Recent Advance in Near‐Infrared (NIR) Imaging Probes for Cancer Theranostics

Nanocrystals for Deep-Tissue In Vivo Luminescence Imaging in the Near-Infrared Region

In vivo imaging technologies have emerged as a powerful tool for both fundamental research and clinical practice. In particular, luminescence imaging in the tissue-transparent near-infrared (NIR, 700-1700 nm) region offers tremendous potential for visualizing biological architectures and pathophysiological events in living subjects with deep tissue penetration and high imaging contrast owing to the reduced light-tissue interactions of absorption, scattering, and autofluorescence. The distinctive quantum effects of nanocrystals have been harnessed to achieve exceptional photophysical properties, establishing them as a promising category of luminescent probes. In this comprehensive review, the interactions between light and biological tissues, as well as the advantages of NIR light for in vivo luminescence imaging, are initially elaborated. Subsequently, we focus on achieving deep tissue penetration and improved imaging contrast by optimizing the performance of nanocrystal fluorophores. The ingenious design strategies of NIR nanocrystal probes are discussed, along with their respective biomedical applications in versatile in vivo luminescence imaging modalities. Finally, thought-provoking reflections on the challenges and prospects for future clinical translation of nanocrystal-based in vivo luminescence imaging in the NIR region are wisely provided.

A novel broadband Ba3Ca4(BO3)3(SiO4)Cl:Mn4+ near-infrared phosphor with a special pseudo-octahedral Mn4+ coordination structure

A pseudo-octahedral coordination structure of Mn4+ has been innovatively designed, which has realized the maximum red shift and the widest full width at half-maximum (FWHM) of Mn4+ emission so far, not only extending the emission wavelength of Mn4+ to the near-infrared (NIR) region, but also effectively broadening its bandwidth. In the Ba3Ca4(BO3)3(SiO4)Cl:Mn4+ (BCBSC:Mn4+) phosphor, the [Mn/Ca1O9] polyhedron contains one [Mn/Ca1O6] octahedron, which constitutes the pseudo-octahedral coordination structure of Mn4+. The BCBSC:Mn4+ phosphor can be excited at 362 nm and 470 nm and exhibits a broadband NIR emission centered at ∼756 nm with a super-wide range from 650 nm to 1100 nm. The FWHM can reach ∼90 nm. In addition, the internal quantum efficiency (IQE) of the BCBSC:0.01Mn4+ phosphor is 69.7%. The unique luminescence characteristics of BCBSC:Mn4+ phosphors are explored using experimental data and first principles calculation. The significant redshift, the abnormal broadband emission, and the high luminous efficiency are closely related to the special highly distorted [Mn/Ca1O6] pseudo-octahedral coordination environment. The results contribute to comprehending the mechanism of the broadband NIR emission of Mn4+ activated phosphors and broaden the research ideas of developing high-performance Mn4+ doped phosphors for NIR phosphor-converted light-emission diode applications.

Formation and fluorescent mechanism of red emissive carbon dots from o-phenylenediamine and catechol system

Carbon dots (CDs) as the advancing fluorescent carbon nanomaterial have superior potential and prospective. However, the ambiguous photoluminescence (PL) mechanism and intricate structure-function relationship become the greatest hindrances in the development and applications of CDs. Herein, red emissive CDs were synthesized in high yield from o-phenylenediamine (oPD) and catechol (CAT). The PL mechanism of the CDs is considered as the molecular state fluorophores because 5,14-dihydroquinoxalino[2,3-b] phenazine (DHQP) is separated and exhibits the same PL properties and behavior as the CDs. These include the peak position and shape of the PL emission and PL excitation and the emission dependence on pH and solvent polarity. Both of them display close PL lifetime decays. Based on these, we deduce that DHQP is the fluorophore of the red emissive CDs and the PL mechanism of CDs is similar to DHQP. During the PL emission of CDs, the electron of the molecule state can transfer to CDs. The formation process of DHQP is further confirmed by the reaction intermediates (phthalazine, dimers) and oPD. These findings provide insights into the PL mechanism of this type of CDs and may guide the further development of tunable CDs for tailored properties.

