In vivo imaging of tumors with protease-activated near-infrared fluorescent probes

A far-red to NIR emitting ultra-sensitive probe for the detection of endogenous HOCl in zebrafish and the RAW 264.7 cell line

We report the synthesis of a far-red to NIR emitting probe for its application to the endogenous fluorescence imaging of HOCl in zebrafish.

Bioresponse Inspired Nanomaterials for Targeted Drug and Gene Delivery

The traditional drug delivery techniques are unresponsive to the altering metabolic states of the body and fail to achieve target specific drug delivery, which results in toxic plasma concentrations. In order to harmonize the drug release profiles, diverse biological and pathological pathways and factors involved have been studied and consequently, nanomaterials and nanostructures are engineered in a manner so that they respond and interact with the target cells and tissues in a controlled manner to induce promising pharmacological responses with least undesirable effects. The bioinspired nanoparticles such as carbon nanotubes, metallic nanoparticles, and quantum dots sense the localized host environment for diagnosis and treatment of pathological states. These biocompatible polymeric- based nanostructures bind drugs to the specific receptors, which renders them as ideal vehicles for the delivery of drugs and gene. The ultimate goal of bioinspired nanocomposites is to achieve personalized diagnostic and therapeutic outcomes. This review briefly discussed current trends; role, recent advancements as well as different approaches, which are being used for designing and fabrication of some bioinspired nanocarriers.

Collagenase-Encapsulated pH-Responsive Nanoscale Coordination Polymers for Tumor Microenvironment Modulation and Enhanced Photodynamic Nanomedicine

The abundant tumor extracellular matrix (ECM) could result in insufficient tumor retention and ineffective intratumor penetration of therapeutic agents as well as an acidic and hypoxic tumor microenvironment (TME), leading to unsatisfactory therapeutic outcomes for many types of therapies. Therefore, developing strategies to modulate the TME by selectively degrading the condensed ECM may be helpful to improve existing cancer therapies. Herein, collagenase (CLG)-encapsulated nanoscale coordination polymers (NCPs) are synthesized based on Mn²⁺ and an acid-sensitive benzoic-imine organic linker and then modified by polyethylene glycol (PEG). Upon intravenous (iv) injection, these CLG@NCP-PEG nanoparticles show efficient accumulation within the tumor, in which CLG would be released because of the collapse of NCP structures within the acidic TME. The released CLG enzyme could then specifically degrade collagens, the major component of ECM, leading to a loosened ECM structure, enhanced tumor perfusion, and relieved hypoxia. As a result, the second wave of nanoparticles, chlorin e6 (Ce6)-loaded liposomes (liposome@Ce6), would exhibit enhanced retention and penetration within the tumor. Such phenomena together with relieved tumor hypoxia could then lead to greatly enhanced photodynamic therapeutic effect of liposome@Ce6 for mice pretreated with CLG@NCP-PEG. Our work thus presents a unique strategy for TME modulation using pH-responsive NCPs as smart enzyme carriers.

A 3E8.scFv.Cys-IR800 Conjugate Targeting TAG-72 in an Orthotopic Colorectal Cancer Model

PURPOSE

Optical surgical navigation (OSN) will be a potent tool to help surgeons more accurately and efficiently remove tumors. The purpose of this study was to evaluate a novel humanized 3E8 antibody (3E8 MAb) fragment site-specifically conjugated with IR800, 3E8.scFv.Cys-IR800, as a potential OSN agent to target colorectal adenocarcinoma.

PROCEDURES

An engineered single-chain variable fragment of 3E8 MAb (targeted to TAG-72), appending a C-terminal cysteine residue (3E8.scFv.Cys), was created and reacted with IRDye800-maleimide. 3E8.scFv.Cys-IR800 identity and purity were verified by MALDI-TOF mass spectra and 800 nm detected size exclusion column HPLC. In vitro human colon adenocarcinoma LS-174 T cells binding and competition assay validated biological functionality. We further evaluated the imaging ability and receptor-specific binding of 3E8.scFv.Cys-IR800 in an orthotopic LS-174 T mouse model.

RESULTS

A 1:1 dye to protein conjugate was achieved at greater than 90 % HPLC purity. A 1 nmol dose of 3E8.scFv.Cys-IR800 via intraperitoneal injection administration was sufficient to produce high tumor to background fluorescence contrast. Blocking competition studies both in vitro and in vivo using a different blocking protein, 3E8ΔCH2, demonstrated 3E8.scFv.Cys-IR800 binding specificity for TAG-72 antigen.

CONCLUSIONS

3E8.scFv.Cys-IR800 shows properties useful in a clinically viable OSN agent for colorectal cancer.

Doxorubicin-loaded protease-activated near-infrared fluorescent polymeric nanoparticles for imaging and therapy of cancer

INTRODUCTION

Despite significant progress in the field of oncology, cancer remains one of the leading causes of death. Chemotherapy is one of the most common treatment options for cancer patients but is well known to result in off-target toxicity. Theranostic nanomedicines that integrate diagnostic and therapeutic functions within an all-in-one platform can increase tumor selectivity for more effective chemotherapy and aid in diagnosis and monitoring of therapeutic responses.

MATERIAL AND METHODS

In this work, theranostic nanoparticles were synthesized with commonly used biocompatible and biodegradable polymers and used as cancer contrast and therapeutic agents for optical imaging and treatment of breast cancer. These core-shell nanoparticles were prepared by nanoprecipitation of blends of the biodegradable and biocompatible amphiphilic copolymers poly(lactic-co-glycolic acid)-b-poly-l-lysine and poly(lactic acid)-b-poly(ethylene glycol). Poly-l-lysine in the first copolymer was covalently decorated with near-infrared fluorescent Alexa Fluor 750 molecules.

