Zwitterionic Near-infrared Fluorophore Research Articles

HSA-ZW800-PEG for Enhanced Optophysical Stability and Tumor Targeting.

Small molecule fluorophores often face challenges such as short blood half-life, limited physicochemical and optical stability, and poor pharmacokinetics. To overcome these limitations, we conjugated the zwitterionic near-infrared fluorophore ZW800-PEG to human serum albumin (HSA), creating HSA-ZW800-PEG. This conjugation notably improves chemical, physical, and optical stability under physiological conditions, addressing issues commonly encountered with small molecules in biological applications. Additionally, the high molecular weight and extinction coefficient of HSA-ZW800-PEG enhances biodistribution and tumor targeting through the enhanced permeability and retention effect. The unique distribution and elimination dynamics, along with the significantly extended blood half-life of HSA-ZW800-PEG, contribute to improved tumor targetability in both subcutaneous and orthotopic xenograft tumor-bearing animal models. This modification not only influences the pharmacokinetic profile, affecting retention time and clearance patterns, but also enhances bioavailability for targeting tissues. Our study guides further development and optimization of targeted imaging agents and drug-delivery systems.

CD117‐Targeted Intraoperative Imaging of Gastrointestinal Stromal Tumor Using a Stem‐Cell‐Factor‐Labeled Fluorophore

Complete resection without damaging the capsule is the gold‐standard surgical approach for nonmetastatic gastrointestinal stromal tumors (GIST). However, accurately locating tumors during surgery is challenging because GIST is covered by normal mucosal tissue, leading to suboptimal surgeries and increased cancer recurrence rates. To enhance surgical care for GIST, a cutting‐edge near‐infrared (NIR) fluorescent nanoprobe is presented that enables real‐time navigation of GIST by specifically targeting CD117, a protein frequently overexpressed in GIST. By attaching a zwitterionic NIR fluorophore called ZW800‐1C to a CD117 ligand, stem cell factor (SCF), precise targeting is achieved while minimizing nonspecific tissue interactions. In in vitro studies, the high affinity of nanoprobe for CD117‐positive GIST‐T1 cell lines is demonstrated, while exhibiting no binding to CD117‐negative cells or GIST‐5 R cells. In a xenograft model of GIST‐T1 in mice, the nanoprobe produces strong and persistent NIR signals that last over 72 h following a single intravenous injection. Moreover, the nanoprobe successfully detects spontaneous tumors in the cecum of heterozygous Kit K641E mice. In these findings, the promise of CD117‐targeted molecular imaging is highlighted as an intraoperative strategy for GIST. Furthermore, this imaging approach holds potential for early diagnosis, as well as monitoring GIST prognosis before and after surgical resection.

Tumor Targeting with Methotrexate-Conjugated Zwitterionic Near-Infrared Fluorophore for Precise Photothermal Therapy.

Targeted tumor imaging can effectively enable image-guided surgery and precise cancer therapy. Finding the right combination of anticancer drugs and near-infrared (NIR) fluorophores is the key to targeted photothermal cancer treatment. In this study, a tumor-targetable NIR fluorophore conjugate with rapid body clearance was developed for accurate tumor imaging and effective photothermal therapy (PTT). The methotrexate (MTX) and zwitterionic NIR fluorophore conjugate (MTX-ZW) were prepared by conjugating a folate antagonist MTX with an aminated ZW800-1 analog to increase the tumor targetability for NIR laser-based PTT of cancer. The MTX, known as a poor tumor-selective drug, showed high tumor accumulation and rapid background clearance after conjugation with the highly water-soluble zwitterionic NIR fluorophore up to 4 h post-injection. The photothermal energy was generated from the MTX-ZW conjugate to induce necrotic cell death in the targeted tumor site under 808 nm laser irradiation. Compared with the previously reported MTX conjugates, the MTX-ZW conjugate can be a great candidate for targeted tumor imaging and fluorescence-guided photothermal cancer therapy. Therefore, these results provide a strategy for the design of drug-fluorophore conjugates and elaborate therapeutic platforms for cancer phototherapy.

