Sonophore-enhanced nanoemulsions for optoacoustic imaging of cancer

Nanoemulsions: Summary of a Decade of Research and Recent Advances

Nanoemulsions consist of a combination of several components such as oil, water, emulsifiers, surfactants and cosurfactants. Various techniques for producing nanoemulsions include high-energy and low-energy approaches such as high-pressure homogenization, microfluidization, jet disperser and phase inversion methods. The properties of a formulation can be influenced by elements such as the composition, concentration, size and charge of droplets, which in turn can affect the technique of manufacture. Characterization is conducted by the assessment of several factors such as physical properties, pH analysis, viscosity measurement and refractive index determination. This article offers a thorough examination of the latest developments in nanoemulsion technology, with a focus on their wide-ranging applications and promising future possibilities. It also discusses the administration of nanoemulsions through several methods.

"Plasmonic Nanomaterials": An emerging avenue in biomedical and biomedical engineering opportunities

BACKGROUND

Plasmonic nanomaterials asnoble metal-based materials have unique optical characteristic upon exposure to incident light with an appropriate wavelength. Today, generated plasmon by nanoparticles has receivedincreasingattention in nanomedicine; from diagnosis, tissue and tumor imaging to therapeutic and biomedical engineering.

AIM OF REVIEW

Due to rapid growing of knowledge in the inorganic nanomaterial field, this paper aims to be a comprehensive and authoritative, critical, and broad interest to the scientific community. Here, we introduce basic physicochemical properties of plasmonic nanoparticles and their applications in biomedical and tissue engineering The first part of each division explain the basic physico-chemical properties of each nanomaterial with a graphical abstract. In the second part, concepts by describing classic examples taken from the biomedical and biomedical engineering literature are illustrated. The selected case studies are intended to give an overview of the different systems and mechanisms utilized in nanomedicine.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this communication, we have tried to introduce the needed concepts of plasmonic nanomaterials and their implication in a particular part of biomedical over the last 20 years. Moreover, in each part with insist on limitations, a perspective is presented which can guide a researcher how they can develop or modify new scaffolds for biomedical engineering.

Multiplexed imaging in oncology

In oncology, technologies for clinical molecular imaging are used to diagnose patients, establish the efficacy of treatments and monitor the recurrence of disease. Multiplexed methods increase the number of disease-specific biomarkers that can be detected simultaneously, such as the overexpression of oncogenic proteins, aberrant metabolite uptake and anomalous blood perfusion. The quantitative localization of each biomarker could considerably increase the specificity and the accuracy of technologies for clinical molecular imaging to facilitate granular diagnoses, patient stratification and earlier assessments of the responses to administered therapeutics. In this Review, we discuss established techniques for multiplexed imaging and the most promising emerging multiplexing technologies applied to the imaging of isolated tissues and cells and to non-invasive whole-body imaging. We also highlight advances in radiology that have been made possible by multiplexed imaging.

Beta-adrenergic glaucoma drugs reduce lymphatic clearance from the eye: A sequential photoacoustic imaging study

Our study aims to determine whether the beta-adrenergic system is involved in the regulation of lymphatic drainage from the eye. For this purpose, we assessed the effect of 2 topical beta-adrenergic blockers, timolol and betaxolol, commonly used as glaucoma drugs, on lymphatic clearance of albumin from the aqueous humor to neck lymph nodes. Adult mice were treated with either topical timolol, a non-selective β-blocker, 0.5% (n = 8), or topical betaxolol, a selective β₁-adrenergic blocker, 0.5% (n = 6) twice daily for 14 days and compared to respective control groups (n = 5 and n = 7). Changes in lymphatic clearance from the eye were assessed using a quantitative in vivo photoacoustic imaging approach. In all subjects, right eye and neck lymph nodes were longitudinally assessed by sequential photoacoustic imaging just prior to near-infrared dye injection into the anterior chamber of the eye, and 20 min, 2 and 4 h after injection. Repeat measurements of mean pixel intensities (MPIs) of right eyes and nodes were performed at all timepoints. The areas under the curves (AUC) were calculated and the AUC of the treated-group was compared to that of controls using the Mann-Whitney U test. The slopes of MPI of each region of interest over time were compared using the linear mixed model after adjusting for IOP decrease after treatment and other parameters such as sex and body weight. In the timolol-treated group, right neck nodes showed significant decrease in AUC signal intensity compared with controls (P = 0.003), and significant decrease in slope of MPI compared with controls (P = 0.0025). In the betaxolol-treated group, right neck nodes showed significant decrease in AUC signal intensity compared with controls (P = 0.02), and significant decrease in slope of MPI compared with controls (P = 0.0069). Topical treatment with timolol and betaxolol reduced lymphatic clearance of albumin from the aqueous humor to the neck lymph nodes. This finding may be relevant for the management of secondary glaucomas and inflammatory eye disease in which the clearance of accumulated proteins and antigen from the eye is important to disease recovery and sight protection. This study suggests that the beta-adrenergic system plays a role in the regulation of lymphatic clearance from the eye.

