Optical Contrast Agents Research Articles

Theranostic dye entrapped in an optimized blended-polymer matrix for effective photodynamic inactivation of diseased cells.

Despite the wide range of treatment options available for cancer therapy, including chemotherapy, radiation therapy, and surgical procedures, each of these treatments has a different side-effect profile and leaves the patient with no option but to choose. Due to their insensitivity and nonspecificity, conventional treatments damage normal cells together with cancer cells. In recent years, a significant amount of attention has been focused on photodynamic therapy (PDT) as a treatment for cancer and drug-resistant microbes. An activated photosensitizer is used as a part of the procedure along with oxygen molecules and a specific wavelength of light belonging to the visible or NIR spectral zone. A light-sensitive laser dye, rhodamine 6G (R6G), was used in the present study as a photosensitizer, taking a challenge to improve the aqueous solubility and ROS quantum yield using optimum concentration (160mg/ml) of chitosan-alginate (Cs-Alg) blended polymeric nanoformulations. As evidenced by steady-state spectrophotometric and fluorometric measurements, ROS quantum yield increases three-fold over aqueous solution along with solubility gaining that was validated by PDT experiment using human epithelial carcinoma (KB) cell line. Phantom optical imaging was taken using the IVIS imaging system to establish the formulations as a fluorescence-based optical contrast agent, and zebrafish embryos were used to establish their safe in vivo use. The release profile of R6G was fitted using kinetic models, which followed the Non-Fickian kinetic profile. In conclusion, we recommend the formulations as a potential theranostic agent that will aid in PDT-based therapy in conjunction with optical imaging-based diagnosis.

A Phase 2 Multicenter Clinical Trial of Intraoperative Molecular Imaging of Lung Cancer with a pH-Activatable Nanoprobe.

Intraoperative molecular imaging (IMI) uses tumor-targeted optical contrast agents to improve identification and clearance of cancer. Recently, a probe has been developed that only fluoresces when activated in an acidic pH, which is common to many malignancies. We report the first multicenter Phase 2 trial of a pH-activatable nanoprobe (pegsitacianine, ONM-100) for IMI of lung cancer. Patients with suspected or biopsy-confirmed lung cancer scheduled for sublobar resection were administered a single intravenous infusion of pegsitacianine (1mg/kg) one to three days prior to surgery. Intraoperatively, the patients underwent a white light thoracoscopic evaluation, and then were imaged with an NIR thoracoscope to detect tumor fluorescence. The primary study endpoint was the proportion of patients with a clinically significant event (CSE) which was defined as an intraoperative discovery during IMI that led to a change in the surgical procedure. Possible CSEs included (i) localizing the index lung nodule that could not be located by white light, (ii) identifying a synchronous malignant lesion, or (iii) recognizing a close surgical margin (< = 10mm). Secondary endpoints were sensitivity, specificity, NPV, and PPV of pegsitacianine in detecting tumor-containing tissue. The safety evaluation was based on adverse event reporting, clinical laboratory parameters, and physical examinations. Twenty patients were confirmed as eligible and administered pegsitacianine. Most of the patients were female (n = 12 [60%]), middle-aged (mean age 63.4years), and former smokers (n = 13 [65%], 28.6 mean pack years). Mean lesion size was 1.9cm, and most lesions (n = 17 [85%]) were malignant. The most common histologic subtype was adenocarcinoma (n = 9). By utilizing IMI with pegsitacianine, one patient had a CSE in the detection of a close margin and another had localization of a tumor not detectable by traditional surgical means. Six of 19 (31.6%) malignant lesions fluoresced with mean tumor-to-background ratio (TBR) of 3.00, as compared to TBR of 1.20 for benign lesions (n = 3). Sensitivity and specificity of pegsitacianine-based IMI for detecting malignant tissue was 31.6% and 33.3%, respectively. Positive predictive value (PPV) and negative predictive value (NPV) of pegsitacianine-based IMI was 75% and 7.1%, respectively. Pegsitacianine-based imaging was not effective in differentiating benign and malignant lymph nodes. From a safety perspective, no drug-related serious adverse events occurred. Four patients experienced mild pegsitacianine-related infusion reactions which required discontinuing the study drug with complete resolution of symptoms. Pegsitacianine-based IMI, though well tolerated from a safety perspective, does not consistently label lung tumors during resection and does not provide significant clinical benefit over existing standards of surgical care. The biology of lung tumors may not be as acidic as other solid tumors in the body thereby not activating the probe as predicted.