Tumor Targeting by Conjugation of Chlorambucil with Zwitterionic Near-Infrared Fluorophore for Cancer Phototherapy.

Improving the tumor targeting of anticancer drugs to minimize systemic exposure remains challenging. The chemical conjugation of anticancer drugs with various near-infrared (NIR) fluorophores may provide an effective approach to improve NIR laser-induced cancer phototherapy. Towards this end, the selection of NIR fluorophores conjugated with hydrophobic anticancer drugs is an important consideration for targeted cancer photothermal therapy (PTT). In this study, a highly water-soluble zwitterionic NIR fluorophore (ZW800) was prepared to conjugate with a water-insoluble anticancer drug, chlorambucil (CLB), to improve tumor targeting, in vivo biodistribution, and PTT performance. The in vivo results using an HT-29 xenograft mouse model demonstrated that the CLB-ZW800 conjugate not only exhibited high tumor accumulation within 4 h after injection, but also showed rapid body clearance behavior for less systemic toxicity. Furthermore, the tumor tissue targeted by the CLB-ZW800 conjugate was exposed to 808 nm NIR laser irradiation to generate photothermal energy and promote apoptotic cell death for the effective PTT of cancer. Therefore, this study provides a feasible strategy for developing bifunctional PTT agents capable of tumor-targeted imaging and phototherapy by the conjugation of small molecule drugs with the versatile zwitterionic NIR fluorophore.

Rapid Tumor Targeting of Renal-Clearable ZW800-1 Conjugate for Efficient Photothermal Cancer Therapy.

The combination of near-infrared (NIR) fluorophores and photothermal therapy (PTT) provides a new opportunity for safe and effective cancer treatment. However, the precise molecular design of functional NIR fluorophores with desired properties, such as high tumor targetability and low nonspecific uptake, remains challenging. In this study, a renal-clearable NIR fluorophore conjugate with high tumor targetability was developed for efficient photothermal cancer therapy. The isoniazid (INH)–ZW800-1 conjugate (INH–ZW) was synthesized by conjugating an antibiotic drug, INH, with a well-known zwitterionic NIR fluorophore, ZW800-1, to improve in vivo performance and fluorescence-guided cancer phototherapy. INH–ZW not only showed rapid tumor accumulation without nonspecific tissue/organ uptake within 1 h after the injection but also generated thermal energy to induce cancer cell death under NIR laser irradiation. Compared with previously reported ZW800-1 conjugates, INH–ZW preserved the ideal biodistribution of ZW800-1 and facilitated improved tumor targeting and PTT. Together, these results demonstrate that the INH–ZW conjugate has great potential to serve as an effective PTT agent capable of rapid tumor targeting and high renal clearance, with excellent photothermal efficacy.

Near-Infrared Fluorescent Agent for In Vitro Screening of Endometrial Cancer and Precancerous Lesions.

The lack of cytopathologists delays the advancement of screening for endometrial cancer. It was urgent to develop a new dye for rapid diagnosis. Our study aimed to synthesize a targeted folate receptor-α near-infrared (NIR) fluorescent agent, folic acid-zwitterionic NIR fluorophore (ZW-FA), and explore the feasibility for screening of endometrial cancer and precancerous change. Folic acid was conjugated with zwitterionic NIR fluorophore. The preparation of ZW-FA was validated by 1H NMR, mass spectrometric, ultraviolet spectra and fluorescence spectra. ZW-FA was incubated with endometrial cytology samples obtained from patients who underwent dilation and curettage or total hysterectomy. Diagnostic utility was calculated by applying laser confocal microscope, Image-J and statistical models, such as enumeration, receiver operating characteristic curve, logistic regression, support vector machine and decision tree were used. The purity of ZW-FA was > 95% determined by 1H NMR. ZW-FA had the strongest absorption peak at 633 nm in ultraviolet spectra. Photostability of ZW-FA was over 8 hours. In clinical validation, a total of 92 patients were enrolled. The cut-off value of ZW-FA was 49 in enumeration, which was used to distinguish the type of samples. Indicators about diagnostic utility are as follows: sensitivity 90.77%, specificity 62.96%, false-positive rate 37.04%, false-negative rate 9.23%, positive predictive value 85.51% and negative predictive value 73.91%. The samples processed by ZW-FA did not affect further Hematoxylin-Eosin staining and pathological diagnosis. It was an effective cytologic strategy for in vitro diagnosis of endometrial cancer and precancerous change by using ZW-FA.Clinical Trial Registration http://www.chictr.org.cn/index.aspx, identifier ChiCTR1800020123.