Fluorescence immunoassay for the targeted determination of trace Listeria monocytogenes based on immunomagnetic separation and CdZnTe quantum dot indication

Infections from invasive Listeria monocytogenes (L. monocytogenes) frequently occur in food and can cause high morbidity and death. Thus, the sensitive, specific, and rapid detection of L. monocytogenes is critical for ensuring food safety and public health. Herein, a fluorescence immunoassay for trace L. monocytogenes detection was designed based on guinea pig antibody-functionalized magnetic nanoparticles (Fe₃O₄ NPs/pAb1) and rabbit antibody-anchored CdZnTe quantum dots (CdZnTe QDs/pAb2). Because of the antibody-directed magnetic separation and long-wave fluorescent emission for CdZnTe QD indication, the constructed immunoassay strategy presented excellent anti-interference performance toward a biological matrix. The immunosensor exhibited a wide detection range of 1 to 10⁹ CFU mL^-1 for L. monocytogenes and a low limit of detection (LOD) of 1 CFU mL^-1, achieving an exceptionally sensitive detection of trace L. monocytogenes. Meanwhile, the immunosensor showed good specificity and had a short time-consumption of 60 min to realize the accurate determination of trace Listeria monocytogenes in spiked tap water and pasteurized milk samples.

Electrochemical Studies of the Cycloaddition Activity of Bismuth(III) Acetylides Towards Organic Azides Under Copper(I)-Catalyzed Conditions

Time-dependent monitoring of the reactive intermediates provides valuable information about the mechanism of a synthetic transformation. However, the process frequently involves intermediates with short lifetimes that significantly challenge the accessibility of the desired kinetic data. We report in situ cyclic voltammetry (CV) and nuclear magnetic resonance (NMR) spectroscopy studies of the cycloaddition reaction of organobismuth(III) compounds with organic azides under the copper(I)-catalyzed conditions. A series of bismuth(III) acetylides carrying diphenyl sulfone scaffolds have been synthesized to study the underlying electronic and steric effects of the tethered moieties capable of transannular oxygen O···Bi interactions and para-functionality of the parent phenylacetylene backbones. While belonging to the family of copper-catalyzed azide-alkyne cycloaddition reactions, the reaction yielding 5-bismuth(III)-triazolide is the sole example of a complex catalytic transformation that features activity of bismuth(III) acetylides towards organic azides under copper(I)-catalyzed conditions. Stepwise continuous monitoring of the copper(I)/copper(0) redox activity of the copper(I) catalyst by cyclic voltammetry provided novel insights into the complex catalytic cycle of the bismuth(III)-triazolide formation. From CV-derived kinetic data, reaction rate parameters of the bismuth(III) acetylides coordination to the copper(I) catalyst (K_A) and equilibrium concentration of the copper species [cat]_eq. are compared with the overall 5-bismuth(III)-triazolide formation rate constant k_obs obtained by ¹H-NMR kinetic analysis.

NIR-II Fluorescent Activatable Drug Delivery Nanoplatform for Cancer-Targeted Combined Photodynamic and Chemotherapy

Nanotheranostics with integrated imaging functions can help monitor nanoparticle accumulation in tumors, thus achieving synergism and higher therapeutic accuracy in cancer therapy. However, it remains challenging to monitor the release of therapeutic drugs in real time from a nanoparticulate drug delivery system (nano-DDS) in the body. Herein, we developed a nano-DDS for fluorescence imaging in the second near-infrared window (NIR-II) region, which can be used for monitoring the responsive release of drugs and cancer-targeted combined photodynamic and chemotherapy. There is a linear correlation between the cumulative release of the drug and the NIR-II fluorescence intensity. Moreover, hyaluronidase/glutathione dual-response RGD-SS-DOX/Ce6@HA-IR-1061 (RSSDCHI) exhibited a higher tumor-to-normal-tissue ratio in NIR-II fluorescence imaging and enhanced antitumor efficacy in vivo. This makes it possible to visualize drug release at the cellular level by the nanocomposites and to predict the treatment effect according to the NIR-II fluorescence intensity in the tumor site, serving as a promising nanoplatform for precision nanomedicine.

Randomized, Double-Blind, Controlled Study to Evaluate Safety and Pharmacokinetics of Single Ascending Doses of ASP5354, an Investigational Imaging Product, in Healthy Adult Volunteers