RESULTS

The spherical nanoparticles had an average size of 60-80 nm. The chemotherapeutic drug doxorubicin was encapsulated in the core of nanoparticles at a loading of 3% (w:w) and controllably released over a period of 30 days. A 33-fold increase in near-infrared fluorescence, mediated by protease-mediated cleavage of the Alexa Fluor 750-labeled poly-l-lysine on the surface of the nanoparticles, was observed upon interaction with the model protease trypsin. The cytocompatibility of drug-free nanoparticles and growth inhibition of drug-loaded nanoparticles on MDA-MB-231 breast cancer cells were investigated with a luminescence cell-viability assay. Drug-free nanoparticles were found to cause minimal toxicity, even at high concentrations (0.2-2,000 µg/mL), while doxorubicin-loaded nanoparticles significantly reduced cell viability at drug concentrations >10 µM. Finally, the interaction of the nanoparticles with breast cancer cells was studied utilizing fluorescence microscopy, demonstrating the potential of the nanoparticles to act as near-infrared fluorescence optical imaging agents and drug-delivery carriers.

CONCLUSION

Doxorubicin-loaded, enzymatically activatable nanoparticles of less than 100 nm were prepared successfully by nanoprecipitation of copolymer blends. These nanoparticles were found to be suitable as controlled drug delivery systems and contrast agents for imaging of cancer cells.

Functional biomimetic nanoparticles for drug delivery and theranostic applications in cancer treatment

Nanotechnology has been extensively utilized in the design and development of powerful strategies for drug delivery and cancer theranostic. Nanoplatforms as a drug delivery system have many advantages such as in vivo imaging, combined drug delivery, extended circulation time, and systemic controlled release. The functional biomimetic drug delivery could be realized by incorporating stimuli-responsive (pH, temperature, redox potential, etc.) properties into the nanocarrier system, allowing them to bypass biological barriers and arrive at the targeted area. In this review, we discuss the role of internal stimuli-responsive nanocarrier system for imaging and drug delivery in cancer therapy. The development of internal stimuli-responsive nanoparticles is highlighted for precision drug delivery applications, with a particular focus on in vivo imaging, drug release performance, and therapeutic benefits.

A comparative profiling of oral cancer patients and high risk niswar users using FT-IR and chemometric analysis

Oral cancer is one of the major cancer types, which has increased sustainably in Southeast Asian countries due to the extensive use of a variety of tobacco and betel nut products. The current study is focused on developing an easy, efficient and cost-effective method for plasma profiling of oral cancer patients and tobacco users in order to have a progressive picture towards oral cancer. For this purpose, the profiling of 147 plasma samples including 67 oral cancer patients' samples, 60 "niswar" (a dipping tobacco product) user samples, and 20 healthy controls using attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), and chemometric analysis was carried out. Fingerprint region (500-1500 cm^-1) of all three groups showed interesting variations in peaks pattern. From these observations, height ratios of two bands H1646/H1550 and H1080/H1024 with p value of 2.01 × 10^-6 and 8.39 × 10^-7, respectively, showed a pattern between healthy to oral cancer and "niswar" user samples. Chemometric analysis of the data showed a clean separation among the groups. PLS-DA and OPLS-DA models provided 87.7% and 89.5% classification rate, respectively. Area under the curve (AUC) for healthy control, oral cancer and "niswar" users were found to be 0.97, 0.95 and 0.92%, respectively. The results of the present study indicate that FT-IR spectroscopy, in conjunction with chemometric data, can be effectively used for the preliminary differentiation of plasma samples of oral cancer patients, "niswar" users and control samples of healthy persons.

Carbonic Anhydrase IX-Targeted Near-Infrared Dye for Fluorescence Imaging of Hypoxic Tumors

Use of tumor-targeted fluorescence dyes to help surgeons identify otherwise undetected tumor nodules, decrease the incidence of cancer-positive margins, and facilitate localization of malignant lymph nodes has demonstrated considerable promise for improving cancer debulking surgery. Unfortunately, the repertoire of available tumor-targeted fluorescent dyes does not permit identification of all cancer types, raising the need to develop additional tumor-specific fluorescent dyes to ensure localization of all malignant lesions during cancer surgeries. By comparing the mRNA levels of the hypoxia-induced plasma membrane protein carbonic anhydrase IX (CA IX) in 13 major human cancers with the same mRNA levels in corresponding normal tissues, we document that CA IX constitutes a nearly universal marker for the design of tumor-targeted fluorescent dyes. Motivated by this expression profile, we synthesize two new CA IX-targeted near-infrared (NIR) fluorescent imaging agents and characterize their physical and biological properties both in vitro and in vivo. We report that conjugation of either acetazolamide or 6-aminosaccharin (i.e., two CA-IX-specific ligands) to the NIR fluorescent dye, S0456, via an extended phenolic spacer creates a brightly fluorescent dye that binds CA IX with high affinity and allows rapid visualization of hypoxic regions of solid tumors at depths >1 cm beneath a tissue surface. Taken together, these data suggest that a CA IX-targeted NIR dye can constitute a useful addition to a cocktail of tumor-targeted NIR dyes designed to image all human cancers.