Mini-Platform for Off-On Near-Infrared Fluorescence Imaging Using Peptide-Targeting Ligands.

Here, we propose a zwitterionic near-infrared (NIR) fluorophore-tryptophan (Trp) conjugate with a cleavable linker as a minimal-sized versatile platform (MP) for the preparation of peptide ligand-based off-on type molecular probes. The zwitterionic NIR fluorophore in MP undergoes fluorescence quenching via a photoinduced electron transfer mechanism when in close proximity to tryptophan, and nonspecific binding with serum proteins is minimized by the zwitterionicity of the fluorophore. The linker can be cleaved inside cancer cells in response to tumor-associated stimuli. As a proof-of-concept experiment, ATTO655 was covalently linked with Trp via a diarginine linker to form an MP. A cyclic peptide consisting of Arg-Gly-Asp-d-Phe-Lys (cRGD) was used as a cancer-targeting ligand and was conjugated to the MP to form cRGD-MP. The NIR fluorescence of cRGD-MP could be selectively turned on inside the target cancer cells, thereby enabling specific fluorescence imaging of integrin αvβ3-overexpressing cancer cells in vitro and in vivo.

Zwitterionic near-infrared fluorophore for targeted photothermal cancer therapy

Precise photothermal cancer therapy still relies on the development of multifunctional theranostic agents to integrate tumor-specific targeting, imaging, and therapy. In this study, we identified the zwitterionic near-infrared (NIR) fluorophore ZW800-Cl, an analog of the well-known ZW800-1, and found that it preferentially accumulated in tumors in various xenograft models. We have demonstrated that the optical and physicochemical properties of ZW800-Cl are similar to those of ZW800-1, but it has a unique tumor targetability. Since ZW800-Cl showed binding selectivity to cancer cells in vitro, it could be specifically targeted to xenograft models of multiple tumor types, including MCF-7, NCI-H460, and HT-29. The in vivo results of photothermal cancer therapy indicated that the xenograft tumors could be effectively ablated by the combination of ZW800-Cl and an 808 nm laser irradiation. In this regard, our finding may provide a new approach for developing multifunctional cancer theranostic agents, setting them apart from conventional nanoparticles based on inorganic and polymeric materials. Therefore, ZW800-Cl may hold promise as a multifunctional theranostic agent for tumor-targeted imaging and effective photothermal cancer therapy.

Targeted molecular imaging of TLR4 in hepatocellular carcinoma using zwitterionic near-infrared fluorophores.

Tumor-associated macrophages (TAMs) are one of the most abundant immune cell types in solid tumors and implicated in tumor progression. Toll-like receptor 4 (TLR4) is expressed in TAMs and plays a key role in immune surveillance and tumor progression. Therefore, molecular imaging of TLR4 has potential not only for detection of TAM-enriched progressing tumors, but also evaluation of TLR4 expression in tumor microenvironment. Here, we report that near-infrared (NIR) fluorescence imaging can provide a real-time imaging of a syngeneic model of murine hepatocellular carcinoma using targeted strategy against TLR4. We conjugated a zwitterionic NIR fluorophore ZW800-1C with minimal nonspecific tissue interactions to anti-TLR4 antibody and observed its targetability. The bioconjugates showed high affinity to murine macrophages in cell culture and in vivo. Interestingly, we observed predominant NIR signals in the tumor site, which persisted for more than 48 h after single intravenous administration of the bioconjugate. This result suggests that TLR4 targeting combined with NIR fluorescence imaging is a useful tool for cancer imaging. This imaging strategy could be used to detect cancerous tissue with the increased TAM content and evaluate the status of TLR4 signaling in solid tumors, ultimately impacting on the diagnostic and prognostic imaging of human cancers.

