Preparation of near-infrared photoacoustic imaging and photothermal treatment agent for cancer using a modifiable acid-triggered molecular platform.

Ratiometric near-infrared fluorescent pH probes with various pKa values were innovatively designed and synthesized based on cyanine with a diamine moiety. The photochemical properties of these probes were thoroughly evaluated. Among the series, IR-PHA exhibited an optimal pKa value of approximately 6.40, closely matching the pH of cancerous tissues. This feature is particularly valuable for real-time pH monitoring in both living cells and living mice. Moreover, when administered intravenously to tumor-bearing mice, IR-PHA demonstrated rapid and significant enhancement of near-infrared fluorescence and photoacoustic signals within the tumor region. This outcome underscores the probe's exceptional capability for dual-modal cancer imaging utilizing near-infrared fluorescence (NIRF) and photoacoustic (PA) modalities. Concurrently, the application of a continuous-wave near-infrared laser efficiently ablated cancer cells in vivo, attributed to the photothermal effect induced by IR-PHA. The results strongly indicate that IR-PHA is well-suited for NIRF/PA dual-modality imaging and photothermal therapy of tumors. This makes it a promising candidate for theranostic applications involving small molecules.

Covalent RGD-graphene-phthalocyanine nanocomposite for fluorescence imaging-guided dual active/passive tumor-targeted combinatorial phototherapy.

Poor tumor selectivity, low stability and quenched fluorescence are the main challenges to be overcome for nanomedicine, and are mainly caused by the dissociation of the nanostructure and aggregation of chromophores in the biological environment. Herein, covalently connected nanoparticles RGD-graphene-phthalocyanine (RGD-GO-SiPc) were constructed based on RGD peptide, silicon phthalocyanine (SiPc) and graphene oxide (GO) via a conjugation reaction for fluorescence imaging-guided cancer-targeted combinatorial phototherapy. The prepared RGD-GO-SiPc exhibited supreme biological stability, high-contrast fluorescence imaging, significantly enhanced NIR absorption, high photothermal conversion efficiency (25.6%), greatly improved cancer-targeting capability, and synergistic photodynamic (PDT) and photothermal therapy (PTT) efficacy along with low toxicity. Both in vitro and in vivo biological studies showed that RGD-GO-SiPc is a kind of promising multifunctional nanomedicine for fluorescence imaging-guided combined photothermal and photodynamic therapy with dual active/passive tumor-targeting properties.

Dual-Targeting into the Mitochondria of Cancer Cells for Ratiometric Investigation of the Dynamic Fluctuation of Sulfur Dioxide and Formaldehyde with Two-Photon Integrated Semiconducting Polymer Dots.

Mitochondrial sulfur dioxide (SO2) and formaldehyde (FA) in cancer cells serve as important signal molecules in mediating multiple physiological and pathological activities. Accurate monitoring of the dynamic fluctuation of SO2 and FA in the mitochondria of cancer cells is important for insight into their relationships and functions in cancer, understanding cancer mechanism, and the role of mitochondrial homeostasis in cancer invasion and metastasis. Herein, a novel integrated two-photon semiconducting polymer dot (BF@Pdots) with dual-targeting (cancer cells and mitochondrial) and dual-emission in green and red regions, which is rationally designed through a four-step engineering strategy by using two newly synthesized functionalized polymers PFNA and FD-PSMA as precursors, has been developed for accurate tracking of the dynamic variation of SO2 and FA in the mitochondria of cancer cells. The sensing mechanism is on the basis of the fluorescence resonance energy transfer (FRET) process in BF@Pdots tuned by the reversible Michael addition reaction between the sensing-groups and SO2 (or FA). The integrated BF@Pdots nanoprobes display excellent performances in the accurate detection of the dynamic fluctuation of SO2 and FA such as precise positioning in the mitochondria of cancer cells, self-calibrating ratiometric, two-photon emission with long wavelength excitation, and fast reversible response. The BF@Pdots nanoprobes are also applied to the ratiometric detection of the dynamic fluctuation of exogenous and endogenous SO2 and FA in the mitochondria of cancer cells for the first time with satisfactory results. Taken together, this work will provide an attractive way to develop versatile integrated Pdots-based fluorescent probes through flexible molecular engineering for applications in accurate imaging of biomolecules in living systems.