Recent advancements in biocompatible inorganic nanoparticles towards biomedical applications

Due to their intrinsic physical properties potentially useful for imaging and therapy as well as their highly engineerable surface, biocompatible inorganic nanoparticles offer novel platforms to develop advanced diagnostic and therapeutic agents for improved detection and more efficacious treatment of major diseases. The in vivo application of inorganic nanoparticles was demonstrated more than two decades ago, however it turns out to be very complicated as nanomaterials exhibit much more sophisticated pharmacokinetic properties than conventional drugs. In this review, we first discuss the in vivo behavior of inorganic nanoparticles after systematic administration, including the basic requirements for nanoparticles to be used in vivo, the impact of the particles' physicochemical properties on their pharmacokinetics, and the effects of the protein corona formed across the nano-bio interface. Next, we summarize the state-of-the-art of the preparation of biocompatible inorganic nanoparticles and bioconjugation strategies for obtaining target-specific nanoprobes. Then, the advancements in sensitive tumor imaging towards diagnosis and visualization of the abnormal signatures in the tumor microenvironment, together with recent studies on atherosclerosis imaging are highlighted. Finally, the future challenges and the potential for inorganic nanoparticles to be translated into clinical applications are discussed.

Targeted Optical Imaging Agents in Cancer: Focus on Clinical Applications

Molecular imaging is an emerging strategy for in vivo visualization of cancer over time based on biological mechanisms of disease activity. Optical imaging methods offer a number of advantages for real-time cancer detection, particularly in the epithelium of hollow organs and ducts, by using a broad spectral range of light that spans from visible to near-infrared. Targeted ligands are being developed for improved molecular specificity. These platforms include small molecule, peptide, affibody, activatable probes, lectin, and antibody. Fluorescence labeling is used to provide high image contrast. This emerging methodology is clinically useful for early cancer detection by identifying and localizing suspicious lesions that may not otherwise be seen and serves as a guide for tissue biopsy and surgical resection. Visualizing molecular expression patterns may also be useful to determine the best choice of therapy and to monitor efficacy. A number of these imaging agents are overcoming key challenges for clinical translation and are being validated in vivo for a wide range of human cancers.

Dramatic Enhancement of Quantum Cutting in Lanthanide-Doped Nanocrystals Photosensitized with an Aggregation-Induced Enhanced Emission Dye

Applications of multiphoton processes in lanthanide-doped nanophosphors (NPs) are often limited by relatively weak and narrow absorbance. Here, the concept of an ultimate photosensitization by aggregation-induced enhanced emission (AIEE) dyes to overcome this limitation is introduced. Because AIEE dyes do not suffer from concentration quenching, they can fully cover the NP surface at high density to maximize absorbance while passivating the surface. This concept is applied to multiphoton down-conversion by quantum cutting. Specifically, coating Yb³⁺/Tb³⁺-doped NPs with an AIEE dye designed for efficient energy transfer and attachment to the NPs produces a 2260-fold enhancement of multiphoton down-conversion by quantum cutting with remarkable photostability. In a prototypical application, the quantum cutting of UV photons to near-infrared photons that are matched to the band gap of a silicon solar cell produces an average 4% increase in efficiency under concentrated solar illumination. This provides a general strategy for NP photosensitization that can be applied to both multiphoton up- and down-conversion.

Molecular fluorescence-guided surgery of peritoneal carcinomatosis of colorectal origin: A narrative review

Patients with peritoneal carcinomatosis (PC) from colorectal origin may undergo cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC) as a curative approach. One major prognostic factor that affects survival is completeness of cytoreduction. Molecular Fluorescence Guided Surgery (MFGS) is a novel intraoperative imaging technique that may improve tumor identification in the future, potentially preventing over- and under-treatment in these patients. This narrative review outlines a chronological overview of MFGS development in patients with PC of colorectal origin.

Enzymatically activated reduction-caged SERS reporters for versatile bioassays

Here we report a facile strategy for activating reduction caged Raman reporters for surface-enhanced Raman scattering (SERS) with peroxidases. After selecting suitable caged reporters, versatile bioassays were developed. First, the bioassays for bioactive small molecules were developed. Then, the immunoassay was developed for C reactive protein (CRP), a biomarker for cardiovascular diseases.

Advances in Diagnostic and Intraoperative Molecular Imaging of Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) has a dismal prognosis. To improve outcomes, there is a critical need for improved tools for detection, accurate staging, and resectability assessment. This could improve patient stratification for the most optimal primary treatment modality. Molecular imaging, used in combination with tumor-specific imaging agents, can improve established imaging methods for PDAC. These novel, tumor-specific imaging agents developed to target specific biomarkers have the potential to specifically differentiate between malignant and benign diseases, such as pancreatitis. When these agents are coupled to various types of labels, this type of molecular imaging can provide integrated diagnostic, noninvasive imaging of PDAC as well as image-guided pancreatic surgery. This review provides a detailed overview of the current clinical imaging applications, upcoming molecular imaging strategies for PDAC, and potential targets for imaging, with an emphasis on intraoperative imaging applications.

Methods of Measuring Enzyme Activity Ex Vivo and In Vivo

Enzymes catalyze a variety of biochemical reactions in the body and, in conjunction with transporters and receptors, control virtually all physiological processes. There is great value in measuring enzyme activity ex vivo and in vivo. Spatial and temporal differences or changes in enzyme activity can be related to a variety of natural and pathological processes. Several analytical approaches have been developed to meet this need. They can be classified broadly as methods either based on artificial substrates, with the goal of creating images of diseased tissue, or based on natural substrates, with the goal of understanding natural processes. This review covers a selection of these methods, including optical, magnetic resonance, mass spectrometry, and physical sampling approaches, with a focus on creative chemistry and method development that make ex vivo and in vivo measurements of enzyme activity possible.