A zwitterionic near-infrared fluorophore for real-time ureter identification during laparoscopic abdominopelvic surgery

Iatrogenic injury of the ureters is a feared complication of abdominal surgery. Zwitterionic near-infrared fluorophores are molecules with geometrically-balanced, electrically-neutral surface charge, which leads to renal-exclusive clearance and ultralow non-specific background binding. Such molecules could solve the ureter mapping problem by providing real-time anatomic and functional imaging, even through intact peritoneum. Here we present the first-in-human experience of this chemical class, as well as the efficacy study in patients undergoing laparoscopic abdominopelvic surgery. The zwitterionic near-infrared fluorophore ZW800-1 is safe, has pharmacokinetic properties consistent with an ideal blood pool agent, and rapid elimination into urine after a single low-dose intravenous injection. Visualization of structure and function of the ureters starts within minutes after ZW800-1 injection and lasts several hours. Zwitterionic near-infrared fluorophores add value during laparoscopic abdominopelvic surgeries and could potentially decrease iatrogenic urethral injury. Moreover, ZW800-1 is engineered for one-step covalent conjugatability, creating possibilities for developing novel targeted ligands.

Real‐Time Imaging of Vaccine Biodistribution Using Zwitterionic NIR Nanoparticles

Efficient and timely delivery of vaccine antigens to the secondary lymphoid tissue is crucial to induce protective immune responses by vaccination. However, determining the longitudinal biodistribution of injected vaccines in the body has been a challenge. Here, the near-infrared (NIR) fluorescence imaging is reported that can efficiently enable the trafficking and biodistribution of vaccines in real time. Zwitterionic NIR fluorophores are conjugated on the surface of model vaccines and tracked the fate of bioconjugated vaccines after intradermal administration. Using an NIR fluorescence imaging system, it is possible to obtain time-course imaging of vaccine trafficking through the lymphatics, observing notable uptake in lymph nodes with minimal nonspecific tissue interactions. Flow cytometry analysis confirmed that the uptake in lymph nodes by antigen presenting cells was highly dependent on the hydrodynamic diameter of vaccines. These results demonstrate that the combination of a real-time NIR fluorescence imaging system and zwitterionic fluorophores is a powerful tool to determine the fate of vaccine antigens. Since such non-specific vaccine uptake causes serious adverse reactions, this method is not only useful for optimization of vaccine design, but also for safety evaluation of clinical vaccine candidates.

Zwitterionic near-infrared fluorophore-conjugated epidermal growth factor for fast, real-time, and target-cell-specific cancer imaging.

Epidermal growth factor receptor (EGFR) is overexpressed in many types of cancers, which is associated with metastatic potential and poor prognosis in cancer patients. Therefore, development of EGFR-targeted sensitive imaging probes has been a challenge in tumor targeting, image-guided cancer surgery, patient-selective anti-EGFR therapy, and efficient targeted therapies.Methods: We synthesized a zwitterionic near-infrared fluorophore (ATTO655)-conjugated epidermal growth factor (EGF) as a novel activatable molecular probe. Fluorescence OFF/ON property and EGFR-targeting specificity of EGF-ATTO655 as well as its utility in real-time near-infrared (NIR) fluorescence imaging of EGFR-positive cancers were evaluated using in vitro and in vivo studies.Results: When conjugated to EGF, the fluorescence of ATTO655 quenched efficiently by photo-induced electron transfer (PET) mechanism between the conjugated dyes and nearby amino acid quenchers (tryptophan/tyrosine residues), which was stably maintained at physiological pH and in the presence of serum for at least 17 h. The fluorescence of EGF-ATTO655 turned on by receptor-mediated endocytosis and subsequent disintegration of EGF in EGFR-positive A431 cancer cells, thereby enabling specific and real-time fluorescence imaging of EGFR-positive cancer cells. Consequently, EGFR-positive tumors could be clearly visualized 3 h post-injection with a significantly high tumor-to-background ratio (TBR = 6.37).Conclusion: This PET mechanism-based OFF/ON type of EGF probe showed great potential for rapid, real-time, and target-cell-specific imaging of EGFR-overexpressing cancers in vitro and in vivo.