Injectable Thermogelling Nanostructured Ink as Simultaneous Optical and Magnetic Resonance Imaging Contrast Agent for Image-Guided Surgery.

The development of efficient and biocompatible contrast agents is particularly urgent for modern clinical surgery. Nanostructured materials raised great interest as contrast agents for different imaging techniques, for which essential features are high contrasts, and in the case of precise clinical surgery, minimization of the signal spatial dispersion when embedded in biological tissues. This study deals with the development of a multimodal contrast agent based on an injectable hydrogel nanocomposite containing a lanthanide-activated layered double hydroxide coupled to a biocompatible dye (indocyanine green), emitting in the first biological window. This novel nanostructured thermogelling hydrogel behaves as an efficient tissue marker for optical and magnetic resonance imaging because the particular formulation strongly limits its spatial diffusion in biological tissue by exploiting a simple injection. The synergistic combination of these properties permits to employ the hydrogel ink simultaneously for both optical and magnetic resonance imaging, easy monitoring of the biological target, and, at the same time, increasing the spatial resolution during a clinical surgery. The biocompatibility and excellent performance as contrast agents are very promising for possible use in image-guided surgery, which is currently one of the most challenging topics in clinical research.

Enhanced TfR1 Recognition of Myocardial Injury after Acute Myocardial Infarction with Cardiac Fibrosis via Pre-Degrading Excess Fibrotic Collagen.

The fibrosis process after myocardial infarction (MI) results in a decline in cardiac function due to fibrotic collagen deposition and contrast agents' metabolic disorders, posing a significant challenge to conventional imaging strategies in making heart damage clear in the fibrosis microenvironment. To address this issue, we developed an imaging strategy. Specifically, we pretreated myocardial fibrotic collagen with collagenase I combined with human serum albumin (HSA-C) and subsequently visualized the site of cardiac injury by near-infrared (NIR) fluorescence imaging using an optical contrast agent (CI, CRT-indocyanine green) targeting transferrin receptor 1 peptides (CRT). The key point of this strategy is that pretreatment with HSA-C can reduce background signal interference in the fibrotic tissue while enhancing CI uptake at the heart lesion site, making the boundary between the injured heart tissue and the normal myocardium clearer. Our results showed that compared to that in the untargeted group, the normalized fluorescence intensity of cardiac damage detected by NIR in the targeted group increased 1.28-fold. The normalized fluorescence intensity increased 1.21-fold in the pretreatment group of the targeted groups. These data demonstrate the feasibility of applying pretreated fibrotic collagen and NIR contrast agents targeting TfR1 to identify ferroptosis at sites of cardiac injury, and its clinical value in the management of patients with MI needs further study.

One-step synthesis of highly fluorescent perovskite nanocrystals in antisolvent for bioimaging