Image-guided surgery using near-infrared Turn-ON fluorescent nanoprobes for precise detection of tumor margins

Complete tumor removal during surgery has a great impact on patient survival. To that end, the surgeon should detect the tumor, remove it and validate that there are no residual cancer cells left behind. Residual cells at the incision margin of the tissue removed during surgery are associated with tumor recurrence and poor prognosis for the patient. In order to remove the tumor tissue completely with minimal collateral damage to healthy tissue, there is a need for diagnostic tools that will differentiate between the tumor and its normal surroundings. Methods: We designed, synthesized and characterized three novel polymeric Turn-ON probes that will be activated at the tumor site by cysteine cathepsins that are highly expressed in multiple tumor types. Utilizing orthotopic breast cancer and melanoma models, which spontaneously metastasize to the brain, we studied the kinetics of our polymeric Turn-ON nano-probes. Results: To date, numerous low molecular weight cathepsin-sensitive substrates have been reported, however, most of them suffer from rapid clearance and reduced signal shortly after administration. Here, we show an improved tumor-to-background ratio upon activation of our Turn-ON probes by cathepsins. The signal obtained from the tumor was stable and delineated the tumor boundaries during the whole surgical procedure, enabling accurate resection. Conclusions: Our findings show that the control groups of tumor-bearing mice, which underwent either standard surgery under white light only or under the fluorescence guidance of the commercially-available imaging agents ProSense® 680 or 5-aminolevulinic acid (5-ALA), survived for less time and suffered from tumor recurrence earlier than the group that underwent image-guided surgery (IGS) using our Turn-ON probes. Our "smart" polymeric probes can potentially assist surgeons' decision in real-time during surgery regarding the tumor margins needed to be removed, leading to improved patient outcome.

Multifunctional Magnetic Mesoporous Silica Nanoagents for in vivo Enzyme-Responsive Drug Delivery and MR Imaging

In this study, we report novel multifunctional nanoagents for in vivo enzyme-responsive anticancer drug delivery and magnetic resonance imaging (MRI), based on mesoporous silica coated iron oxide nanoparticles (Fe3O4@MSNs). The anticancer drug, DOX, was encapsulated in the porous cavities with a MMP-2 enzyme responsive peptide being covalently linked to the nanoparticles surface. The in vitro experiment results indicated that the enzyme responsive nanoagents own high specificity for controlled drug release in the cell line with high MMP-2 expression. Furthermore, the targeted delivery of the nanoagents to the tumor site purpose has been successfully achieved through magnet-guided nanocarrier accumulation by utilizing the magnetic properties of the Fe3O4 nanocores, which resulted in efficient inhibition of the tumor growth. Additionally, these novel nanoagents can also be used as MRI agent for the real-time diagnosis the tumor treatment process of living animals. Taking the advantages of high specificity, controllable drug release and real-time MRI imaging, we believe these multifunctional nanoagents could also be used as a general platform for the design of stimulus-responsive multifunctional nanomaterials for the aim of accurate diagnosis and efficient treatment of other diseases.

Deciphering Design Principles of Förster Resonance Energy Transfer-Based Protease Substrates: Thermolysin-Like Protease from Geobacillus stearothermophilus as a Test Case

Protease activity is frequently assayed using short peptides that are equipped with a Förster resonance energy transfer (FRET) reporter system. Many frequently used donor-acceptor pairs are excited in the ultraviolet range and suffer from low extinction coefficients and quantum yields, limiting their usefulness in applications where a high sensitivity is required. A large number of alternative chromophores are available that are excited in the visible range, for example, based on xanthene or cyanine core structures. These alternatives are not only larger in size but also more hydrophobic. Here, we show that the hydrophobicity of these chromophores not only affects the solubility of the resulting FRET-labeled peptides but also their kinetic parameters in a model enzymatic reaction. In detail, we have compared two series of 4-8 amino acid long peptides, designed to serve as substrates for the thermolysin-like protease (TLP-ste) from Geobacillus stearothermophilus. These peptides were equipped with a carboxyfluorescein donor and either Cy5 or its sulfonated derivative Alexa Fluor 647 as the acceptor. We show that the turnover rate k _cat is largely unaffected by the choice of the acceptor fluorophore, whereas the K _M value is significantly lower for the Cy5- than for the Alexa Fluor 647-labeled substrates. TLP-ste is a rather nonspecific protease with a large number of hydrophobic amino acids surrounding the catalytic site, so that the fluorophore itself may form additional interactions with the enzyme. This hypothesis is supported by the result that the difference between Cy5- and Alexa Fluor 647-labeled substrates becomes less pronounced with increasing peptide length, that is, when the fluorophore is positioned at a larger distance from the catalytic site. These results suggest that fluorophores may become an integral part of FRET-labeled peptide substrates and that K _M and k _cat values are generally only valid for a specific combination of the peptide sequence and FRET pair.

The effect of near-infrared fluorescence conjugation on the anti-cancer potential of cetuximab

This study investigated the anti-cancer potential of a near-infrared fluorescence (NIRF) molecule conjugated with Cetuximab (Cetuximab-NIRF) in six-week-old female BALB/c athymic (nu+/nu+) nude mice. A431 cells were cultured and injected into the animals to induce solid tumors. Paclitaxel (30 mg/kg body weight (BW)), Cetuximab (1 mg/kg BW), and Cetuximab-NIRF (0.25, 0.5 and 1.0 mg/kg BW) were intraperitoneally injected twice a week into the A431 cell xenografts of the nude mice. Changes in BW, tumor volume and weight, fat and lean mass, and diameter of the peri-tumoral blood vessel were determined after two weeks. Tumor volumes and weights were significantly decreased in the Cetuximab-NIRF (1 mg/kg BW) group compared with the control group (P<0.001). Lean mass and total body water content were also conspicuously reduced in the Cetuximab-NIRF (1 mg/kg BW) group compared with the vehicle control group. Peri-tumoral blood vessel diameters were very thin in the Cetuximab-NIRF groups compared with those of the paclitaxel group. These results indicate that the conjugation of Cetuximab with NIRF does not affect the anti-cancer potential of Cetuximab and NIRF can be used for molecular imaging in cancer treatments.

