Deep learning-enabled fluorescence imaging for surgical guidance: in silico training for oral cancer depth quantification.

Significance: Oral cancer surgery requires accurate margin delineation to balance complete resection with post-operative functionality. Current in vivo fluorescence imaging systems provide two-dimensional margin assessment yet fail to quantify tumor depth prior to resection. Harnessing structured light in combination with deep learning (DL) may provide near real-time three-dimensional margin detection. Aim: A DL-enabled fluorescence spatial frequency domain imaging (SFDI) system trained with in silico tumor models was developed to quantify the depth of oral tumors. Approach: A convolutional neural network was designed to produce tumor depth and concentration maps from SFDI images. Three in silico representations of oral cancer lesions were developed to train the DL architecture: cylinders, spherical harmonics, and composite spherical harmonics (CSHs). Each model was validated with in silico SFDI images of patient-derived tongue tumors, and the CSH model was further validated with optical phantoms. Results: The performance of the CSH model was superior when presented with patient-derived tumors ( P -value < 0.05 ). The CSH model could predict depth and concentration within 0.4 mm and 0.4 µ g / mL , respectively, for in silico tumors with depths less than 10 mm. Conclusions: A DL-enabled SFDI system trained with in silico CSH demonstrates promise in defining the deep margins of oral tumors.

Use of Proximity Ligation Assay to Study Lymphoid Malignancies.

The advent of high-throughput and unbiased proteogenomic screens promises to rapidly advance our understanding of the molecular mechanisms underpinning pathogenesis of lymphoid malignancies. The wealth of data generated from these studies requires methods to rapidly confirm and extend findings into cell line models and primary patient samples. The proximity ligation assay (PLA) is a method that can visualize protein-protein interactions in situ. PLA can capture transient interactions and characterize constituents of stable biomolecular condensates, both of which pose technical difficulties for traditional biochemical and fluorescence imaging techniques.

Tailoring near-infrared amyloid-ß probes with high-affinity and low background based on CN and amphipathic regulatory strategies and in vivo imaging of AD mice.

Amyloid-ß (Aß) species (Aß fibrils and Aß plaques), as one of the typical pathological markers of Alzheimer's disease (AD), plays a crucial role in AD diagnosis. Currently, some near-infrared I (NIR I) Aß probes have been reported in AD diagnosis. However, they still face challenges such as strong background interference and the lack of effective probe design. In this study, we propose molecular design strategy that incorporates CN group and amphiphilic modulation to synthesize a series of amphiphilic NIR I Aß probes, surpassing the commercial probe ThT and ThS. Theoretical calculations indicate that these probes exhibit stronger interaction with amino acid residues in the cavities of Aß. Notably, the probes containing CN group display the ability of binding two distinct sites of Aß, which dramatically enhanced the affinity to Aß species. Furthermore, these probes exhibit minimal fluorescence in aqueous solution and offer ultra-high signal-to-noise ratio (SNR) for in vitro labeling, even in wash-free samples. Finally, the optimal probe DM-V2CN-PYC3 was utilized for in vivo imaging of AD mice, demonstrating its rapid penetration through the blood-brain barrier and labelling to Aß species. Moreover, it enabled long-term monitoring for a duration of 120 min. These results highlight the enhanced affinity and superior performance of the designed NIR I Aß probe for AD diagnosis. The molecular design strategy of CN and amphiphilic modulation presents a promising avenue for the development Aß probes with low background in vivo/in vitro imaging for Aß species.

Sodium Assists Controlled Synthesis of Cubic Rare-Earth Oxyfluorides Nanocrystals for Information Encryption and Near-Infrared-IIb Bioimaging.