All inorganic perovskite nanocrystals (CsPbX3 NCs) have excellent optical properties with high quantum yield, size tunable absorption and emission spectra which makes them popular for a wide variety of applications. All the commonly used synthesis techniques, such as hot injection and ligand assisted reprecipitation method (LARP), use ‘good’ solvent such as dimethyl formamide, dimethyl sulfoxide or octadecene to dissolve the precursor salts. The CsPbX3 NCs formation is triggered either by rapid injection of the dissolved precursor salt in hot mixture (hot injection) or by adding a ‘good’ solvent into a ‘poor’ solvent (LARP) that induces crystallization. Here, we present an alternative synthesis of CsPbX3 perovskite nanocrystals in an antisolvent system, instead of a ‘good’ solvent. Crystallization in the antisolvent is induced by adding a trace amount of water, leading to the formation of highly bright CsPbX3 nanocrystals. This method resulted in a maximum photoluminescent quantum yield of ∼91%. Furthermore, these CsPbBr3 NCs can be modified to create core–shell structures with polymers such as silica, in the same pot. Encapsulating the NCs within a protective silica shell resulted in vastly superior water stability compared to the bare NCs. The silica coated CsPbBr3 NCs showed strong fluorescence in water were used to label breast cancer cells, thereby demonstrating its potential as an optical contrast agent for advanced bioimaging applications. Overall, this synthesis approach requires minimal steps and time, and can be carried out in an ambient atmosphere, thereby increasing its versatility and practicality, which is particularly attractive in low-resource settings.

Biomimetic bright optotheranostics for metastasis monitoring and multimodal image-guided breast cancer therapeutics

Nanoparticle formulations blending optical imaging contrast agents and therapeutics have been a cornerstone of preclinical theranostic applications. However, nanoparticle-based theranostics clinical translation faces challenges on reproducibility, brightness, photostability, biocompatibility, and selective tumor targeting and penetration. In this study, we integrate multimodal imaging and therapeutics within cancer cell-derived nanovesicles, leading to biomimetic bright optotheranostics for monitoring cancer metastasis. Upon NIR light irradiation, the engineered optotheranostics enables deep visualization and precise localization of metastatic lung, liver, and solid breast tumors along with solid tumor ablation. Metastatic cell-derived nanovesicles (∼80 ± 5 nm) are engineered to encapsulate imaging (emissive organic dye and gold nanoparticles) and therapeutic agents (anticancer drug doxorubicin and photothermally active organic indocyanine green dye). Systemic administration of biomimetic bright optotheranostic nanoparticles shows escape from mononuclear phagocytic clearance with (i) rapid tumor accumulation (3 h) and retention (up to 168 h), (ii) real-time monitoring of metastatic lung, liver, and solid breast tumors and (iii) 3-fold image-guided solid tumor reduction. These findings are supported by an improvement of X-ray, fluorescence, and photoacoustic signals while demonstrating a tumor reduction (201 mm3) in comparison with single therapies that includes chemotherapy (134 mm3), photodynamic therapy (72 mm3), and photothermal therapy (88mm3). The proposed innovative platform opens new avenues to improve cancer diagnosis and treatment outcomes by allowing the monitorization of cancer metastasis, allowing the precise cancer imaging, and delivering synergistic therapeutic agents at the solid tumor site.

3D imaging of aqueous veins and surrounding sclera using a dual-wavelength photoacoustic microscopy.

Understanding aqueous outflow resistance at the level of aqueous veins has been a challenge to the management of glaucoma. This study investigated resolving the anatomies of aqueous veins and the textures of surrounding sclera using photoacoustic microscopy (PAM). A dual wavelength PAM system was established and validated using imaging phantoms, porcine and human globes perfused with an optical contrast agent ex vivo. The system shows lateral resolution of 8.23 µm and 4.70 µm at 1200 nm and 532 nm, respectively, and an axial resolution of 27.6 µm. The system is able to separately distinguish the aqueous veins and the sclera with high contrast in full circumference of the porcine and human globes.

Molecular Imaging of ACE2 Expression in Infectious Disease and Cancer.

Angiotensin-converting enzyme 2 (ACE2) is a cell-surface receptor that plays a critical role in the pathogenesis of SARS-CoV-2 infection. Through the use of ligands engineered for the receptor, ACE2 imaging has emerged as a valuable tool for preclinical and clinical research. These can be used to visualize the expression and distribution of ACE2 in tissues and cells. A variety of techniques including optical, magnetic resonance, and nuclear medicine contrast agents have been developed and employed in the preclinical setting. Positron-emitting radiotracers for highly sensitive and quantitative tomography have also been translated in the context of SARS-CoV-2-infected and control patients. Together this information can be used to better understand the mechanisms of SARS-CoV-2 infection, the potential roles of ACE2 in homeostasis and disease, and to identify potential therapeutic modulators in infectious disease and cancer. This review summarizes the tools and techniques to detect and delineate ACE2 in this rapidly expanding field.