Synthesis of tri-functionalized MMP2 FRET probes using a chemo-selective and late-stage modification of unprotected peptides

A polymeric FRET probe for the detection of MMP2 was prepared using a new N-hydroxylamine derivative of lysine (1), which was successfully incorporated into the natural peptide sequence by solid phase peptide synthesis (SPPS). Following the attachment of a PEG group to the N-terminus, a peptide was cleaved from the resin. The fully-deprotected peptide-PEG conjugate was subsequently subjected to the α-ketoacid-hydroxylamine (KAHA) ligation and Michael addition of FRET donor (MCA) and acceptor (DNP) moieties, respectively. The successfully synthesized polymeric FRET probes with an MMP2-reactive peptide and a negative control peptide with a random sequence were subjected to an in vitro test with MMP2. This methodology under mild conjugation conditions of KAHA ligation can be applicable for the preparation of NIR probes with sensitive fluorophore moieties.

Optical molecular imaging for tumor detection and image-guided surgery

We have witnessed rapid development of fluorescence molecular imaging of solid tumors for cancer diagnosis and image-guided surgery in the past decade. Many biomarkers unique to cancer cells or tumor microenvironment, such as cell surface receptors, hypoxia, secreted proteases and extracellular acidosis have been characterized, and can be used to distinguish cancer from normal tissue. A variety of optical imaging probes have been developed to target these biomarkers to improve tumor contrast over the background tissue. Unlike conventional anatomical and molecular imaging technologies, fluorescent imaging method benefits from its safety, high-spatial resolution and real-time capability, and therefore, has become a highly adoptable imaging method for tumor detection and image-guided surgery in clinics. In this review, we summarize recent progress in 'always-ON' and stimuli-activatable fluorescent imaging probes, and discuss their potentials in tumor detection and image-guided surgery.

Long-term fluorescence lifetime imaging of a genetically encoded sensor for caspase-3 activity in mouse tumor xenografts

Caspase-3 is known for its role in apoptosis and programmed cell death regulation. We detected caspase-3 activation in vivo in tumor xenografts via shift of mean fluorescence lifetimes of a caspase-3 sensor. We used the genetically encoded sensor TR23K based on the red fluorescent protein TagRFP and chromoprotein KFP linked by 23 amino acid residues (TagRFP-23-KFP) containing a specific caspase cleavage DEVD motif to monitor the activity of caspase-3 in tumor xenografts by means of fluorescence lifetime imaging-Forster resonance energy transfer. Apoptosis was induced by injection of paclitaxel for A549 lung adenocarcinoma and etoposide and cisplatin for HEp-2 pharynx adenocarcinoma. We observed a shift in lifetime distribution from 1.6 to 1.9 ns to 2.1 to 2.4 ns, which indicated the activation of caspase-3. Even within the same tumor, the lifetime varied presumably due to the tumor heterogeneity and the different depth of tumor invasion. Thus, processing time-resolved fluorescence images allows detection of both the cleaved and noncleaved states of the TR23K sensor in real-time mode during the course of several weeks noninvasively. This approach can be used in drug screening, facilitating the development of new anticancer agents as well as improvement of chemotherapy efficiency and its adaptation for personal treatment.

Near-Infrared Fluorescent Nanoprobes for Revealing the Role of Dopamine in Drug Addiction

Brain imaging techniques enable visualizing the activity of central nervous system without invasive neurosurgery. Dopamine is an important neurotransmitter. Its fluctuation in brain leads to a wide range of diseases and disorders, like drug addiction, depression, and Parkinson's disease. We designed near-infrared fluorescence dopamine-responsive nanoprobes (DRNs) for brain activity imaging during drug abuse and addiction process. On the basis of light-induced electron transfer between DRNs and dopamine and molecular wire effect of the DRNs, we can track the dynamical change of the neurotransmitter level in the physiological environment and the releasing of the neurotransmitter in living dopaminergic neurons in response to nicotine stimulation. The functional near-infrared fluorescence imaging can dynamically track the dopamine level in the mice midbrain under normal or drug-activated condition and evaluate the long-term effect of addictive substances to the brain. This strategy has the potential for studying neural activity under physiological condition.