Emerging contrast agents for multispectral optoacoustic imaging and their biomedical applications

Optoacoustic imaging is a hybrid biomedical imaging modality which collects ultrasound waves generated via photoexciting contrast agents in tissues and produces images of high resolution and penetration depth. As a functional optoacoustic imaging technique, multispectral optoacoustic imaging, which can discriminate optoacoustic signals from different contrast agents by illuminating samples with multi-wavelength lasers and then processing the collected data with specific algorithms, assists in the identification of a specific contrast agent in target tissues and enables simultaneous molecular and physiological imaging. Moreover, multispectral optoacoustic imaging can also generate three-dimensional images for biological tissues/samples with high resolution and thus holds great potential in biomedical applications. Contrast agents play essential roles in optoacoustic imaging, and they have been widely explored and applied as probes and sensors in recent years, leading to the emergence of a variety of new contrast agents. In this review, we aim to summarize the latest advances in emerging contrast agents, especially the activatable ones which can respond to specific biological stimuli, as well as their preclinical and clinical applications. We highlight their design strategies, discuss the challenges and prospects in multispectral optoacoustic imaging, and outline the possibility of applying it in clinical translation and public health services using synthetic contrast agents.

Optoacoustic Imaging of Glucagon-like Peptide-1 Receptor with a Near-Infrared Exendin-4 Analog

Limitations in current imaging tools have long challenged the imaging of small pancreatic islets in animal models. Here, we report the first development and in vivo validation testing of a broad-spectrum and high-absorbance near-infrared optoacoustic contrast agent, E4x12-Cy7. Our near-infrared tracer is based on the amino acid sequence of exendin-4 and targets the glucagon-like peptide-1 receptor (GLP-1R). Cell assays confirmed that E4x12-Cy7 has a high-binding affinity (dissociation constant, Kd, 4.6 ± 0.8 nM). Using the multispectral optoacoustic tomography, we imaged E4x12-Cy7 and optoacoustically visualized β-cell insulinoma xenografts in vivo for the first time. In the future, similar optoacoustic tracers that are specific for β-cells and combines optoacoustic and fluorescence imaging modalities could prove to be important tools for monitoring the pancreas for the progression of diabetes.

A novel photoacoustic-fluorescent contrast agent for quantitative imaging of lymphatic drainage

In vivo near-infrared (NIR) photoacoustic imaging (PAI) studies using novel contrast agents require validation, often via fluorescence imaging. Bioconjugation of NIR dyes to proteins is a versatile platform to obtain contrast agents for specific biomedical applications. Nonfluorescent NIR dyes with higher photostability present advantages for quantitative PAI, compared to most fluorescent NIR dyes. However, they don't provide a fluorescence signal required for fluorescence imaging. Here, we designed a hybrid PA-fluorescent contrast agent by conjugating albumin with a NIR nonfluorescent dye (QC-1) and a visible spectrum fluorescent dye, a BODIPY derivative. The new hybrid tracer QC-1/BSA/BODIPY (QBB) had a low minimum detectable concentration (2.5μM), a steep linear range (2.4-54.4 μM; slope 3.39 E -5), and high photostability. Tracer signal was measured in vivo using PAI to quantify its drainage from eye to the neck and its localization in the neck lymph node was validated with postmortem fluorescence imaging.

Optical Imaging Modalities: Principles and Applications in Preclinical Research and Clinical Settings

With the ability to noninvasively image and monitor molecular processes within tumors, molecular imaging represents a fundamental tool for cancer scientists. In the current review, we describe emergent optical technologies for molecular imaging. We aim to provide the reader with an overview of the fundamental principles on which each imaging strategy is based, to introduce established and future applications, and to provide a rationale for selecting optical technologies for molecular imaging depending on disease location, biology, and anatomy. To accelerate clinical translation of imaging techniques, we also describe examples of practical applications in patients. Elevating these techniques into standard-of-care tools will transform patient stratification, disease monitoring, and response evaluation.

Photoacoustic Imaging Probes Based on Tetrapyrroles and Related Compounds

Photoacoustic imaging (PAI) is a rapidly evolving field in molecular imaging that enables imaging in the depths of ultrasound and with the sensitivity of optical modalities. PAI bases on the photoexcitation of a chromophore, which converts the absorbed light into thermal energy, causing an acoustic pressure wave that can be captured with ultrasound transducers, in generating an image. For in vivo imaging, chromophores strongly absorbing in the near-infrared range (NIR; > 680 nm) are required. As tetrapyrroles have a long history in biomedical applications, novel tetrapyrroles and inspired mimics have been pursued as potentially suitable contrast agents for PAI. The goal of this review is to summarize the current state of the art in PAI applications using tetrapyrroles and related macrocycles inspired by it, highlighting those compounds exhibiting strong NIR-absorption. Furthermore, we discuss the current developments of other absorbers for in vivo photoacoustic (PA) applications.