Rare-earth oxyfluoride (REOF) colloidal nanocrystals (NCs) suffer from a low photoluminescence efficiency due to their small size with poor crystallinity and a detrimental surface quenching effect. Herein, we introduce an innovative approach that involves doping sodium ions into REOF NCs to produce monodisperse, size-controllable, well-crystallized, and highly luminescent colloidal REOF core/shell NCs. The Na+ doping allows for successfully synthesizing the cubic REOF NCs with a tunable size from 6 to 30 nm. Further fabrication of the core/shell NCs doped with Na+ results in enhancements up to 1062 (Ho3+), 1140 (Er3+), and 2212 (Tm3+) folds in upconversion luminescence and 17.7 folds (Er3+) in downconversion luminescence compared to that of core/shell NCs without doping Na+ ions. These NCs were subsequently developed into multicolor luminescent inks, demonstrating significant potential application for information security, and used for near-infrared-IIb (NIR-IIb) (1500-1700 nm) in vivo imaging, which exhibits a high-resolution in vivo dynamic imaging capability with a signal-to-noise ratio of 5.28. These results present the way to the controlled synthesis of efficient luminescent cubic LuOF: RE3+/LuOF core/shell NCs, expanding the toolkit of rare-earth doped NCs in diverse applications such as advanced encoding encryption, varied fluorescence imaging, and biomedicine.

A chitosan-based near-infrared ratiometric fluorescent nanoprobe created by molecular assembly with applications in hypochlorous acid detection in live mouse.

Hypochlorous acid (HClO/ClO-) is a key reactive oxidative species (ROS) in the body. The HClO/ClO- concentrations are imbalanced during cancer formation due to the ROS stress response. This paper introduces a novel chitosan-based self-calibration fluorescent nanoprobe (ChCyNil) constructed by molecular assembly for the ratiometric detection of HClO/ClO-. Two chromophores with different fluorescence characteristics and HClO/ClO- sensitivity were labeled on chitosan, and nanoparticles were prepared by a self-assembly strategy for HClO/ClO- detection. ChCyNil exhibits several advantages, such as dual near-infrared emissions at 670 nm and 845 nm, tunable fluorescence intensity, self-calibration fluorescence, and good biocompatibility, improving its accuracy in HClO/ClO- detection. Our study confirmed that ChCyNil exhibits a well-assembled spheroidal nanostructure and good photophysical properties in solution. The fluorescence imaging properties were further proved by detecting endogenous HClO/ClO- produced by LPS/PMA stimuli in cells and zebrafish. In addition, ChCyNil was used to detect the fluorescence behavior of HClO/ClO- in tumors of live mice. The successful design and fabrication of ChCyNil have presented a new strategy for constructing detection tools with improved fluorescence properties for HClO/ClO- in live animals.

Enhanced mitochondrial fluorescence imaging through confinement fluorescence effect within a rigid silicon suboxide network.

Fluorescence imaging technology has emerged as a powerful tool for studying intricate mitochondrial morphology within living cells. However, the need for fluorophores with stable fluorescence intensity and low phototoxicity poses significant challenges, particularly for long-term live-cell mitochondrial monitoring. To address this, we introduce the confinement fluorescence effect (CFE) into the design of fluorophores. This strategy involves confining small-molecule fluorophores within a silicon suboxide network structure of nanoparticles (CEF-NPs), which restricts molecular rotation, resulting in the suppression of non-radiative transition and the isolation of encapsulated fluorophores from surrounding quenching factors. CFE-NPs (SY2@SiOx) exhibit exceptional properties, such as high fluorescence intensity (80-fold) and reduced phototoxicity (0.15-fold). Furthermore, the TPP + -functionalized CFE-NPs (SY2@SiOxTPP) demonstrated efficacy in mitochondrial imaging and mitochondrial dynamics monitoring. Biochemistry assays indicated that SY2@SiOxTPP exhibits significantly lower phototoxicity to mitochondrial functions compared to both small-molecule fluorophore and commercial Mito Tracker. This approach allows for the long-term dynamic monitoring of mitochondrial morphological changes through fluorescence imaging, without impairing mitochondrial functionality.

Microplastic retention in green walls for nature-based and decentralized greywater treatment.