A Tumor-Targeting Near-Infrared Heptamethine Cyanine Photosensitizer with Twisted Molecular Structure for Enhanced Imaging-Guided Cancer Phototherapy.

In recent years, cancer phototherapy has been extensively studied as noninvasive cancer treatment. To present efficient recognition toward cancer cells, most photosensitizers (PSs) are required to couple with tumor-targeted ligands. Interestingly, the heptamethine cyanine IR780 displays an intrinsic tumor-targeted feature even without modification. However, the photothermal efficacy and photostability of IR780 are not sufficient enough for clinical use. Herein, we involve a twisted structure of tetraphenylethene (TPE) between two molecules of IR780 to improve the photothermal conversion efficiency (PCE). The obtained molecule T780T shows strong near-infrared (NIR) fluorescence and improved PCE (38.5%) in the dispersed state. Also, the photothermal stability and ROS generation capability of T780T at the NIR range (808 nm) are both promoted. In the aqueous phase, the T780T was formulated into uniform nanoaggregates (∼200 nm) with extremely low fluorescence and PTT response, which would reduce in vivo imaging background and side effect of PTT response in normal tissues. After intravenous injection into tumor-bearing mice, the T780T nanoaggregates display high tumor accumulation and thus remarkably inhibit the tumor growth. Moreover, the enhanced photostability of the T780T allows for twice irradiation after one injection and leads to more significant tumor inhibition. In summary, our study presents a tumor-targeted small-molecule PS for efficient cancer therapy and brings a new design of heptamethine cyanine PS for potential clinical applications.

Nitrogen, boron-doped Ti3C2 MXene quantum dot-based ratiometric fluorescence sensing platform for point-of-care testing of tetracycline using an enhanced antenna effect by Eu3.

The Ti3C2 MXene quantum dots (Ti3C2 MQDs) derived from Ti3C2 MXene have received much attention because of their remarkable advantages in biosensing. Nevertheless, the functionalization of Ti3C2 MQDs to improve their properties is just in its infant stage. Herein, we firstly synthesized nitrogen and boron co-doped Ti3C2 MQDs (N, B-Ti3C2 MQDs) with good water solubility, strong stability, and high optical characteristics. The N, B-Ti3C2 MQDs exhibit excitation wavelength-dependent blue photoluminescence with optimal excitation/emission peaks at 335/439 nm. Nowadays, the development of fast and real-time detection of tetracycline (TC) in animal derived food is very essential. In this work, a novel point-of-care testing (POCT) platform was established based on ratiometric fluorescence method using N, B-Ti3C2 MQDs coupled with Eu3+. Upon addition of TC in the Eu3+/N, B-MQDs system, blue fluorescence emission of N, B-Ti3C2 MQDs was quenched and red fluorescence emission of Eu3+ was enhanced gradually, which was ascribed to the synergistic inner filter effect and antenna effect. Moreover, we prepared test papers with N, B-Ti3C2 MQDs and Eu3+ for TC detection based on the change of fluorescence color, which could be recognized by color recognizer app installed in the smartphone. Therefore, great promise for POCT of TC is given with the merits of simplicity and visible detection possibility. The proposed method demonstrated a low detection limit of 20 nM. Application of the platform for TC quantification in milk samples opened a novel means for the potential use of N, B-Ti3C2 MQDs in food safety.

An Activatable Near-Infrared Fluorescence Probe for in Vivo Imaging of Acute Kidney Injury by Targeting Phosphatidylserine and Caspase-3.