A pH-Activatable Nanoprobe Labels Diverse Histologic Subtypes of Human Lung Cancer During Resection.

Intraoperative molecular imaging (IMI) uses tumor-targeted optical contrast agents to improve identification and clearance of cancer during surgery. Recently, pH-activatable contrast agents have been developed but none has been tested in lung cancer. Here, we report the successful clinical translation of pegsitacianine (ONM-100), a pH-activatable nanoprobe, for fluorescence-guided lung cancer resection. We first characterized the pH setpoint for pegsitacianine fluorescence activation in vitro. We then optimized the specificity, dosing, and timing of pegsitacianine in murine flank xenograft models of lung adenocarcinoma and squamous cell carcinoma. Finally, we tested pegsitacianine in humans undergoing lung cancer surgery as part of an ongoing phase 2 trial. We found that the fluorescence activation of pegsitacianine occurred below physiologic pH in vitro. Using preclinical models of lung cancer, we found that the probe selectively labeled both adenocarcinoma and squamous cell carcinoma xenografts (mean tumor-to-background ratio [TBR] > 2.0 for all cell lines). In the human pilot study, we report cases in which pegsitacianine localized pulmonary adenocarcinoma and pulmonary squamous cell carcinoma (TBRs= 2.7 and 2.4) in real time to illustrate its successful clinical translation and potential to improve surgical management. This translational study demonstrates the feasibility of pegsitacianine as an IMI probe to label the two most common histologic subtypes of human lung cancer.

Exploring the Effect of Size Variability on Efficiency of Upconversion Nanoparticles as Optical Contrast Agents.

The current works explores the optical contrast property and nanaotheranostic capabilities of the rare earth based Upconversion nanoparticles. Optical coherence tomography (OCT) has been used to explore the particles ability to increase contrast and improve signal intensity. Photo thermal OCT, a function extension of OCT has been used to gauge the photo thermal potential of the nanoparticles. The nanoparticles successfully improved contrast and information from the deeper layers of the sample. The particles also showed excellent capability for use as photo thermal agents.

Intervalence charge transfer of Cr3+-Cr3+ aggregation for NIR-II luminescence

The increasing demand for high-contrast biological imaging, non-destructive testing, and infrared night vision can be addressed by the development of high-performance NIR light-emitting materials. Unlike lanthanide (Ln3+) with sharp-line multiplets and isolated Cr3+ with NIR-I emission, this study reports the first-ever NIR-II broadband luminescence based on the intervalence charge transfer (IVCT) of Cr3+-Cr3+ aggregation in gallate magentoplumbite. In particular, LaMgGa11O19:0.7Cr3+ exhibits dual-emission (NIR-I, 890 nm and NIR-II, 1200 nm) with a full width at half maximum (FWHM) of 626 nm under 450 nm blue LED excitation. Moreover, this dual-emission exhibits anti-thermal quenching behavior (432% @ 290 K), attributed to the energy transfer among multiple Cr3+ centers. Cryogen absorption spectra, lifetimes decay (2.3 ms), and electron paramagnetic experiments reveal the NIR-II luminescence of the Cr3+-Cr3+ → Cr2+-Cr4+ IVCT transition. The application of LaMgGa11O19:0.7Cr3+ in NIR-II biological imaging as an optical contrast agent, non-destructive testing, and night vision is demonstrated. This work provides new insights into broadband NIR-II luminescence under UV-NIR excitation based on the IVCT of Cr3+-Cr3+ aggregation.

Intraoperative molecular imaging: 3rd biennial clinical trials update.