In wastewater treatment, two issues have recently received increased attention: nature-based solutions for addressing urban water stress through decentralized treatment and re-use; and emerging pollutants such as microplastics (MPs). At the interface of these, this study investigated living green walls for greywater treatment and their potential for MP removal. A large, pilot-scale green wall was irrigated with greywater (a mix of water collected from laundry, dishwasher, bathroom sinks, and synthetic greywater), and effluent from planted and unplanted sections was compared. MPs >50 µm were analyzed using µRaman spectroscopy and supplementary fluorescence microscopy imaging. The green wall proved efficient for the reduction of chemical oxygen demand (COD) (around 80%), removal of total suspended solids (TSS) (around 90%) and MPs, especially for MPs of the non-polar, hydrophobic polymer type polystyrene and MPs sized 100-500 µm. MP removal was improved in the planted (50-60%) compared to the unplanted section (20%), especially for the size fraction 100-500 µm. Physical filtration by the green wall growing media (a mix of perlite with a grain size of 1-5 mm, and coconut fiber), which was further enhanced by plant roots decreasing the effective pore size, can be considered the most important removal mechanism. Charge-mediated adsorption cannot be expected as MPs and growing media mix were both negatively charged at the prevailing water pH (7-8). Fluorescence imaging for MP analysis, using a merged UV/blue light fluorograph, overestimated MP concentrations in greywater (hundreds of MPs per sample were identified by fluorescence imaging versus tens of MPs by µRaman spectroscopy) and would benefit from further improvement before it can be reliably applied as a cheaper and faster alternative methodology for MP analysis.

Robust Natural Light-Absorbable and -Degradable AIE Photosensitizers for Fluorescence Labeling and Efficient Photodynamic Eradication of Algal Pollutants.

Current water pollution caused by the excessive proliferation of harmful algae urges green methods that can efficiently utilize natural light to treat algal pollution. Herein, a series of aggregation-induced emission (AIE) photosensitizers that can efficiently harness sunshine were synthesized for the environmentally friendly and biocompatible treatment of algal pollution. By tuning the number of thiophene units and the electron conjugation degree, the photosensitizers' absorptions were broadened to cover the whole visible light range. The positive charges guided photosensitizers to aggregate on algal cell surfaces, resulting in a turn-on fluorescence signal and robust reactive oxygen species generation under sunshine, thereby achieving fluorescence labeling and photodynamic eradication of algae. The eradication outcomes demonstrated that the AIE photosensitizers significantly outperformed the commercial algaecide ALG. At 20 ppm photosensitizers, 90.4% and 94.2% killing rates were achieved for C. reinhardtii and C. vulgaris, respectively, 2.8- and 3.6-fold higher than those from the same concentration of ALG. Excellent performances in inhibiting algae growth were also verified with efficiency superior to that of ALG. Importantly, the photosensitizers can self-degrade into biocompatible fragments under irradiation to avoid secondary pollution. The developed photosensitizers that possess sunshine convertibility and degradability provide an efficient tool for algal treatment, showing broad research and application prospects.

Isomerization enhanced fluorescence brightness of benzobisthiadiazole-based NIR-II fluorophores for highly efficient fluorescence imaging: A theoretical perspective.

As a cutting-edge technique, fluorescence imaging in the second near-infrared window (NIR-II) is vital for both biomedical research and clinical applications. However, its intravital imaging capacity has been restricted by the extremely limited brightness of NIR-II fluorophores. To address this challenge, we elucidated the inner mechanism of constructing high-performance NIR-II chromophores based on molecular isomer engineering from detailed computational investigations. Herein, three pairs of cis-trans isomers (cis-1, 2, 3 and trans-1, 2, 3) are designed by attaching amino, methoxyl and nitro moieties to different positions on the donor-acceptor-donor molecular skeleton with benzobisthiadiazole as the acceptor and triphenylamine as the donor. All the compounds feature efficient NIR-II emission ranging in 1000-1164 nm, and the photophysical characterizations are regulated by molecular isomer manipulation. Interestingly, fluorescence quantum yields of cis-isomers are higher than those of their trans-counterparts. These enhancements can be attributed to the significant reduction in non-radiative transition, as evidenced by the non-adiabatic excitation energy, non-adiabatic electron coupling and electron-vibration coupling. Meanwhile, fluorophores with nitro terminal group exhibit superior performance facilitated by the prominently intramolecular charge transfer. As a result, cis-3 achieves an optimal brightness maxima of 196.36 M-1 cm-1 at 632 nm. Notably, the energy gap and the hole-electron related H index are respectively identified as strongly relevant to the emission wavelength and brightness, making them capable of evaluating the feasibility of fluorophores as effective NIR-II candidates. These findings highlight the correlations between molecular geometry and luminescent properties, which will inspire more insights into the development of highly efficient NIR-II fluorophores through rational isomer engineering for biomedical applications.