Fluorescence Detection of Cell Death in Liver of Mice Treated with Thioacetamide

The purpose of this study was to detect cell death in the liver of mice treated with thioacetamide (TAA) using fluorescence bioimaging and compare this outcome with that using conventional histopathological examination. At 6 weeks of age, 24 mice were randomly divided into three groups: group 1 (G1), control group; group 2 (G2), fluorescence probe control group; group 3 (G3), TAA-treated group. G3 mice were treated with TAA. Twenty-two hours after TAA treatment, G2 and G3 mice were treated with Annexin-Vivo 750. Fluorescence in vivo bioimaging was performed by fluorescence molecular tomography at two hours after Annexin-Vivo 750 treatment, and fluorescence ex vivo bioimaging of the liver was performed. Liver damage was validated by histopathological examination. In vivo bioimaging showed that the fluorescence intensity was increased in the right upper part of G3 mice compared with that in G2 mice, whereas G1 mice showed no signal. Additionally ex vivo bioimaging showed that the fluorescence intensity was significantly increased in the livers of G3 mice compared with those in G1 or G2 mice (p < 0.05). Histopathological examination of the liver showed no cell death in G1 and G2 mice. However, in G3 mice, there was destruction of hepatocytes and increased cell death. Terminal deoxynucleotidyl transferase dUTP nick end labeling staining confirmed many cell death features in the liver of G3 mice, whereas no pathological findings were observed in the liver of G1 and G2 mice. Taken together, fluorescence bioimaging in this study showed the detection of cell death and made it possible to quantify the level of cell death in male mice. The outcome was correlated with conventional biomedical examination. As it was difficult to differentiate histological location by fluorescent bioimaging, it is necessary to develop specific fluorescent dyes for monitoring hepatic disease progression and to exploit new bioimaging techniques without dye-labeling.

Polymer Therapeutics: Biomarkers and New Approaches for Personalized Cancer Treatment

Polymer therapeutics (PTs) provides a potentially exciting approach for the treatment of many diseases by enhancing aqueous solubility and altering drug pharmacokinetics at both the whole organism and subcellular level leading to improved therapeutic outcomes. However, the failure of many polymer-drug conjugates in clinical trials suggests that we may need to stratify patients in order to match each patient to the right PT. In this concise review, we hope to assess potential PT-specific biomarkers for cancer treatment, with a focus on new studies, detection methods, new models and the opportunities this knowledge will bring for the development of novel PT-based anti-cancer strategies. We discuss the various "hurdles" that a given PT faces on its passage from the syringe to the tumor (and beyond), including the passage through the bloodstream, tumor targeting, tumor uptake and the intracellular release of the active agent. However, we also discuss other relevant concepts and new considerations in the field, which we hope will provide new insight into the possible applications of PT-related biomarkers.

A fluorescent 3,7-bis-(naphthalen-1-ylethynylated)-2′-deoxyadenosine analogue reports thymidine in complementary DNA by a large emission Stokes shift

The first example of a fluorescent adenosine analogue possessing simultaneous major- and minor-groove substitution selectively reports base-pairing to thymidine.

Advanced Contrast Agents for Multimodal Biomedical Imaging Based on Nanotechnology

Clinical imaging modalities have reached a prominent role in medical diagnosis and patient management in the last decades. Different image methodologies as Positron Emission Tomography, Single Photon Emission Tomography, X-Rays, or Magnetic Resonance Imaging are in continuous evolution to satisfy the increasing demands of current medical diagnosis. Progress in these methodologies has been favored by the parallel development of increasingly more powerful contrast agents. These are molecules that enhance the intrinsic contrast of the images in the tissues where they accumulate, revealing noninvasively the presence of characteristic molecular targets or differential physiopathological microenvironments. The contrast agent field is currently moving to improve the performance of these molecules by incorporating the advantages that modern nanotechnology offers. These include, mainly, the possibilities to combine imaging and therapeutic capabilities over the same theranostic platform or improve the targeting efficiency in vivo by molecular engineering of the nanostructures. In this review, we provide an introduction to multimodal imaging methods in biomedicine, the sub-nanometric imaging agents previously used and the development of advanced multimodal and theranostic imaging agents based in nanotechnology. We conclude providing some illustrative examples from our own laboratories, including recent progress in theranostic formulations of magnetoliposomes containing ω-3 poly-unsaturated fatty acids to treat inflammatory diseases, or the use of stealth liposomes engineered with a pH-sensitive nanovalve to release their cargo specifically in the acidic extracellular pH microenvironment of tumors.

NIR-I-to-NIR-II fluorescent nanomaterials for biomedical imaging and cancer therapy

This review discusses the recent development of nanomaterials with NIR-I-to-NIR-II fluorescence and their applications in biomedical imaging and cancer therapy.

Single Pixel Black Phosphorus Photodetector for Near-Infrared Imaging

Infrared imaging systems have wide range of military or civil applications and 2D nanomaterials have recently emerged as potential sensing materials that may outperform conventional ones such as HgCdTe, InGaAs, and InSb. As an example, 2D black phosphorus (BP) thin film has a thickness-dependent direct bandgap with low shot noise and noncryogenic operation for visible to mid-infrared photodetection. In this paper, the use of a single-pixel photodetector made with few-layer BP thin film for near-infrared imaging applications is demonstrated. The imaging is achieved by combining the photodetector with a digital micromirror device to encode and subsequently reconstruct the image based on compressive sensing algorithm. Stationary images of a near-infrared laser spot (λ = 830 nm) with up to 64 × 64 pixels are captured using this single-pixel BP camera with 2000 times of measurements, which is only half of the total number of pixels. The imaging platform demonstrated in this work circumvents the grand challenges of scalable BP material growth for photodetector array fabrication and shows the efficacy of utilizing the outstanding performance of BP photodetector for future high-speed infrared camera applications.