Renally‐Clearable Polymeric Nanochelator for Iron Overload Therapy

Iron (Fe) is an essential metal, but high Fe stores are toxic and cause heart and liver failures, arthritis, and diabetes. Since there is no recognized active pathway for Fe excretion, disposing extra Fe from the body is the primary therapeutic goal of treating patients with iron overload (IO). While the chelation therapy has been widely used to alleviate IO, Fe chelators have serious adverse effects, such as hypotension, gastrointestinal bleeding, kidney failure and liver fibrosis, likely due to non‐specific distribution in off‐target tissues. Consequently, there is an unmet need for a new therapeutic strategy for IO. Here we developed an ultrasmall nanoparticle (NP) that covalently binds to an FDA‐approved Fe chelator deferoxamine (DFO), which limits the distribution into off‐target tissues, while efficiently capturing excess Fe. We first generated renally‐clearable ɛ‐poly‐L‐lysine (EPL) conjugated with zwitterionic near‐infrared fluorophore ZW800. We then produced DFO‐coated NP by conjugating four DFO molecules on the surface of each EPL with balanced charges (DFO4‐NP). The ferrozine competition assay demonstrated that the association constant of DFO4‐NP to Fe was greater by a 3.5‐fold (p<0.001) compared to native DFO, indicating improved Fe binding affinity after conjugation. Next, in vivo chelation efficacy of DFO4‐NP (2 μmol as NP/kg) was determined in IO mice induced by intraperitoneal injection of Fe dextran (100 mg/kg). Urinary Fe content collected over 4 h post‐dose was increased by a 2.5‐fold (p<0.001) and by an 8.6‐fold (p<0.001) after intravenous (i.v.) and subcutaneous (s.c.) injection of DFO4‐NP, respectively, compared to blank NP. Similarly, renal clearance of Fe was increased by a 2.8‐fold (p<0.001) and a 9.5‐fold (p<0.001) after i.v. and s.c. of DFO4‐NP, respectively, compared to NP alone. Moreover, when compared to equimolar dose of native DFO, DFO4‐NP showed increased urinary recovery and renal clearance of Fe by a 2.8‐fold (p=0.003) and by a 2.5‐fold (p=0.003), respectively. These suggest the greater chelation efficiency and urinary excretion of Fe by s.c. DFO‐NP administration than by native DFO or blank NP. We further evaluated the efficacy of DFO4‐NP after s.c. doses daily for 5 d in dietary IO mice. DFO4‐NP decreased non‐heme Fe content in serum (22%, p=0.010), liver (26%, p=0.011) and spleen (26%, p=0.011) compared to blank NP. Consistently, DFO4‐NP decreased the status of an Fe‐storage protein ferritin (Ftn), a reliable marker of body Fe stores, in both liver (28%, p=0.041) and spleen (35%, p=0.024), compared to blank NP. These results indicate that DFO‐NPs efficiently remove excess Fe stores from plasma and tissues after repeated administrations. Moreover, H&E staining showed a decreased density of tubular cells in the kidney after native DFO treatment, while no kidney damage was observed in mice treated with NP alone or DFO4‐NP. Taken together, the renally‐clearable DFO‐NPs provide improved therapeutic efficacy against physiological complications resulting from IO disorders, while minimizing the inherent toxicity of small molecule chelators.Support or Funding InformationNIH U54 HL119145, American Heart Association17GRNT33460134This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

ZW800-1 for Assessment of Blood-Brain Barrier Disruption in a Photothrombotic Stroke Model.