Classification of tomato seedling chilling injury based on chlorophyll fluorescence imaging and DBO-BiLSTM.

Introduction: Tomatoes are sensitive to low temperatures during their growth process, and low temperatures are one of the main environmental limitations affecting plant growth and development in Northeast China. Chlorophyll fluorescence imaging technology is a powerful tool for evaluating the efficiency of plant photosynthesis, which can detect and reflect the effects that plants are subjected to during the low temperature stress stage, including early chilling injury. Methods: This article primarily utilizes the chlorophyll fluorescence image set of tomato seedlings, applying the dung beetle optimization (DBO) algorithm to enhance the deep learning bidirectional long short term memory (BiLSTM) model, thereby improving the accuracy of classification prediction for chilling injury in tomatoes. Firstly, the proportion of tomato chilling injury areas in chlorophyll fluorescence images was calculated using a threshold segmentation algorithm to classify tomato cold damage into four categories. Then, the features of each type of cold damage image were filtered using SRCC to extract the data with the highest correlation with cold damage. These data served as the training and testing sample set for the BiLSTM model. Finally, DBO algorithm was applied to enhance the deep learning BiLSTM model, and the DBO-BiLSTM model was proposed to improve the prediction performance of tomato seedling category labels. Results: The results showed that the DBO-BiLSTM model optimized by DBO achieved an accuracy, precision, recall, and F1 score with an average of over 95%. Discussion: Compared to the original BiLSTM model, these evaluation parameters improved by 9.09%, 7.02%, 9.16%, and 8.68%, respectively. When compared to the commonly used SVM classification model, the evaluation parameters showed an increase of 6.35%, 7.33%, 6.33%, and 6.5%, respectively. This study was expected to detect early chilling injury through chlorophyll fluorescence imaging, achieve automatic classification and labeling of cold damage data, and lay a research foundation for in-depth research on the cold damage resistance of plants themselves and exploring the application of deep learning classification methods in precision agriculture.

Water-Soluble Lipophilic Near-Infrared Region II Fluorophores for High-Brightness Lipid Layer and Lipid Droplets Imaging Applications.

Fluorescence imaging in the second near-infrared region (NIR-II, 1000-1700 nm) has garnered considerable attention for displaying the biological information of deep tissues. However, the lack of biocompatible contrast agents with bright NIR-II emission has hampered the precise clinical application of deep tissue imaging. Here, a lipophilic enhancement strategy employing donor-acceptor-donor (D-A-D) molecules, introducing long alkoxy chains and quaternary ammonium salts for the development of highly bright water-soluble NIR-II fluorophores (BBTD-2C-N), is described. Notably, liposome-encapsulated BBTD-2C-N nanoparticles (B-2C-N/DMPC) in aqueous solution exhibit a 1.8-fold increase in NIR-II fluorescence brightness compared to free BBTD-2C-N in methanol. Avoidance of the aggregation-caused quenching effect and enhanced NIR-II fluorescence are attributed to significantly attenuated π-π stacking interactions and maintained monodisperses in the hydrophobic liposome shell. Moreover, BBTD-2C-N demonstrates superior performance in visualizing lipid droplet-rich HeLa cells in vitro, as well as precise monitoring of adipose tissue and fatty liver in vivo. This study reveals a new avenue for the development of bright NIR-II fluorophores and precise in vivo imaging.

Tetraalkynylporphyrin-mediated covalent assembly of gold nanoclusters for targeted tumor fluorescence imaging and enhanced photodynamic therapy.