Optimization of a Protease Activated Probe for Optical Surgical Navigation

Molecularly targeted optical contrast agents have the potential to enable surgeons to visualize specific molecular markers that can help improve surgical precision and thus outcomes. Fluorescently quenched substrates can be used to highlight tumor lesions by targeting proteases that are highly abundant in the tumor microenvironment. However, the majority of these and other molecularly targeted optical contrast agents are labeled with reporter dyes that are not ideally matched to the properties of clinical camera systems, which are typically optimized for detection of indocyanine-green (ICG). While a wide range of near-infrared (NIR) dyes are suitable for use with highly sensitive and highly tunable research-focused small animal imaging systems, most have not been evaluated for use with commonly used clinical imaging systems. Here we report the optimization of a small molecule fluorescently quenched protease substrate probe 6QC-ICG, which uses the indocyanine green (ICG) dye as its optical reporter. We evaluated dosing and kinetic parameters of this molecule in tumor-bearing mice and observed optimal tumor over background signals in as little as 90 min with a dose of 2.3 mg/kg. Importantly, the fluorescence intensity of the probe signal in tumors did not linearly scale with dose, suggesting the importance of detailed dosing studies. Furthermore, when imaged using the FDA approved da Vinci Si surgical system with Firefly detection, signals were significantly higher for the ICG probe compared to a corresponding probe containing a dye with similar quantum yield but with a slightly shifted excitation and emission profile. The increased signal intensity generated by the optimal dye and dose of the ICG labeled probe enabled detection of small, flat lesions that were less than 5 mm in diameter. Therefore, 6QC-ICG is a highly sensitive probe that performs optimally with clinical imaging systems and has great potential for applications in optical surgical navigation.

Engineered Livers for Infectious Diseases

Engineered liver systems come in a variety of platform models, from 2-dimensional cocultures of primary human hepatocytes and stem cell-derived progeny, to 3-dimensional organoids and humanized mice. Because of the species-specificity of many human hepatropic pathogens, these engineered systems have been essential tools for biologic discovery and therapeutic agent development in the context of liver-dependent infectious diseases. Although improvement of existing models is always beneficial, and the addition of a robust immune component is a particular need, at present, considerable progress has been made using this combination of research platforms. We highlight advances in the study of hepatitis B and C viruses and malaria-causing Plasmodium falciparum and Plasmodium vivax parasites, and underscore the importance of pairing the most appropriate model system and readout modality with the particular experimental question at hand, without always requiring a platform that recapitulates human physiology in its entirety.

Evaluation of a Centyrin-Based Near-Infrared Probe for Fluorescence-Guided Surgery of Epidermal Growth Factor Receptor Positive Tumors

Tumor-targeted near-infrared fluorescent dyes have the potential to improve cancer surgery by enabling surgeons to locate and resect more malignant lesions where good visualization tools are required to ensure complete removal of malignant tissue. Although the tumor-targeted fluorescent dyes used in humans to date have been either small organic molecules or high molecular weight antibodies, low molecular weight protein scaffolds have attracted significant attention because they penetrate solid tumors almost as efficiently as small molecules, but can be infinitely mutated to bind almost any antigen. Here we describe the use of a 10 kDa protein scaffold, a Centyrin, to target a near-infrared fluorescent dye to tumors that overexpress the epidermal growth factor receptor (EGFR) for fluorescence-guided surgery (FGS). We have developed and optimized the dose and time required for imaging small tumor burdens with minimal background fluorescence in real-time fluorescence-guided surgery of EGFR-expressing tumor xenografts in murine models. We demonstrate that the Centyrin-near-infrared dye conjugate (CNDC) binds selectively to human EGFR+ cancer cells with an EC50 of 2 nM, localizes to EGFR+ tumor xenografts in athymic nude mice and that uptake of the dye in xenografts is significantly reduced when EGFR are blocked by preinjection of excess unlabeled Centyrin. Taken together, these data suggest that CNDCs can be used for intraoperative identification and surgical removal of EGFR-expressing lesions and that Centyrins targeted to other tumor-specific antigens should prove similarly useful in fluorescence guided surgery of cancer. In addition, we demonstrate that the CNDC is detected in the NIR region of the spectrum and can be utilized for fluorescence-guided surgery (FGS). In addition, we propose that with its eventual complete clearance from EGFR-negative tissues and its quantitative retention in the tumor mass for >24 h, a Centyrin-targeted NIR dye should provide excellent tumor contrast when injected at least 6-8 h before initiation of cancer surgery in human patients.

Copper Manganese Sulfide Nanoplates: A New Two-Dimensional Theranostic Nanoplatform for MRI/MSOT Dual-Modal Imaging-Guided Photothermal Therapy in the Second Near-Infrared Window

Multifunctional nanoplatforms with integrated diagnostic and therapeutic functions have attracted tremendous attention. Especially, the second near-infrared (NIR-II) light response-based nanoplatforms hold great potential in cancer theranostic applications, which is because the NIR-II window provides larger tissue penetration depth and higher maximum permissible exposure (MPE) than that of the well-studied first near-infrared (NIR-I) window. Herein, we for the first time present a two-dimensional (2D)-nanoplatform based on Cu₂MnS₂ nanoplates (NPs) for magnetic resonance imaging (MRI)/multispectral optoacoustic tomography (MSOT) dual-modal imaging-guided photothermal therapy (PTT) of cancer in the NIR-II window. Methods: Cu₂MnS₂ NPs were synthesized through a facile and environmentally friendly process. A series of experiments, including the characterization of Cu₂MnS₂ NPs, the long-term toxicity of Cu₂MnS₂ NPs in BALB/c nude mice, the applications of Cu₂MnS₂ NPs for in vitro and in vivo MRI/MSOT dual-modal imaging and NIR-II PTT of cancer were carried out. Results: The as-synthesized Cu₂MnS₂ NPs exhibit low cytotoxicity, excellent biocompatibility as well as high photothermal conversion efficiency (~49.38%) and outstanding photostability. Together with their good T₁-shortening effect and strong absorbance in the NIR-I and NIR-II region, the Cu₂MnS₂ NPs display high-contrast imaging performance both in MRI and MSOT (900 nm laser source). Moreover, the subsequent in vitro and in vivo results demonstrate that the Cu₂MnS₂ NPs possess excellent PTT efficacy under 1064 nm laser irradiation with a low power density (0.6 W cm^-2). In addition, the detailed long-term toxicity studies further confirming the safety of Cu₂MnS₂ NPs in vivo. Conclusion: We have developed a new 2D Cu₂MnS₂ NPs as multifunctional theranostic agents for MRI/MSOT dual-modal imaging-guided PTT of cancer in the NIR-II window. Such biocompatible Cu₂MnS₂ NPs might provide a new perspective for exploring new 2D-based nanoplatforms with improved properties for clinical applications in the future.