Renal-clearable and target-responsive near-infrared (NIR) fluorescent imaging probes have been promising for in vivo diagnosis of acute kidney injury (AKI). However, designing an imaging probe that is renal-clearable and concurrently responsive toward multiple molecular targets to facilitate early detection of AKI with improved sensitivity and specificity is challenging. Herein, by leveraging the receptor-mediated binding and retention effect along with enzyme-triggered fluorescence activation, we design and synthesize an activatable small-molecule NIR fluorescent probe (1-DPA2) using a "one-pot sequential click reaction" approach. 1-DPA2 can target both the externalized phosphatidylserine (PS) and active caspase-3 (Casp-3), two essential biomarkers of apoptosis, producing enhanced 808 nm NIR fluorescence and a high signal-to-background ratio (SBR) amenable to detecting the onset of cisplatin-induced AKI in mice as early as 24 h post-treatment with cisplatin. We not only monitor the gradual activation of Casp-3 in the kidney of mice upon AKI progression but also can report on the progressive recovery of kidney functions in AKI mice following N-acetyl-l-cysteine (NAC) therapy via real-time fluorescence imaging by 1-DPA2. This study demonstrates the ability of 1-DPA2 for longitudinal monitoring of renal cell apoptosis by concurrently targeting PS externalization and Casp-3 activation, which is efficient for early diagnosis of AKI and useful for prediction of potential drug nephrotoxicity as well as in vivo screening of anti-AKI drugs' efficacy.

Emissive oxidase-like nanozyme based on an organic molecular cage.

In this study, we introduced four "claw-like" units of dipicolylamine (DPA) to a tetraphenylethylene (TPE)-based organic molecular cage (DPA-TPE-Cage). Coordinated with Zn2+ ions, the obtained ZnDPA-TPE-Cage exhibited aggregation induced emission (AIE) effects and oxidase-like properties, which endowed it with the ability to selectively image and kill Gram-positive bacteria S. aureus efficiently.

A CORM loaded nanoplatform for single NIR light-activated bioimaging, gas therapy, and photothermal therapy in vitro.

Carbon monoxide (CO) can cause mitochondrial dysfunction, inducing apoptosis of cancer cells, which sheds light on a potential alternative for cancer treatment. However, the existing CO-based compounds are inherently limited by their chemical nature, such as high biological toxicity and uncontrolled CO release. Therefore, a nanoplatform - UmPF - that addresses such pain points is urgently in demand. In this study, we have proposed a nanoplatform irradiated by near-infrared (NIR) light to release CO. Iron pentacarbonyl (Fe(CO)5) was loaded in the mesoporous polydopamine layer that was coated on rare-earth upconverting nanoparticles (UCNPs). The absorption wavelength of Fe(CO)5 overlaps with the emission bands of the UCNPs in the UV-visible light range, and therefore the emissions from the UCNPs can be used to incite Fe(CO)5 to control the release of CO. Besides, the catechol groups, which are abundant in the polydopamine structure, serve as an ideal locating spot to chelate with Fe(CO)5; in the meantime, the mesoporous structure of the polydopamine layer improves the loading efficiency of Fe(CO)5 and reduces its biological toxicity. The photothermal effect (PTT) of the polydopamine layer is highly controllable by adjusting the external laser intensity, irradiation time and the thickness of the polydopamine layer. The results illustrate that the combination of CO gas therapy (GT) and polydopamine PTT brought by the final nanoplatform can be synergistic in killing cancer cells in vitro. More importantly, the possible toxic side effects can be effectively prevented from affecting the organism, since CO will not be released in this system without near-infrared light radiation.

The fabrication of transferrin-modified two-photon gold nanoclusters with near-infrared fluorescence and their application in bioimaging.

Transferrin-modified AuNCs (Tf-AuNCs) with two photon-near infrared (TP-NIR) fluorescence were prepared. For the first time, a novel nanoprobe platform, Tf-AuNCs@MnO2, was developed for the TP-NIR fluorescence imaging and magnetic resonance imaging of living cells and tissues. This platform had high spatiotemporal resolution and a tissue-penetration depth of 300 µm.

A red-emissive two-photon fluorescent probe for mitochondrial sodium ions in live tissue.

A cyclocyanine (CC)-based organic small molecule two-photon (TP) fluorescent probe (CCNa1) was developed for mitochondrial sodium ion sensing. CCNa1 exhibits a low solvatochromic shift and strong TP fluorescence enhancement at 575 nm upon binding to Na+ and is insensitive to other metal ions and to pH. CCNa1 demonstrated fast cell loading ability, biocompatibility, and sensitive response to mitochondrial Na+ influx in live cells and mouse brain tissue.

