real time. It is weakly fluorescent in living cells before irradiation and lights up the nuclei concomitantly with cell death during PDT treatment by binding with chromatin to activate its aggregation-induced emission, attributed to its strong binding affinity with DNA. In vivo studies using mouse models bearing H22 and B16F10 tumor cells validate the ultraefficient PDT efficacy of TPCI as well as the precise real-time noninvasive readout of the tumor response from the beginning of cancer treatment. The dual-functional TPCI serves as an excellent candidate for single-agent photodynamic theranostics, and this work represents a new paradigm for the development of molecules with multiple intrinsic functions for future self-reporting medical applications.in which an AIE-based fluorophore and a photosensitizer are conjugated by tumor-responsive linkers, e.g., caspase-responsive peptides, have been designed for real-time monitoring of PDT therapeutic effects, and have attracted great interest. [9] However, the in vivo application of such conjugates is typically limited in the complicated physiological environment. [10] In addition, the intricate design and sophisticated structures of such conjugates further increase the difficulty in developing them as drugs. Therefore, the development of small molecules that intrinsically combine the dual functions of exceptional noninvasive tumor ablation capability and real-time anticancer efficacy-reporting characteristics would represent an important, but highly challenging, breakthrough.In this study, we designed and synthesized a dual-functional molecule, namely TPCI (Figure 1A), which has exceptional PDT efficacy both in vitro and in vivo. TPCI is water soluble with an ultrahigh singlet oxygen quantum yield of ≈98.6%. In addition to its exceptional PDT efficacy, TPCI can self-report the therapeutic response in real time. It is weakly fluorescent in living cells before irradiation and instantly fluoresces in the nucleus during cell death upon irradiation, which can report the cell death in real time precisely and efficiently. We also validated the in vivo dual-function, single-molecular photodynamic theranostics in mice. TPCI can not only ablate cancer cells efficiently, but also report the anticancer effects in real time from the beginning of therapy.

A compact naphthalenediimide (NDI)–2,2,6,6‐tetramethylpiperidinyloxy (TEMPO) dyad has been prepared with the aim of studying radical‐enhanced intersystem crossing (EISC) and the formation of high spin states as well as electron spin polarization (ESP) dynamics. Compared with the previously reported radical–chromophore dyads, the present system shows a very high triplet state quantum yield (ΦT=74 %), a long‐lived triplet state (τT=8.7 μs), fast EISC (1/kEISC=338 ps), and absorption in the red spectral region. Time‐resolved electron paramagnetic resonance (TREPR) spectroscopy showed that, upon photoexcitation in fluid solution at room temperature, the D0 state of the TEMPO moiety produces strong emissive (E) polarization owing to the quenching of the excited singlet state of NDI by the radical moiety (electron exchange J>0). The emissive polarization then inverts into absorptive (A) polarization within about 3 μs, and then relaxes to a thermal equilibrium while quenching the triplet state of NDI. The formation and decay of the quartet state were also observed. The dyad was used as a three‐spin triplet photosensitizer for triplet–triplet annihilation upconversion (quantum yield ΦUC=2.6 %). Remarkably, when encapsulated into liposomes, the red‐light‐absorbing dyad–liposomes show good biocompatibility and excellent photodynamic therapy efficiency (phototoxicity EC50=3.22 μm), and therefore is a promising candidate for future less toxic and multifunctional photodynamic therapeutic reagents.