Intraoperative ureter identification helps reduce the risk of ureteral injury. Currently, no suitable agents for real‐time ureter visualization are approved. ASP5354 (TK‐1) is a novel indocyanine green derivative. In this first‐in‐human phase 1, double‐blind, sequential ascending‐dose study, urethral catheters were placed in 6 healthy volunteers who were randomized to single‐dose, intravenous ASP5354 0.1 mg (n = 4) or placebo (n = 2). Sequential dose escalations to 0.5‐, 2‐, 8‐, and 24‐mg ASP5354 in new cohorts were contingent upon Dose‐Escalation Committee approval after review of pharmacokinetic (PK) and safety data. Blood and urine samples were collected over 24 hours following dose administration. Objectives were to assess the safety/tolerability and PK of ASP5354. Treatment‐emergent adverse events (TEAEs) were reported in 3 (15%) and 2 (20%) participants in the ASP5354 and placebo groups, respectively. In the former, there were 6 TEAEs (5/6 grade 1‐2). One ASP5354 participant experienced grade 3 pyelonephritis, attributed to the catheter. No TEAEs were related to ASP5354. Mean plasma terminal elimination half‐life ranged from 2.1 to 3.6 hours, with near complete urinary excretion of unchanged ASP5354 within 24 hours after administration. Linear and dose‐proportional PK were observed. These results support further evaluation of ASP5354 at doses up to 24 mg for intraoperative near‐infrared fluorescence ureter visualization.

Intraperitoneal Injection of Cyanine-Based Nanomicelles for Enhanced Near-Infrared Fluorescence Imaging and Surgical Navigation in Abdominal Tumors

Fluorescent surgical navigation can effectively aid tumor resection. As one of the most popular near-infrared (NIR) fluorophores, cyanine dye has the outstanding optical ability and the potential to act as a fluorescence probe for tumors. Herein, we report a polyethylene glycol-modified amphiphilic cyanine dye (Cy7-NPC) with an NIR luminescence performance, which can self-assemble to form uniform nanomicelles (Cy7-NPC-S) and which can be applied for the optical imaging of abdominal tumors and for fluorescence imaging-guided precision tumor resection. When applied to biological imaging, Cy7-NPC-S showed high biological safety, strong tissue penetration depth for optical imaging, and high optical imaging resolution. Intraperitoneal administration of Cy7-NPC-S produced remarkable imaging efficacy in abdominal tumors. Compared with intravenous injection, abdominal tumors took up intraperitoneal Cy7-NPC-S faster and in greater quantities, thus enabling Cy7-NPC-S to facilitate accurate recognition and extirpation of abdominal tumors in fluorescence-guided surgery. We believe that metabolizable Cy7-NPC-S with NIR luminescence has promising applications and value in the fields of in vivo imaging and fluorescent surgical navigation.

1550 nm excitation-responsive upconversion nanoparticles to establish dual-photodynamic therapy against pancreatic tumors

The second near-infrared biological window b (NIR-IIb, 1500-1700 nm) is recently considered as the promising region for deeper tissue penetration. Herein, a nanocarrier for 1550 nm light-responsive dual-photodynamic therapy (PDT) is developed to efficiently boost singlet oxygen (1O2) generation. The dual-photosensitizers (PSs), rose bengal (RB) and chlorin e6 (Ce6), are carried by the silica-coated core-shell LiYbF4:Er@LiGdF4 upconversion nanoparticles (UCNPs), forming UCNP/RB,Ce6. Following 1550 nm laser irradiation, the upconversion emission of UCNP/RB,Ce6 in both green (∼550 nm) and red (∼670 nm) colors is fully utilized to activate RB and Ce6, respectively. The simultaneous triggering of dual-PS generates an abundant amount of 1O2 resulting in boosted PDT efficacy. This dual-PDT nanocarrier presents an enhanced anticancer effect under single dose treatment in comparison with the single-PS ones from in vitro and in vivo treatments. The marriage between the boosted dual-PDT and 1550 nm light excitation is anticipated to provide a new avenue for non-invasive therapy.

Biodegradable Silica-Based Nanotheranostics for Precise MRI/NIR-II Fluorescence Imaging and Self-Reinforcing Antitumor Therapy

Multi-modality cancer diagnosis techniques based on the second near-infrared window fluorescence (NIR-II FL, 1000-1700 nm) imaging have become the focus of research attention. For such multimodality probes, how to take advantage of the tumor microenvironments (TME) characteristics to better image diseases and combine efficient therapeutics to achieve theranostics is still a big challenge. Herein, a novel TME-activated nanosystem (FMSN-MnO₂ -BCQ) employing degradable silica-based nanoplatform is designed, adjusting the ratio of intratumoral hydrogen peroxide (H₂ O₂ )/glutathione (GSH) for magnetic resonance imaging (MRI)/NIR-II FL imaging and self-reinforcing chemodynamic therapy (CDT). Innovative bovine serum albumin (BSA)-modified fusiform-like mesoporous silica nanoparticles (FMSN) is fabricated as a carrier for NIR-II small molecule (CQ4T) and MRI reporter MnO₂ . Remarkably, the BSA modification helped to achieve the dual-functions of high biocompatibility and enhance NIR-II fluorescence. The FMSN-MnO₂ -BCQ with FMSN framework featuring a stepwise degradability in tumor interior released MnO₂ and BCQ nanoparticles. Through the specific degradation of MnO₂ by the TME, the produced Mn²⁺ ions are effectively exerted Fenton-like activity to generate hydroxyl radical (•OH) from endogenous H₂ O₂ to eradicate tumor cells. More importantly, the GSH depletion due to the synergistic effect of tetrasulfide bond and MnO₂ in turn induced the oxidative cytotoxicity for self-reinforcing CDT.