Near-Infrared Trigged Stimulus-Responsive Photonic Crystals with Hierarchical Structures

Stimuli-responsive photonic crystals (PCs) trigged by light would provide a novel intuitive and quantitative method for noninvasive detection. Inspired by the flame-detecting aptitude of fire beetles and the hierarchical photonic structures of butterfly wings, we herein developed near-infrared stimuli-responsive PCs through coupling photothermal Fe₃O₄ nanoparticles with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM), with hierarchical photonic structured butterfly wing scales as the template. The nanoparticles within 10 s transferred near-infrared radiation into heat that triggered the phase transition of PNIPAM; this almost immediately posed an anticipated effect on the PNIPAM refractive index and resulted in a composite spectrum change of ∼26 nm, leading to the direct visual readout. It is noteworthy that the whole process is durable and stable mainly owing to the chemical bonding formed between PNIPAM and the biotemplate. We envision that this biologically inspired approach could be utilized in a broad range of applications and would have a great impact on various monitoring processes and medical sensing.

Enzyme-Targeted Nanoparticles for Delivery to Ischemic Skeletal Muscle

The targeted delivery of enzyme-responsive nanoparticles to specific tissues can be a valuable, minimally invasive approach for imaging or drug delivery applications. In this study, we show for the first time enzyme-directed assembly of intravenously (IV) delivered nanoparticles in ischemic skeletal muscle, which has applications for drug delivery to damaged muscle of the type prevalent in peripheral artery disease (PAD). Specifically, micellar nanoparticles are cleavable by matrix metalloproteinases (MMPs), causing them to undergo a morphological switch and thus aggregate in tissues where these enzymes are upregulated, like ischemic muscle. Here, we demonstrated noninvasive in vivo imaging of these IV-injected nanoparticles through near-infrared dye labeling and in vivo imaging (IVIS) particle tracking in a rat hindlimb ischemia model. Polymer peptide amphiphilic nanoparticles were synthesized and optimized for both MMP cleavage efficiency and near-IR fluorescence. Nanoparticles were injected 4 days after unilateral hindlimb ischemia and were monitored over 28 days using IVIS imaging. Nanoparticles targeted to ischemic muscle over healthy muscle, and ex vivo biodistribution analysis at 7 and 28 days post-injection confirmed targeting to the ischemic muscle as well as off target accumulation in the liver and spleen. Ex vivo histology confirmed particle localization in ischemic but not healthy muscle. Altering the surface charge of the nanoparticles through addition of zwitterionic dye species resulted in improved targeting to the ischemic muscle. To our knowledge, this is the first study to demonstrate the targeted delivery and long term retention of nanoparticles using an enzyme-directed morphology switch. This has implications for noninvasive drug delivery vehicles for treating ischemic muscle, as no minimally invasive, non-surgical options currently exist.

An optical probe for detecting chondrocyte apoptosis in response to mechanical injury

Cartilage injury induced by acute excessive contact stress is common and mostly affects young adult. Although early detection of cartilage injury may prevent serious and lifelong arthritic complications, early detection and treatment is not possible due to the lack of a reliable detection method. Since chondrocyte injury and subsequent cell death are the early signs of cartilage injury, it is likely that cartilage cell apoptosis can be used to predict the extent of injury. To test this hypothesis, a near infrared probe was fabricated to have high affinity to apoptotic cells. In vitro tests show that this apoptosis probe has low toxicity, high specificity, and high affinity to apoptotic cells. In addition, there is a positive relationship between apoptotic cell numbers and fluorescence intensities. Using a mouse xiphoid injury model, we found significant accumulation of the apoptosis probes at the injured xiphoid cartilage site. There was also a positive correlation between probe accumulation and the number of apoptotic chondrocytes within the injured xiphoid cartilage, which was confirmed by TUNEL assay. The results support that the apoptosis probes may serve as a powerful tool to monitor the extent of mechanical force-induced cartilage injury in vivo.

Intracellular Proteolytic Disassembly of Self-Quenched Near-Infrared Nanoparticles Turning Fluorescence on for Tumor-Targeted Imaging

The design of tumor-targeting, intracellular protease-activatable near-infrared fluorescence (NIRF) nanoprobes is broadly interesting but remains challenging. In this work, we report the rational design of a NIR probe Cys(StBu)-Lys(Biotin)-Lys-Lys(Cy5.5)-CBT (1) to facilely prepare the self-quenched nanoparticles 1-NPs for tumor-targeted imaging in vitro and in vivo. The biotinylated 1-NPs could be actively uptaken by biotin receptor-overexpressing tumor cells via receptor-mediated endocytosis. Upon intracellular proteolytic cleavage, 1-NPs were disassembled to yield the small molecular probe Lys(Cy5.5)-Luciferin-Lys(Biotin)-Lys-OH (1-D-cleaved), accompanied by fluorescence "Turn-On". With this NIRF "Turn-On" property, 1-NPs were successfully applied for tumor-targeted imaging. We envision that our nanoparticles could be applied for fluorescence-guided tumor surgery in the near future.