Mechanism of Cyanine5 to Cyanine3 Photoconversion and Its Application for High-Density Single-Particle Tracking in a Living Cell.

Cyanine (Cy) dyes are among the most useful organic fluorophores that have found a wide range of applications in single-molecule and super-resolution imaging as well as in other biophysical studies. However, recent observations that blueshifted derivatives of Cy dyes are formed via photoconversion have raised concerns as to the potential artifacts in multicolor imaging. Here, we report the mechanism for the photoconversion of Cy5 to Cy3 that occurs upon photoexcitation during fluorescent imaging. Our studies show that the formal C2H2 excision from Cy5 occurs mainly through an intermolecular pathway involving a combination of bond cleavage and reconstitution while unambiguously confirming the identity of the fluorescent photoproduct of Cy5 to be Cy3 using various spectroscopic tools. The carbonyl products generated from singlet oxygen-mediated photooxidation of Cy5 undergo a sequence of carbon-carbon bond-breaking and -forming events to bring about the novel dye-to-dye transformation. We also show that the deletion of a two-methine unit from the polymethine chain, which results in the formation of blueshifted products, commonly occurs in other cyanine dyes, such as Alexa Fluor 647 (AF647) and Cyanine5.5. The formation of a blueshifted congener dye can obscure the multicolor fluorescence imaging, leading to misinterpretation of the data. We demonstrate that the potentially deleterious photoconversion, however, can be exploited to develop a new photoactivation method for high-density single-particle tracking in a living cell without using UV illumination and cell-toxic additives.

Survey of X-ray induced Cherenkov excited fluorophores with potential for human use.

X-ray induced molecular luminescence (XML) is a phenomenon that can be utilized for clinical, deep-tissue functional imaging of tailored molecular probes. In this study, a survey of common or clinically approved fluorophores was carried out for their megavoltage X-ray induced excitation and emission characteristics. We find that direct scintillation effects and Cherenkov generation are two possible ways to cause these molecules' excitation. To distinguish the contributions of each excitation mechanism, we exploited the dependency of Cherenkov radiation yield on X-ray energy. The probes were irradiated by constant dose of 6 MV and 18 MV X-ray radiation, and their relative emission intensities and spectra were quantified for each X-ray energy pair. From the ratios of XML, yield for 6 MV and 18 MV irradiation we found that the Cherenkov radiation dominated as an excitation mechanism, except for aluminum phthalocyanine, which exhibited substantial scintillation. The highest emission yields were detected from fluorescein, proflavin and aluminum phthalocyanine, in that order. XML yield was found to be affected by the emission quantum yield, overlap of the fluorescence excitation and Cherenkov emission spectra, scintillation yield. Considering all these factors and XML emission spectrum respective to tissue optical window, aluminum phthalocyanine offers the best XML yield for deep tissue use, while fluorescein and proflavine are most useful for subcutaneous or superficial use.

Natural DNA assisted white light generation and stimuli responsive colour tuning.

The unique structure of a natural nucleic acid, calf thymus DNA, which can provide an appropriate scaffold for an efficient cascaded energy transfer among organic chromophores, has been used for the generation of bright and pure white light on UV light excitation. Two most commonly used DNA stains, 4',6-diamidino-2-phenylindole (DAPI) and ethidium bromide (EB) have been used as a part of the donor-acceptor pairs. We have judiciously selected 10-anthracene-10-yl-3-methylbenzothiazol-3-ium chloride (AnMBTZ), an ultrafast molecular rotor, to act as a bridge between DNA bound DAPI and EB for the cascaded flow of energy. The unique molecular rotor properties of AnMBTZ and its exceptional binding ability with natural DNA help to form a distinct tri-chromophoric system in DNA template which can produce bright and pure white light on UV excitation. Detailed flow of energy from photoexcited DAPI to EB via AnMBTZ has been explored using steady state and time-resolved emission spectroscopy. Further, unique binding nature of AnMBTZ with DNA molecules has been used to modulate the colour of the emission from the present tri-chromophoric system by external stimuli, like salt and temperature. Such unique stimuli responsive multi-chromophoric system in a bio-template has great potential for different lightening applications.