Oxygen-Deficient Bimetallic Oxide FeWOX Nanosheets as Peroxidase-Like Nanozyme for Sensing Cancer via Photoacoustic Imaging

Nanozymes with high catalytic activity and great stability have attracted increasing interests as the promising alternative to natural enzymes for applications in various fields. In this study, a new type of highly efficient peroxidase-like nanozymes based on FeWO_X nanosheets (NSs) synthesized by a thermal-decomposition method is reported. Owing to the sheet-structure with maximized utilization of catalytic sites (Fe atoms and oxygen vacancies), such FeWO_X NSs exert efficient enzyme activity to trigger catalytic decomposition of hydrogen peroxide (H₂ O₂ ) into hydroxyl radicals (•OH). A nanozyme-based ratio-metric nanoprobe is then fabricated by co-loading of 3,3,5,5-tetramethylbenzidine (TMB) and IR780 dye on FeWO_X NSs to enable ratio-metric photoacoustic (PA) imaging of endogenous H₂ O₂ , as verified by imaging of the subcutaneous 4T1 xenograft tumor model and lipopolysaccharide (LPS)-induced inflammation model. Moreover, FeWO_X NSs could also be employed as promising nanoagents for multimodal computed tomography (CT) and magnetic resonance (MR) imaging of tumors, due to the strong X-ray attenuation ability of W element and high MR contrast ability of Fe element, respectively. Importantly, FeWO_X NSs with good biodegradability could be cleared out from the body without any significant biotoxicity. This work highlights bimetallic oxide FeWO_X NSs as an enzyme-mimetic nanoplatform for imaging of the tumor microenvironment.

Rational Design of Far-Red to Near-Infrared Emitting Carbon Dots for Ultrafast Lysosomal Polarity Imaging

Carbon dots (CDs) have been widely studied for their excellent properties. However, most of the prepared CDs only show strong emission in the blue to green region, which greatly limits the application of CDs in the biomedical field. In this report, a new design strategy of long-wavelength CDs was reported. The orange phenyl-CDs with good optical properties and biocompatibility were successfully prepared by changing the substituted group of the o-phenylenediamine and the main emission band of phenyl-CDs was in the far-red region. With the increase of polarity, the wavelength of phenyl-CDs red-shifts and the fluorescence intensity decreases, demonstrating their sensitive polarity response function. In addition, phenyl-CDs can achieve ultrafast target imaging of lysosome within 40 s through clathrin-mediated endocytosis. Finally, phenyl-CDs were successfully applied for monitoring lysosomal polarity induced by drugs, which is helpful in getting a better understanding of the physiological and pathological processes of lysosomes. This report provides an important theoretical basis for the rational design and precise synthesis of long-wavelength fluorescent CDs.

CURATE.AI: Optimizing Personalized Medicine with Artificial Intelligence

The clinical team attending to a patient upon a diagnosis is faced with two main questions: what treatment, and at what dose? Clinical trials' results provide the basis for guidance and support for official protocols that clinicians use to base their decisions upon. However, individuals rarely demonstrate the reported response from relevant clinical trials, often the average from a group representing a population or subpopulation. The decision complexity increases with combination treatments where drugs administered together can interact with each other, which is often the case. Additionally, the individual's response to the treatment varies over time with the changes in his or her condition, whether via the indication or physiology. In practice, the drug and the dose selection depend greatly on the medical protocol of the healthcare provider and the medical team's experience. As such, the results are inherently varied and often suboptimal. Big data approaches have emerged as an excellent decision-making support tool, but their application is limited by multiple challenges, the main one being the availability of sufficiently big datasets with good quality, representative information. An alternative approach-phenotypic personalized medicine (PPM)-finds an appropriate drug combination (quadratic phenotypic optimization platform [QPOP]) and an appropriate dosing strategy over time (CURATE.AI) based on small data collected exclusively from the treated individual. PPM-based approaches have demonstrated superior results over the current standard of care. The side effects are limited while the desired output is maximized, which directly translates into improving the length and quality of individuals' lives.