A covalent assembly strategy was developed to construct a gold nanocluster-based nano-assembly (AuNCNA) in a controllable manner, using Au8 nanocluster as node and 5,10,15,20-tetra(4-alkynylphenyl)porphine (TEPP) as ligand. Subsequently, the tripeptide arginine glycine aspartic acid (RGD) peptide is further modified via clicking reaction to build a multi-functional nanoplatform (AuNCNA@RGD) that can integrate the targeted fluorescence imaging and efficient photodynamic therapy (PDT). The strong interregulation of Au8 nanocluster and TEPP results in AuNCNA@RGD exhibiting three distinct advantages: (i) TEPP plays an important role in stabilizing the Au8 nanocluster and keeping the active site fixed within the framework, thereby enhancing stability of Au8 nanocluster; (ii) Au8 nanocluster possess adjustable energy level, which can accelerate the transfer of photogenerated charge and prevent the recombination of electrons and holes, thus improving the photosensitivity of TEPP for PDT; (iii) AuNCNA exhibits bright fluorescence emission that facilitates RGD-assisted targeted tumor imaging. This work expands the construction method of AuNC assembly, and this assembly method is versatile and can flexibly transform different organic ligands to construct various AuNC-based functional nanomaterials.

The Role of Indocyanine Green With Near-Infrared Imaging for the Intraoperative Detection and Enhancement of Endometriosis Lesions: A Narrative Review.

Background: There is a clinical need for improved intraoperative detection of endometriosis, and the use of Indocyanine Green with Near-Infrared Imaging (NIR-ICG) is a novel technique for this purpose. The aim of this review is to determine whether NIR-ICG is an effective tool for endometriosis detection and establish an evidence-based methodology for its use.Methods: This review searches Ovid MEDLINE and Embase through July 2023 and considers primary literature published in English describing the use of NIR-ICG to detect endometriosis intraoperatively. Case studies, video demonstrations and articles describing NIR-ICG used for other surgical roles were not considered. Identified studies were screened independently by two authors, and data was extracted by a single author.Results: NIR-ICG was found to enhance the detection of endometriosis in six out of the nine included studies with additional lesion identification, and to have an unchanged or reduced efficacy compared to current standards in the remaining three. Across all studies there were lesions missed by NIR-ICG which were detected by conventional imaging. A greater duration of time between dye administration and visualisation of lesions was found to be more effective for detection. The ideal ICG protocol proposed from this review is a fixed amount of dye proportional to patient weight prior to surgery (0.25-0.3 mg/kg) followed by a longer waiting time before imaging (10-30 min).Conclusion: NIR-ICG has a possible role to enhance the identification of endometriosis intraoperatively as an adjunct to conventional white light imaging, particularly deeper infiltrating disease. However, substantial further research is required in this field.

Highly integrated, self-powered and activatable bipedal DNA nanowalker for imaging of base excision repair in living cells.

DNA walkers have attracted considerable attention in biosensing and bioimaging. Compared with the conventional single leg-based DNA walker, the bipedal DNA walker has remarkable advantages, with improved sensitivity and fast kinetics, and can work efficiently in a crowded cellular environment. However, most reported bipedal DNA walkers are powered by exogenous supplementation, and elaborate DNA sequence designs, auxiliary additives or extra carriers are often needed. A highly integrated bipedal DNA walker that can address robustness, sensitivity and consistency issues in a single system is highly desirable but remains a great challenge. We herein report a novel bipedal DNA nanowalker system through simple assembly of a DNA substrate, hairpin functionalized-AuNPs (AuNPs-H2), and a blocked Mn2+-dependent DNAzyme hairpin (H1) on degradable MnO2 nanosheets, which holds great potential for living cell operation. Highly integrated features enable the simultaneous delivery of core components of the bipedal DNA walker, including a walking track (AuNPs-H2), a walking strand (H1 cleaved by APE1), and a driving force (Mn2+-dependent DNAzyme cleavage) as a whole, thereby enhancing the control of the spatiotemporal distribution of these components at the intracellular target sites. The redox reaction between the MnO2 nanosheets and GSH inside the cells not only consumed the intracellular GSH to improve the biostability of the walking track but also generated abundant Mn2+ as a cofactor of the DNAzyme. As a proof of concept, the developed nanowalker was demonstrated to work efficiently for monitoring base excision repair (BER)-related human apurinic/apyrimidinic endonuclease 1 (APE1) in living cells, highlighting the great potential of the bipedal DNA nanowalker in biological systems.