Theranostic application of nanoemulsions in chemotherapy

Theranostics has the potential to revolutionize the diagnosis, treatment, and prognosis of cancer, where novel drug delivery systems could be used to detect the disease at an early stage with instantaneous treatment. Various preclinical approaches of nanoemulsions with entrapped contrast and chemotherapeutic agents have been documented to act specifically on the tumor microenvironment (TME) for both diagnostic and therapeutic purposes. However, bringing these theranostic nanoemulsions through preclinical trials to patients requires several fundamental hurdles to be overcome, including the in vivo behavior of the delivery tool, degradation, and clearance from the system, as well as long-term toxicities. Here, we discuss recent advances in the application of nanoemulsions in molecular imaging with simultaneous therapeutic efficacy in a single delivery system.

Advances in optical and electrochemical techniques for biomedical imaging

Yi-Tao Long and Thomas J. Meade introduce the Chemical Science retrospective themed collection on advances in optical and electrochemical techniques for biomedical imaging.

Photoacoustic imaging of living mice enhanced with a low-cost contrast agent

One of the advantages of photoacoustic imaging (PAI) is that its image contrast may come from exogenous agents. Such advantage leads to the development of a great number of exogenous probes. However, the biosafety of most of these contrast agents has not yet been confirmed, thus hindering their clinical translation. In this work, we report on the utilization of a clinically commonly used nutritional medicine, the Intralipid, as a new contrast agent for photoacoustic imaging. Intralipid consists of soybean oil, lecithin and glycerin and has long been adapted in clinical practices, mainly as a parenteral nutrition. In our study, we found that with Intralipid, the imaging sensitivity of PAI can be effectively enhanced, as demonstrated in in vivo imaging of different organs of nude mice. Further imaging studies on cancerous mice showed not only a twofold PA signal enhancement, but also a strong and long-lasting signal aggregation in the tumor region. Our result revealed the potential of Intralipid to be used in clinical PAI applications, since it is clinically safe, and can be easily prepared at very low cost.

An Activatable Near-Infrared Chromophore for Multispectral Optoacoustic Imaging of Tumor Hypoxia and for Tumor Inhibition

Hypoxia is a key hallmark of solid tumors and tumor hypoxia usually contributes to cancer progression, therapeutic resistance and poor outcome. Accurately detecting and imaging tumor hypoxia with high spatial resolution would be conducive to formulating optimized treatment plan and thus achieving better patient outcome. Methods: Tumor hypoxia can cleave the azo linker and release a NIR fluorophore (NR-NH2) and release the active drug as well. NR-NH2 shows a strong absorption band at around 680 nm and a strong fluorescence band at 710 nm, allowing for both multispectral optoacoustic tomography imaging (MSOT) and fluorescent imaging of tumor hypoxia in a tumor-bearing mouse model. Results: Liposome encapsulated with the activatable chromophore (NR-azo) for detecting/imaging tumor hypoxia and for tumor inhibition was demonstrated. For this chromophore, a xanthene-based NIR fluorophore acts as the optoacoustic and fluorescent reporter, an azo linker serves as the hypoxia-responsive moiety and a nitrogen mustard as the therapeutic drug. NR-azo shows an absorption at around 575 nm but exhibits negligible fluorescence due to the existence of the strong electron-withdrawing azo linker. Conclusion: We demonstrated an optoacoustic and fluorescent system for not only imaging tumor hypoxia in vivo but also achieving tumor inhibition.

Acid specific dark quencher QC1 pHLIP for multi-spectral optoacoustic diagnoses of breast cancer

Breast cancer is the most common type of malignant growth in women. Early detection of breast cancer, as well as the identification of possible metastatic spread poses a significant challenge because of the structural and genetic heterogeneity that occurs during the progression of the disease. Currently, mammographies, biopsies and MRI scans are the standard of care techniques used for breast cancer diagnosis, all of which have their individual shortfalls, especially when it comes to discriminating tumors and benign growths. With this in mind, we have developed a non-invasive optoacoustic imaging strategy that targets the acidic environment of breast cancer. A pH low insertion peptide (pHLIP) was conjugated to the dark quencher QC1, yielding a non-fluorescent sonophore with high extinction coefficient in the near infrared that increases signal as a function of increasing amounts of membrane insertion. In an orthotopic murine breast cancer model, pHLIP-targeted optoacoustic imaging allowed us to differentiate between healthy and breast cancer tissues with high signal/noise ratios. In vivo, the sonophore QC1-pHLIP could detect malignancies at higher contrast than its fluorescent analog ICG-pHLIP, which was developed for fluorescence-guided surgical applications. PHLIP-type optoacoustic imaging agents in clinical settings are attractive due to their ability to target breast cancer and a wide variety of other malignant growths for diagnostic purposes. Intuitively, these agents could also be used for visualization during surgery.