RGD conjugated cell uptake off to on responsive NIR-AZA fluorophores: applications toward intraoperative fluorescence guided surgery

The use of NIR-fluorescence imaging to demarcate tumour boundaries for real-time guidance of their surgical resection has a huge untapped potential. However, fluorescence imaging using molecular fluorophores, even with a targeting biomolecule attached, has a major shortcoming of signal interference from non-specific background fluorescence outside the region of interest. This poor selectivity necessitates prolonged time delays to allow clearance of background fluorophore and retention within the tumour prior to image acquisition. In this report, an innovative approach to overcome this issue is described in which cancer targeted off to on bio-responsive NIR-fluorophores are utilised to switch-on first within the tumour. Bio-responsive cRGD, iRGD and PEG conjugates have been synthesised using activated ester/amine or maleimide/thiol couplings to link targeting and fluorophore components. Their off to on emission responses were measured and compared with an always-on non-responsive control with each bio-responsive derivative showing large fluorescence enhancement values. Live cell imaging experiments using metastatic breast cancer cells confirmed in vitro bio-responsive capabilities. An in vivo assessment of MDA-MB 231 tumour imaging performance for bio-responsive and always-on fluorophores was conducted with monitoring of fluorescence distributions over 96 h. As anticipated, the always-on fluorophore gave an immediate, non-specific and very strong emission throughout whereas the bio-responsive derivatives initially displayed very low fluorescence. All three bio-responsive derivatives switched on within tumours at time points consistent with their conjugated targeting groups. cRGD and iRGD conjugates both had effective tumour turn-on in the first hour, though the cRGD derivative had superior specificity for tumour over the iRGD conjugate. The pegylated derivative had similar switch-on characteristics but over a much longer period, taking 9 h before a significant emission was observable from the tumour. Evidence for in vivo active tumour targeting was obtained for the best performing cRGD bio-responsive NIR-AZA derivative from competitive binding studies. Overall, this cRGD-conjugate has the potential to overcome the inherent drawback of targeted always-on fluorophores requiring prolonged clearance times and shows excellent potential for clinical translation for intraoperative use in fluorescence guided tumour resections.

Orthogonal shortwave infrared emission based on rare earth nanoparticles for interference-free logical codes and bio-imaging

Shortwave infrared (SWIR) photoluminescence has received intense interest in many fields in recent years thanks to the advantages of its wide wavelength range and high tissue imaging ability and it is invisible to the naked eye. However, achieving orthogonal SWIR emission still remains a challenge. In the present study, synthesized NaErF4@NaLuF4 (Er@Lu) and NaYF4:Nd@NaLuF4 (Y:Nd@Lu) nanoparticles emitted atom-like SWIR emission, and the separation distance between the SWIR emission was beyond 50 nm, which permitted orthogonal SWIR signal acquirement with optical filters. Furthermore, an invisible logical code was designed by manipulating the orthogonal SWIR emission of the lanthanide fluoride nanoparticles, and was further operated by basic logical operations and applied in information encryption and anti-counterfeit fields. In addition, the emission between these two hydrophilic nanoparticles could also be separated in vivo without signal interference and the orthogonal SWIR imaging mode was achieved, which was demonstrated in a bio-imaging experiment in vivo. This demonstration extended the orthogonal SWIR emission capacity by controlling the orthogonal emission, opening new opportunities in the fields of data security, disease diagnosis and non-interference label in vivo.

Biocompatible Heat-Shock Protein Inhibitor-Delivered Flowerlike Short-Wave Infrared Nanoprobe for Mild Temperature-Driven Highly Efficient Tumor Ablation

Multifunctional nanomaterials for dual-mode imaging guided cancer therapy are highly desirable in clinical applications. Herein, a flowerlike NiS₂-coated NaLuF₄:Nd (Lu:Nd@NiS₂) nanoparticle was synthesized as a novel therapeutic agent for short-wave infrared light imaging and magnetic resonance imaging to guide photothermal therapy (PTT). The material was then loaded with phenolic epigallocatechin 3-gallate (EGCG), which is a natural heat-shock protein 90 (HSP90) inhibitor. Upon near infrared irradiation, EGCG was released from the Lu:Nd@NiS₂-EGCG, which bound HSP90 and reduced cell tolerance to heat, resulting in a better therapeutic effect at the same elevated temperature. Therefore, with minimal side effects and remarkable antitumor efficacy in vivo, Lu:Nd@NiS₂-EGCG appeared to be a promising photothermal agent for enhanced PTT.