Role of Peroxynitrite in the Pathogenesis of Parkinson's Disease and Its Fluorescence Imaging-Based Detection.

Parkinson's disease (PD) is the second most common neurodegenerative disorder, affecting the lives of millions of people worldwide. Although the mechanism underlying PD pathogenesis is largely undefined, increasing evidence indicates that oxidative and nitrosative stresses play a crucial role in PD occurrence and development. Among them, the role of oxidative stress has been widely acknowledged, but there is relatively less attention given to nitrosative stress, which is mainly derived from peroxynitrite. In the present review, after briefly introducing the background of PD, we discuss the physiopathological function of peroxynitrite and especially highlight how overloaded peroxynitrite is involved in PD pathogenesis. Then, we summarize the currently reported fluorescence imaging-based peroxynitrite detection probes. Moreover, we specifically emphasize the probes that have been applied in PD research. Finally, we propose perspectives on how to develop a more applicable peroxynitrite probe and leverage it for PD theranostics. Conclusively, the present review broadens the knowledge on the pathological role of peroxynitrite in the context of PD and sheds light on how to develop and utilize fluorescence imaging-based strategies for peroxynitrite detection.

Clinical and Cost-Effectiveness of Intraoperative Flap Perfusion Assessment With Indocyanine Green Fluorescence Angiography in Breast and Head and Neck Reconstructions: A Systematic Review and Meta-Analysis.

BACKGROUND: Indocyanine green fluorescence angiography (ICGFA) is gaining popularity for the assessment of reconstructive flap perfusion intraoperatively. This study analyses the literature with a focus on its clinical efficacy and cost-effectiveness across various plastic and reconstructive surgery procedures. METHODS: A systematic review was conducted in accordance with PRISMA guidelines on published studies in English comparing ICGFA with standard clinical assessment for flap perfusion. Meta-analysis concerned perfusion-related complications and cost data. RESULTS: Twenty-five studies met the inclusion criteria, of which two were randomized controlled trials (RCTs) and four were prospective cohort studies. Twenty-one studies were AHRQ Standard 'Good'; however, the overall level of evidence remains low. ICGFA was predominantly performed in breast surgeries (n = 3310) and head and neck reconstruction (n = 701) albeit with inconsistency in protocols and predominantly subjective interpretations (only five studies utilized objective thresholds). In breast surgery, meta-analysis demonstrated significant reductions in mastectomy skin flap necrosis (odds ratio (OR) 0.58, p < 0.0001), fat necrosis (OR 0.31, p < 0.001), infection (OR 0.66, p = 0.02), and re-operation (OR 0.40, p < 0.0001), but no significant decrease in total or partial flap loss (OR 0.78, p = 0.57/OR 0.87, p = 0.56, respectively) or increase in dehiscence (OR 1.55, p = 0.11). In head and neck surgery, ICGFA significantly decreased total flap loss (OR 0.47, p = 0.04), although not partial flap loss (OR 0.37, p = 0.13) and reoperation (OR 0.92, p = 0.73). Lower limb (n = 104) and abdominal wall (n = 95) reconstructive surgeries were much less studied with no significant ICGFA impact. Seven studies reported cost savings with flap surgeries and breast reconstructions, although study heterogeneity precluded meta-analysis. CONCLUSIONS: ICGFA appears to be a useful, cost-effective tool to identify otherwise unsuspected hypoperfusion in breast and head and neck reconstruction. There is a clear need for standardization, however, to avoid bias. Further RCTs are necessary to solidify these promising clinical findings.

Rational Design of an Activatable Near-Infrared Fluorogenic Platform for In Vivo Orthotopic Tumor Imaging and Resection.