This third biennial intraoperative molecular imaging (IMI) conference shows how optical contrast agents have been applied to develop clinically significant endpoints that improve precision cancer surgery. National and international experts on IMI presented ongoing clinical trials in cancer surgery and preclinical work. Previously known dyes (with broader applications), new dyes, novel nonfluorescence-based imaging techniques, pediatric dyes, and normal tissue dyes were discussed. Principal investigators presenting at the Perelman School of Medicine Abramson Cancer Center's third clinical trials update on IMI were selected to discuss their clinical trials and endpoints. Dyes that are FDA-approved or currently under clinical investigation in phase 1, 2, and 3 trials were discussed. Sections on how to move benchwork research to the bedside were also included. There was also a dedicated section for pediatric dyes and nonfluorescence-based dyes that have been newly developed. IMI is a valuable adjunct in precision cancer surgery and has broad applications in multiple subspecialties. It has been reliably used to alter the surgical course of patients and in clinical decision making. There remain gaps in the utilization of IMI in certain subspecialties and potential for developing newer and improved dyes and imaging techniques.

On the potential application of surface plasmon-based core-shell particles to study blood functional parameters

We investigated the application of gold nanoshell particles as optical sensors and contrast agents to study the blood functional parameters. Gold nanoshell particles with a core size of 1 μm that exhibit two prominent plasmonic peaks at 750 and 830 nm were developed. The peaks correspond to the wavelengths typically used to study the oxygen saturation of the blood. The plasmonic properties of gold nanoshells in media with various refractive indices were studied. Glucose samples with concentrations 0, 15, and 20%w/v in water were used. The 750 and 830 nm plasmonic peaks exhibit peak wavelength shifts of 63.77 ± 49.40 nm and 31.18 ± 20.94 nm per unit refractive index change. The optical properties of blood samples mixed with gold nanoshells were also measured. The optical absorption of blood samples increased by 7% at these wavelengths in the presence of the nanoshells. The plasmonic peaks at 750 and 830 nm showed a 3.57 ± 0.56 and 1.44 ± 0.55 percentage variation in absorbance for a 1% change in hematocrit. The enhanced optical absorption at these wavelengths suggests that these particles are effective optical sensors/contrast agents for multimodal optical and photoacoustic sensing and imaging.

Photoacoustic imaging for characterization of radiofrequency ablated cardiac tissues.

Photoacoustic (PA) imaging is an emerging technique being explored for various clinical applications. PA imaging offers a portable, inexpensive, stand-alone modality for evaluating optical contrast agents. PA signals are well-correlated with tissue physical parameters and can quantify various physiological variables (e.g., oxygenation of hemoglobin). Moreover, radiofrequency (RF) ablation is a promising treatment for certain cardiac arrhythmias. Assessment of RF-ablated lesions is of clinical importance. The purpose of this study is to elaborate the PA imaging to characterize RF-ablated cardiac tissues. Specifically, we describe the application of PA imaging to identify, characterize, and quantify cardiac RF lesions, highlighting the fundamental principles and unique benefits of this optical imaging technique. Potential future clinical application of PA imaging that reveals additional information about structural damage in RF-treated cardiac tissue are also anticipated.

Single-institution experience of 500 pulmonary resections guided by intraoperative molecular imaging