Surface-enhanced Resonance Raman Scattering Nanoprobe Ratiometry for Detecting Microscopic Ovarian Cancer via Folate Receptor Targeting

Ovarian cancer represents the deadliest gynecologic malignancy. Most patients present at an advanced stage (FIGO stage III or IV), when local metastatic spread has already occurred. However, ovarian cancer has a unique pattern of metastatic spread, in that tumor implants are initially contained within the peritoneal cavity. This feature could enable, in principle, the complete resection of tumor implants with curative intent. Many of these metastatic lesions are microscopic, making them hard to identify and treat. Neutralizing such micrometastases is believed to be a major goal towards eliminating tumor recurrence and achieving long-term survival. Raman imaging with surface enhanced resonance Raman scattering nanoprobes can be used to delineate microscopic tumors with high sensitivity, due to their bright and bioorthogonal spectral signatures. Here, we describe the synthesis of two 'flavors' of such nanoprobes: an antibody-functionalized one that targets the folate receptor - overexpressed in many ovarian cancers - and a non-targeted control nanoprobe, with distinct spectra. The nanoprobes are co-administered intraperitoneally to mouse models of metastatic human ovarian adenocarcinoma. All animal studies were approved by the Institutional Animal Care and Use Committee of Memorial Sloan Kettering Cancer Center. The peritoneal cavity of the animals is surgically exposed, washed, and scanned with a Raman microphotospectrometer. Subsequently, the Raman signatures of the two nanoprobes are decoupled using a Classical Least Squares fitting algorithm, and their respective scores divided to provide a ratiometric signal of folate-targeted over untargeted probes. In this way, microscopic metastases are visualized with high specificity. The main benefit of this approach is that the local application into the peritoneal cavity - which can be done conveniently during the surgical procedure - can tag tumors without subjecting the patient to systemic nanoparticle exposure. False positive signals stemming from non-specific binding of the nanoprobes onto visceral surfaces can be eliminated by following a ratiometric approach where targeted and non-targeted nanoprobes with distinct Raman signatures are applied as a mixture. The procedure is currently still limited by the lack of a commercial wide-field Raman imaging camera system, which once available will allow for the application of this technique in the operating theater.

Ratiometric Photoacoustic Nanoprobe for Bioimaging of Cu2

Aberrant copper contents implicate numerous diseases including Alzheimer's disease and Wilson's disease. Conventional copper detection technologies are difficult to offer non-invasive and accurate deep tissue detection of copper. Here, we report a photoacoustic (PA) nanoprobe (NRh-IR-NMs) for ratiometric PA imaging of Cu²⁺. The nanoprobe consists of a selective Cu²⁺-responsive probe (NRh) as the indicator and a nonresponsive dye (IR) as the internal reference. In the presence of Cu²⁺, a selective Cu²⁺-induced structure change of NRh would take place, resulting in the increase of PA signal intensity increment at 716 nm (ΔPA716). However, the ΔPA834 which attributes to IR shows negligible change. Therefore, the ratiometric PA signal (ΔPA716/ΔPA834) could be used as an indicator for Cu²⁺ detection. This ratiometric PA detection method offers a noninvasive technology with high selectivity and tissue penetration depth, which is a promising tool for deep-tissue detection of Cu²⁺ in living organisms.

Nanoemulsion-Based Delivery of Fluorescent PARP Inhibitors in Mouse Models of Small Cell Lung Cancer

The preclinical potential of many diagnostic and therapeutic small molecules is limited by their rapid washout kinetics and consequently modest pharmacological performances. In several cases, these could be improved by loading the small molecules into nanoparticulates, improving blood half-life, in vivo uptake and overall pharmacodynamics. In this study, we report a nanoemulsion (NE) encapsulated form of PARPi-FL. As a proof of concept, we used PARPi-FL, which is a fluorescently labeled sensor for olaparib, a FDA-approved small molecule inhibitor of the nuclear enzyme poly(ADP-ribose)polymerase 1 (PARP1). Encapsulated PARPi-FL showed increased blood half-life, and delineated subcutaneous xenografts of small cell lung cancer (SCLC), a fast-progressing disease where efficient treatment options remain an unmet clinical need. Our study demonstrates an effective method for expanding the circulation time of a fluorescent PARP inhibitor, highlighting the pharmacokinetic benefits of nanoemulsions as nanocarriers and confirming the value of PARPi-FL as an imaging agent targeting PARP1 in small cell lung cancer.