Self-Assembly of an Antitumor Dipeptide Induced Near-Infrared Fluorescence and Improved Stability for Theranostic Applications.

It has been found that the self-assembly of nonfluorescent peptides can generate fluorescent peptide nanoparticles (f-PNPs) to perform multiple functions, including drug delivery and imaging and tracking therapeutic agents. Both pharmacologically inactive peptides and tumor-targeting peptides have been explored to construct biocompatible f-PNPs; however, the application of this technology in delivering antitumor peptides has never been reported. Herein, the self-assembly of an antitumor dipeptide, carnosine, into fluorescent carnosine nanoparticles (f-Car NPs) in the presence of zinc ions is demonstrated. The generated f-Car NPs exhibit fluorescence in the visible and near-infrared (NIR) ranges for fluorescence tracing in vitro and in vivo. On the other hand, the f-Car NPs minimize the contact between the dipeptide and the serum, which overcomes the dipeptide instability resulted from inefficient antitumor activity. In addition, the preparation of f-Car NPs does not introduce extra carrier materials, so the f-Car NPs exhibit biocompatibility to normal fibroblast cells in vitro and negligible toxicity against major organs in vivo. This study provides a new peptide drug delivery strategy with NIR fluorescence tracing ability.

Carbon Dots with Absorption Red-Shifting for Two-Photon Fluorescence Imaging of Tumor Tissue pH and Synergistic Phototherapy.

Phototherapy exhibits significant potential as a novel tumor treatment method, and the development of highly active photosensitizers and photothermal agents has drawn considerable attention. In this work, S and N atom co-doped carbon dots (S,N-CDs) with an absorption redshift effect were prepared by hydrothermal synthesis with lysine, o-phenylenediamine, and sulfuric acid as raw materials. The near-infrared (NIR) absorption features of the S,N-CDs resulted in two-photon (TP) emission, which has been used in TP fluorescence imaging of lysosomes and tumor tissue pH and real-time monitoring of apoptosis during tumor phototherapy, respectively. The obtained heteroatom co-doped CDs can be used not only as an NIR imaging probe but also as an effective photodynamic therapy/photothermal therapy (PDT/PTT) therapeutic agent. The efficiencies of different heteroatom-doped CDs in tumor treatment were compared. It was found that the S,N-CDs showed higher therapeutic efficiency than N-doped CDs, the efficiency of producing 1O2 was 27%, and the photothermal conversion efficiency reached 34.4%. The study provides new insight into the synthesis of carbon-based nanodrugs for synergistic phototherapy and accurate diagnosis of tumors.

Sequential and Switchable Patterning for Studying Cellular Processes under Spatiotemporal Control.

Attachment of adhesive molecules on cell culture surfaces to restrict cell adhesion to defined areas and shapes has been vital for the progress of in vitro research. In currently existing patterning methods, a combination of pattern properties such as stability, precision, specificity, high-throughput outcome, and spatiotemporal control is highly desirable but challenging to achieve. Here, we introduce a versatile and high-throughput covalent photoimmobilization technique, comprising a light-dose-dependent patterning step and a subsequent functionalization of the pattern via click chemistry. This two-step process is feasible on arbitrary surfaces and allows for generation of sustainable patterns and gradients. The method is validated in different biological systems by patterning adhesive ligands on cell-repellent surfaces, thereby constraining the growth and migration of cells to the designated areas. We then implement a sequential photopatterning approach by adding a second switchable patterning step, allowing for spatiotemporal control over two distinct surface patterns. As a proof of concept, we reconstruct the dynamics of the tip/stalk cell switch during angiogenesis. Our results show that the spatiotemporal control provided by our "sequential photopatterning" system is essential for mimicking dynamic biological processes and that our innovative approach has great potential for further applications in cell science.