ObjectiveIntraoperative molecular imaging (IMI) using tumor-targeted optical contrast agents can improve thoracic cancer resections. There are no large-scale studies to guide surgeons in patient selection or imaging agent choice. Here, we report our institutional experience with IMI for lung and pleural tumor resection in 500 patients over a decade. MethodsBetween December 2011 and November 2021, patients with lung or pleural nodules undergoing resection were preoperatively infused with 1 of 4 optical contrast tracers: EC17, TumorGlow, pafolacianine, or SGM-101. Then, during resection, IMI was used to identify pulmonary nodules, confirm margins, and identify synchronous lesions. We retrospectively reviewed patient demographic data, lesion diagnoses, and IMI tumor-to-background ratios (TBRs). ResultsFive hundred patients underwent resection of 677 lesions. We found that there were 4 types of clinical utility of IMI: detection of positive margins (n = 32, 6.4% of patients), identification of residual disease after resection (n = 37, 7.4%), detection of synchronous cancers not predicted on preoperative imaging (n = 26, 5.2%), and minimally invasive localization of nonpalpable lesions (n = 101 lesions, 14.9%). Pafolacianine was most effective for adenocarcinoma-spectrum malignancies (mean TBR, 2.84), and TumorGlow was most effective for metastatic disease and mesothelioma (TBR, 3.1). False-negative fluorescence was primarily seen in mucinous adenocarcinomas (mean TBR, 1.8), heavy smokers (>30 pack years; TBR, 1.9), and tumors greater than 2.0 cm from the pleural surface (TBR, 1.3). ConclusionsIMI may be effective in improving resection of lung and pleural tumors. The choice of IMI tracer should vary by the surgical indication and the primary clinical challenge.

Preclinical Identification Of Tumor-Draining Lymph Nodes Using a Multimodal Non-invasive In vivo Imaging Approach

PurposeResection of the tumor-draining lymph -node (TDLN) represents a standard method to identify metastasis for several malignancies. Interestingly, recent preclinical studies indicate that TDLN resection diminishes the efficacy of immune checkpoint inhibitor-based cancer immunotherapies. Thus, accurate preclinical identification of TDLNs is pivotal to uncovering the underlying immunological mechanisms. Therefore, we validated preclinically, and clinically available non-invasive in vivo imaging approaches for precise TDLN identification.ProceduresFor visualization of the lymphatic drainage into the TDLNs by non-invasive in vivo optical imaging, we injected the optical imaging contrast agents Patent Blue V (582.7 g mol−1) and IRDye® 800CW polyethylene glycol (PEG; 25,000–60,000 g mol−1), subcutaneously (s.c.) in close proximity to MC38 adenocarcinomas at the right flank of experimental mice. For determination of the lymphatic drainage and the glucose metabolism in TDLNs by non-invasive in vivo PET/magnetic resonance imaging (PET/MRI), we injected the positron emission tomography (PET) tracer (2-deoxy-2[18F]fluoro-D-glucose (18F-FDG) [181.1 g mol−1]) in a similar manner. For ex vivo cross-correlation, we isolated TDLNs and contralateral nontumor-draining lymph nodes (NTDLNs) and performed optical imaging, biodistribution, and autoradiography analysis.ResultsThe clinically well-established Patent Blue V was superior for intraoperative macroscopic identification of the TDLNs compared with IRDye® 800CW PEG but was not sensitive enough for non-invasive in vivo detection by optical imaging. Ex vivo Patent Blue V biodistribution analysis clearly identified the right accessory axillary and the proper axillary lymph node (LN) as TDLNs, whereas ex vivo IRDye® 800CW PEG completely failed. In contrast, functional non-invasive in vivo18F-FDG PET/MRI identified a significantly elevated uptake exclusively within the ipsilateral accessory axillary TDLN of experimental mice and was able to differentiate between the accessory axillary and the proper LN. Ex vivo biodistribution and autoradiography confirmed our in vivo18F-FDG PET/MRI results.ConclusionsWhen taken together, our results demonstrate the feasibility of 18F-FDG-PET/MRI as a valid method for non-invasive in vivo, intraoperative, and ex vivo identification of the lymphatic drainage and glucose metabolism within the TDLNs. In addition, using Patent Blue V provides additive value for the macroscopic localization of the lymphatic drainage both visually and by ex vivo optical imaging analysis. Thus, both methods are valuable, easy to implement, and cost-effective for preclinical identification of the TDLN.