Rational and effective design of a universal near-infrared (NIR) light-absorbed platform employed to prepare diverse activatable NIR fluorogenic probes for in vivo imaging and the imaging-guided tumor resection remains less exploited but highly meaningful. Herein, mandelic acid with a core structure of 4-hydroxylbenzyl alcohol to link recognition unit, a fluorophore and a quencher was employed to prepare activatable probes. We exemplified ester as carboxylesterase (CE)-recognized unit, ferrocene as quencher and phenothiazinium as NIR fluorophore to afford fluorogenic probes termed NBS-Fe-CE and NBS-C-Fe-CE. These probes enabled the conversion toward CE with significant fluorescence increases and successfully discriminate CE activity in cells. NIR light enhances the tumor penetration and enable imaging-guided orthotopic tumor resection. This specific case demonstrated that this platform can be effectively used to construct diverse NIR probes for imaging analytes in biological systems.

Nitric Oxide-Photodelivering Materials with Multiple Functionalities: From Rational Design to Therapeutic Applications.

The achievement of materials that are able to release therapeutic agents under the control of light stimuli to improve therapeutic efficacy is a significant challenge in health care. Nitric oxide (NO) is one of the most studied molecules in the fascinating realm of biomedical sciences, not only for its crucial role as a gaseous signaling molecule in the human body but also for its great potential as an unconventional therapeutic in a variety of diseases including cancer, bacterial and viral infections, and neurodegeneration. Handling difficulties due to its gaseous nature, reduced region of action due to its short half-life, and strict dependence of the biological effects on its concentration and generation site are critical questions to be solved for appropriate therapeutic uses of NO. Light-activatable NO precursors, namely, NO photodonors (NOPDs), address the above issues since they are stable in the dark and permit in a noninvasive fashion the remote-controlled delivery of NO on demand with great spatiotemporal precision. Engineering biocompatible materials with NOPDs and their combination with additional imaging, therapeutic, and phototherapeutic components leads to intriguing light-responsive multifunctional constructs exhibiting promising potential for biomedical applications. This contribution illustrates the most significant progress made over the last five years in achieving engineered materials including nanoparticles, gels, and thin films, sharing the common feature to deliver NO under the exclusive control of the biocompatible visible/near infrared light inputs. We will highlight the logical design behind the fabrication of these systems, illustrating the potential therapeutic applications with particular emphasis on cancer and bacterial infections.

Biodegradable ICG-Conjugated Germanium Nanoparticles for In Vivo Near-Infrared Dual-Modality Imaging and Photothermal Therapy.

Theranostics, by integrating diagnosis and therapy on a single platform, enables real-time monitoring of tumors during treatment. To improve the accuracy of tumor diagnosis, the fluorescence and photoacoustic imaging modalities can complement each other to achieve high resolution and a deep penetration depth. Despite the superior performance, the biodegradability of theranostic agents plays a critical role in enhancing nanoparticle excretion and reducing chronic toxicity, which is essential for clinical applications. Herein, we synthesize biocompatible and biodegradable indocyanine green (ICG)-conjugated germanium nanoparticles (GeNPs) and investigate their biodistributions in nude mice and 4T1 tumor models after intravenous injections using near-infrared (NIR) dual-modality fluorescence and photoacoustic imaging. The ICG-conjugated GeNPs have strong NIR absorption due to the NIR-absorbing ICG and Ge in combination, emit strong NIR fluorescence due to the multilayered ICG coatings, and exhibit very low in vitro and in vivo toxicity. After tail vein injections, the ICG-conjugated GeNPs mainly accumulate in the liver and spleen as well as the tumor with the help of the enhanced permeability and retention effect. The tumor's fluorescence signal is much stronger than that of the control group injected with pure ICG solution, as the GeNPs can function as biodegradable carriers for efficiently delivering the ICG molecules to the tumor. Lastly, the ICG-conjugated GeNPs accumulated in the tumor can also be utilized for photothermal treatment under NIR laser irradiation, after which the tumor volume almost diminishes after 14 days. The experimental findings in this work demonstrate that the ICG-conjugated GeNPs are promising theranostic agents with exceptional biodegradability for in vivo NIR dual-modality imaging and photothermal therapy.