Trinuclear Organometallic Pt-Ir-Pt Complexes: Insights into Photophysical Properties, Amino Acid Binding and Protein Sensing.

The rational synthesis of trinuclear emissive organometallic complexes with two equivalent platinum(II) centres appended to the ancillary substituted 2,2'-bipyridyl ligand of the cyclometalated iridium(III) centre is reported here. The alkynyl-platinum moiety and cyclometalated iridium(III) centres have been separated through a non-conjugated CH2 -O-CH2 linkage. The emission titration with amino acids reveals that the complexes sense free amino acids. The luminescence sensing of BSA is thus attributed to the amino acid sensing ability of the complexes and confirmed by emission anisotropy and Far-UV CD spectral study. The decrease in α-helix in the CD spectra signifies the changes in the secondary structure of protein in presence of the complexes.

Near-Infrared Photothermal/Photodynamic-in-One Agents Integrated with a Guanidinium-Based Covalent Organic Framework for Intelligent Targeted Imaging-Guided Precision Chemo/PTT/PDT Sterilization.

Phototherapy holds great promise in the treatment of bacterial infections, especially the multidrug resistant bacterial infections. However, most therapeutic agents are based on the integration of individual photothermal agents and photosensitizers, always in the activated state, and generally lack bacterial specificity, resulting in uncertain pharmacokinetics and serious nonspecific damage to normal tissues. Herein, we report a pH-responsive nanoplatform with synergistic chemo-phototherapy function for smart fluorescence imaging-guided precision sterilization. pH reversible activated symmetric cyanine was designed and prepared as a bacterial-specific imaging unit and PTT/PDT-in-one agent. Meanwhile, a guanidinium-based covalent organic framework (COF) was employed as a nanocarrier and chemotherapy agent to build the intelligent nanoplatform via electrostatic self-assembly. The self-assembly of the PTT/PDT-in-one agent and the COF greatly improves the stability and blood circulation of the PTT/PDT-in-one agent and provides charge-reversed intelligent targeting ability. The developed smart nanoplatform not only enables bacterial-targeted imaging but also possesses chemo/PTT/PDT synergetic high-efficiency bactericidal effects with little side effects, showing great potential in practical applications.

Modified Indulines: From Dyestuffs to In Vivo Theranostic Agents.

The efficient, versatile, and straightforward synthesis of the first N-alkyl analogues of induline 3B (8a and 8b) is reported. Thanks to the introduction of lipophilic substituents and their attractive photophysical properties (far-red emission and production of singlet oxygen), phenazinium 8b can be used as a theranostic agent and shows, at very low concentrations (100 nM), a remarkable ability to (i) image cells and zebrafish embryos with high quality under both mono- (514 nm) and biphotonic (790 and 810 nm) excitations, (ii) efficiently and quickly penetrate cancer cells rather than healthy fibroblasts, and (iii) induce a total or almost total cancer cell death in vitro and in vivo after illumination (λexc = 540-560 nm). The molecular structure of 8b is based on a triamino-phenazinium core only, with no need for additional components, highlighting the emergence of a minimalistic and versatile class of fluorescent probes for targeted photodynamic cancer therapy.

Switching on prodrugs using radiotherapy.

Chemotherapy is a powerful tool in the armoury against cancer, but it is fraught with problems due to its global systemic toxicity. Here we report the proof of concept of a chemistry-based strategy, whereby gamma/X-ray irradiation mediates the activation of a cancer prodrug, thereby enabling simultaneous chemo-radiotherapy with radiotherapy locally activating a prodrug. In an initial demonstration, we show the activation of a fluorescent probe using this approach. Expanding on this, we show how sulfonyl azide- and phenyl azide-caged prodrugs of pazopanib and doxorubicin can be liberated using clinically relevant doses of ionizing radiation. This strategy is different to conventional chemo-radiotherapy radiation, where chemo-sensitization of the cancer takes place so that subsequent radiotherapy is more effective. This approach could enable site-directed chemotherapy, rather than systemic chemotherapy, with 'real time' drug decaging at the tumour site. As such, it opens up a new era in targeted and directed chemotherapy.