A study on modeling of rat tumors with the discrete-time Gompertz model

Cancer formation is one of the pathologies whose frequency has increased in the recent years. In the literature, the compartment models, which are non-linear, are used for such problems. In nonlinear compartment models, nonlinear state space models and the extended Kalman filter (EKF) are used to estimate the parameter and the state vector. This paper presents a discrete-time Gompertz model (DTGM) for the transfer of optical contrast agent, namely indocyanine green (ICG), in the presence of tumors between the plasma and extracellular extravascular space (EES) compartments. The DTGM, which is proposed for ICG and the estimation of ICG densities used in the vascular invasion of tumor cells of the compartments and in the measurement of migration from the intravascular area to the tissues, is obtained from the experimental data of the study. The ICG values are estimated online (recursive) using the DTGM and the adaptive Kalman filter (AKF) based on the experimental data. By employing the data, the results show that the DTGM in conjunction with the AKF provides a good analysis tool for modeling the ICG in terms of mean square error (MSE), mean absolute percentage error (MAPE), and . When the results obtained from the compartment model used in the reference [9] are compared with the results obtained with the DTGM, the DTGM gives better results in terms of MSE, MAPE and $R^2$ criteria. The DTGM and the AKF compartment model require less numerical processing when compared to the EKF, which indicates that DTGM is a less complicated model. In the literature, EKF is used for such problems.

Presence of non-Newtonian fluid in invasive pulmonary mucinous adenocarcinomas impacts fluorescence during intraoperative molecular imaging of lung cancer.

Intraoperative molecular imaging (IMI) with folate-targeted NIR tracers has been shown to improve lesion localization in more than 80% of lung adenocarcinomas. However, mucinous adenocarcinomas (MAs) and invasive mucinous adenocarcinomas (IMAs) of the lung, which are variants of adenocarcinoma, appear to have decreased fluorescence despite appropriate folate receptor expression on the tumor surface. We hypothesized that the etiology may be related to light excitation and emission through non-Newtonian fluid (mucin) produced by goblet and columnar cancer cells. Intraoperative data for 311 subjects were retrospectively reviewed from a prospectively collected 6-year database. For standardization, all patients underwent infusion of the same targeted molecular optical contrast agent (pafolacianine, folate receptor-targeted NIR fluorochrome) for lung cancer resections. Then, the ratio of the mean fluorescence intensity of the tumors and background tissues (TBR) was calculated. Tumors were examined for mucin, FRa, FRb, and immunofluorescent tracer uptake by a board-certified pathologist. The optical properties of mucin analyzed by imaging software were used to create in vitro gel models to explore the effects on NIR tracer fluorescence intensity. A large proportion (192, 62%) of the patients were female, with an average of 62.8years and a 34-year mean pack smoking history. There were no severe (Clavien-Dindo &gt; III) complications related to pafolacianine infusion. A total of 195 lesions in the study were adenocarcinomas, of which 19 (6.1%) were of the mucinous subtype. A total of 14/19 of the patients had a smoking history, and more than 74% of the IMA lesions were in the lower lobes. IMA lesions had a lower in situ TBR than nonmucinous adenocarcinomas (2.64 SD 0.23) vs (3.45 SD 0.11), respectively (p &lt; 0.05). Only 9/19 (47%) were localized in situ. Tumor bisection and removal of mucin from IMAs significantly increased pafolacianine fluorescence, with resultant TBR not being significantly different from the control group (4.67 vs 4.89) (p = 0.19). Of the 16 lesions that underwent FR expression analysis, 15/16 had FR presence on cancer cells or tumor-associated macrophages in the tumor microenvironment. There was no statistically significant difference in fluorescence intensity during immunofluorescence analysis (4.99 vs 5.08) (p = 0.16). Physical removal of mucin from IMAs improved the TBR from 3.11 to 4.67 (p &lt; 0.05). In vitro analysis of the impact of synthetic non-Newtonian fluid (agarose 0.5%) on NIR tracer fluorescence showed a decrease in MFI by a factor of 0.25 regardless of the concentration for each 5mm thickness of mucin. The mucinous subtype of lung adenocarcinomas presents a unique challenge in pafolacianine-targeted IMI-guided resections. The presence of non-Newtonian fluids presents a physical barrier that dampens the excitation of the tracer and fluorescence emission detected by the camera. Knowledge of this phenomenon can allow the surgeon to critically analyze lesion fluorescence parameters during IMI-guided lung cancer resections.