Background: Since it is known that serum albumin-bound dyes can cross the blood-brain barrier (BBB) after ischemia, Evans Blue dye is commonly used to assess BBB disruption because of its rapid binding to serum albumin. In addition, indocyanine green (ICG), a clinically available dye, binds to serum proteins that could also be used for assessment of BBB impairment. Unlike these near-infrared (NIR) dyes, zwitterionic NIR fluorophore (ZW800-1) shows no serum binding, ultralow non-specific tissue uptake, and rapid elimination from the body via renal filtration. In this study, we report the use of ZW800-1 as a NIR fluorescence imaging agent for detecting BBB disruption in rat stroke models.Methods: Three types of NIR fluorophores, Evans Blue, ICG, and ZW800-1, were administered intraperitoneally into rat photothrombotic stroke models by using 4% concentration of each NIR dye. The NIR fluorescence signals in the infarcted brain tissue and biodistribution were observed in real-time using the Mini-FLARE® imaging system up to 24 h post-injection.Results: ZW800-1 provided successful visualization of the ischemic injury site in the brain tissue, while the remaining injected dye was clearly excreted from the body within a certain period of time. Although Evans Blue and ICG provided mapping of the infarcted brain lesions, they exhibited high non-specific uptake in most of the tissues and organs and persisted in the body over 24 h post-injection.Conclusion: Our results suggest the promising application of ZW800-1 as a new strategy in BBB experiments and future therapeutic development.

Targeted zwitterionic near-infrared fluorophores for improved optical imaging

The signal-to-background ratio (SBR) is the key determinant of sensitivity, detectability and linearity in optical imaging. As signal strength is often constrained by fundamental limits, background reduction becomes an important approach for improving the SBR. We recently reported that a zwitterionic near-infrared (NIR) fluorophore, ZW800-1, exhibits low background. Here we show that this fluorophore provides a much-improved SBR when targeted to cancer cells or proteins by conjugation with a cyclic RGD peptide, fibrinogen or antibodies. ZW800-1 outperforms the commercially available NIR fluorophores IRDye800-CW and Cy5.5 in vitro for immunocytometry, histopathology and immunoblotting and in vivo for image-guided surgery. In tumor model systems, a tumor-to-background ratio of 17.2 is achieved at 4 h after injection of ZW800-1 conjugated to cRGD compared to ratios of 5.1 with IRDye800-CW and 2.7 with Cy5.5. Our results suggest that introducing zwitterionic properties into targeted fluorophores may be a general strategy for improving the SBR in diagnostic and therapeutic applications.

Real-Time Simultaneous Near-Infrared Fluorescence Imaging of Bile Duct and Arterial Anatomy

We hypothesized that two independent wavelengths of near-infrared (NIR) fluorescent light could be used to identify bile ducts and hepatic arteries simultaneously, and intraoperatively. Three different combinations of 700 and 800 nm fluorescent contrast agents specific for bile ducts and arteries were injected into N = 10 35-kg female Yorkshire pigs intravenously. Combination 1 (C-1) was methylene blue (MB) for arterial imaging and indocyanine green (ICG) for bile duct imaging. Combination 2 (C-2) was ICG for arterial imaging and MB for bile duct imaging. Combination 3 (C-3) was a newly developed, zwitterionic NIR fluorophore ZW800-1 for arterial imaging and MB for bile duct imaging. Open and minimally invasive surgeries were imaged using the fluorescence-assisted resection and exploration (FLARE) surgical imaging system and minimally invasive FLARE (m-FLARE) imaging systems, respectively. Although the desired bile duct and arterial anatomy could be imaged with contrast-to-background ratios (CBRs) ≥ 6 using all three combinations, each one differed significantly in terms of repetition and prolonged imaging. ICG injection resulted in high CBR of the liver and common bile duct (CBD) and prolonged imaging time (120 min) of the CBD (C-1). However, because ICG also resulted in high background of liver and CBD relative to arteries, ICG produced a lower arterial CBR (C-2) at some time points. C-3 provided the best overall performance, although C-2, which is clinically available, did enable effective laparoscopy. We demonstrate that dual-channel NIR fluorescence imaging provides simultaneous, real-time, and high resolution identification of bile ducts and hepatic arteries during biliary tract surgery.

Synthesis and in vivo fate of zwitterionic near-infrared fluorophores.

To address two fundamental and unsolved problems in optical imaging (nonspecific uptake of near-infrared fluorophores by normal tissues and organs and incomplete elimination of unbound targeted fluorophores from the body), novel zwitterionic near-infrared fluorophores (e.g., ZW800-1) were synthesized and their performance compared in vivo to conventional molecules (e.g., ICG) as a function of charge, charge distribution, and hydrophobicity (see picture).