Comparative Experience of Short-wavelength Versus Long-wavelength Fluorophores for Intraoperative Molecular Imaging of Lung Cancer.

Intraoperative molecular imaging (IMI) using tumor-targeted optical contrast agents can improve cancer resections. The optimal wavelength of the IMI tracer fluorophore has never been studied in humans and has major implications for the field. To address this question, we investigated 2 spectroscopically distinct fluorophores conjugated to the same targeting ligand. Between December 2011 and November 2021, patients with primary lung cancer were preoperatively infused with 1 of 2 folate receptor-targeted contrast tracers: a short-wavelength folate-fluorescein (EC17; λ em =520nm) or a long-wavelength folate-S0456 (pafolacianine; λ em =793nm). During resection, IMI was utilized to identify pulmonary nodules and confirm margins. Demographic data, lesion diagnoses, and fluorescence data were collected prospectively. Two hundred eighty-two patients underwent resection of primary lung cancers with either folate-fluorescein (n=71, 25.2%) or pafolacianine (n=211, 74.8%). Most tumors (n=208, 73.8%) were invasive adenocarcinomas. We identified 2 clinical applications of IMI: localization of nonpalpable lesions (n=39 lesions, 13.8%) and detection of positive margins (n=11, 3.9%). In each application, the long-wavelength tracer was superior to the short-wavelength tracer regarding depth of penetration, signal-to-background ratio, and frequency of event. Pafolacianine was more effective for detecting subpleural lesions (mean signal-to-background ratio=2.71 vs 1.73 for folate-fluorescein, P <0.0001). Limit of signal detection was 1.8cm from the pleural surface for pafolacianine and 0.3cm for folate-fluorescein. Long-wavelength near-infrared fluorophores are superior to short-wavelength IMI fluorophores in human tissues. Therefore, future efforts in all human cancers should likely focus on long-wavelength agents.

(Invited) Rare-Earth-Based Nanoparticles As Multimodal Bioprobes

The remarkable optomagnetic properties of the rare-earths (RE) make RE-based materials ideal for biomedical applications, including diagnostic (e.g., imaging, nanothermometry) and therapeutic (e.g., drug delivery, photodynamic therapy) approaches. This is due the unique electronic properties of the f-elements allowing for upconversion and near-infrared emission under near-infrared excitation as well as high magnetic moments.Yet, challenges remain; low emission intensity and efficiency of small nanoparticles (NPs), and reliable, fast synthesis routes. As material chemists, we tackle these challenges with new designs of RE-NPs by chemically controlled synthesis, application-oriented surface chemistry, and understanding of structure-property-relationships. Sodium rare-earth fluorides (NaREF4) are our favorite materials, and we developed a fast and reliable microwave-assisted synthesis approach allowing crystalline phase and size control in the sub 15nm realm. Such control is crucial for the understanding of fundamental structure-property relationships and to optimize their optical and magnetic properties, when aiming for the design of next-generation optical probes or contrast agents for magnetic resonance imaging. For instance, NaGdF4 NPs are gaining interest as alternative MRI contrast agent, while co-doping with RE3+ ions renders them excellent candidates for photoluminescent optical probes. The hexagonal crystalline phase of NaGdF4 is known as the more efficient host material for upconversion emission, yet interestingly, it was found that its cubic counterpart shows superior performance as MRI contrast agent. Having a fast and reliable synthesis route towards NaREF4 NPs on hand, we now explore various nanoparticle architectures and compositions with the goal to optimize their optomagnetic properties, ultimately resulting in the design of biocompatible multimodal bioprobes.This presentation will shed light on recent results and remaining challenges in the field of RE-based nanostructures with respect to their microwave-assisted synthesis as well as structural and optomagnetic properties, seeking biomedical application, while also touching on hyperspectral imaging as an emerging analytical tool offering spatio-spectral information about RE-based materials.