pHLIP ICG for delineation of tumors and blood flow during fluorescence-guided surgery

A pan-cancer dye for solid-tumour screening, resection and wound monitoring via short-wave and near-infrared fluorescence imaging

The efficacy of fluorescence-guided surgery in facilitating the real-time delineation of tumours depends on the optical contrast of tumour tissue over healthy tissue. Here we show that CJ215-a commercially available, renally cleared carbocyanine dye sensitive to apoptosis, and with an absorption and emission spectra suitable for near-infrared fluorescence imaging (wavelengths of 650-900 nm) and shortwave infrared (SWIR) fluorescence imaging (900-1,700 nm)-can facilitate fluorescence-guided tumour screening, tumour resection and the assessment of wound healing. In tumour models of either murine or human-derived breast, prostate and colon cancers and of fibrosarcoma, and in a model of intraperitoneal carcinomatosis, imaging of CJ215 with ambient light allowed for the delineation of nearly all tumours within 24 h after intravenous injection of the dye, which was minimally taken up by healthy organs. At later timepoints, CJ215 provided tumour-to-muscle contrast ratios up to 100 and tumour-to-liver contrast ratios up to 18. SWIR fluorescence imaging with the dye also allowed for quantifiable non-contact wound monitoring through commercial bandages. CJ215 may be compatible with existing and emerging clinical solutions.

Hyaluronic acid modified indocyanine green nanoparticles: a novel targeted strategy for NIR-II fluorescence lymphatic imaging

The lymphatic system, alongside blood circulation, is crucial for maintaining bodily equilibrium and immune surveillance. Despite its importance, lymphatic imaging techniques lag behind those for blood circulation. Fluorescence imaging, particularly in the near-infrared-II (NIR-II) region, offers promising capabilities with centimeter-scale tissue penetration and micron-scale spatial resolution, sparking interest in visualizing the lymphatic system. Although indocyanine green (ICG) has been approved by the Food and Drug Administration (FDA) for use as a near-infrared-I (NIR-I) region fluorescent dye, its limitations include shallow penetration depth and low signal-to-noise ratio. Research suggests that ICG's fluorescence emission tail in the second near-infrared window holds potential for high-quality NIR-II imaging. However, challenges like short circulation half-life and concentration-dependent aggregation hinder its wider application. Here we developed HA@ICG nanoparticles (NPs), a superior ICG-based NIR-II fluorescent probe with excellent biocompatibility, prolonging in vivo imaging, and enhancing photostability compared to ICG alone. Leveraging LYVE-1, a prominent lymphatic endothelial cell receptor that binds specifically to hyaluronic acid (HA), our nanoprobes exhibit exceptional performance in targeting lymphatic system imaging. Moreover, our findings demonstrate the capability of HA@ICG NPs for capillary imaging, offering a means to assess local microcirculatory blood supply. These compelling results underscore the promising potential of HA@ICG NPs for achieving high-resolution bioimaging of nanomedicines in the NIR-II window.

Astrocytic Slc4a4 regulates blood-brain barrier integrity in healthy and stroke brains via a CCL2-CCR2 pathway and NO dysregulation

Astrocytes play vital roles in blood-brain barrier (BBB) maintenance, yet how they support BBB integrity under normal or pathological conditions remains poorly defined. Recent evidence suggests that ion homeostasis is a cellular mechanism important for BBB integrity. In the current study, we investigated the function of an astrocyte-specific pH regulator, Slc4a4, in BBB maintenance and repair. We show that astrocytic Slc4a4 is required for normal astrocyte morphological complexity and BBB function. Multi-omics analyses identified increased astrocytic secretion of CCL2 coupled with dysregulated arginine-NO metabolism after Slc4a4 deletion. Using a model of ischemic stroke, we found that loss of Slc4a4 exacerbates BBB disruption, which was rescued by pharmacological or genetic inhibition of the CCL2-CCR2 pathway in vivo. Together, our study identifies the astrocytic Slc4a4-CCL2 and endothelial CCR2 axis as a mechanism controlling BBB integrity and repair, while providing insights for a therapeutic approach against BBB-related CNS disorders.

pHLIP targeted intracellular delivery of calicheamicin

Calicheamicin is a potent, cell-cycle independent enediyne antibiotic that binds and cleaves DNA. Toxicity has led to its use in a targeted form, as an antibody-drug conjugate approved for the treatment of liquid tumors. We used a reduced calicheamicin to conjugate it to a single cysteine residue at the membrane-inserting end of a pH Low Insertion Peptide (pHLIP) that targets imaging and therapeutic agents to tumors. The cytoplasmic reduction of the disulfide releases the calicheamicin, and activation, DNA binding, and strand scission ensue. We studied the interaction of pHLIP-calicheamicin with liposomal and cellular membranes and demonstrated that the agent exhibits cytotoxic activity both in highly proliferative cancer cells and in non-proliferative immune cells, such as polarized M2 macrophages. In vivo, the agent was effective in inhibiting tumor growth in mice with no signs of toxicity. Biodistribution studies confirmed tumor targeting with no accumulation of the agent in organs and tissues. The agent was found within the tumor mass and tumor-stroma interface. Treatment of tumors led to the depletion of CD206+ M2- tumor-associated macrophages within the tumor core. pHLIP-calicheamicin could be pursued as an effective therapeutic for the treatment of solid tumors.

Targeted intracellular delivery of dimeric STINGa by two pHLIP peptides for treatment of solid tumors

Introduction: We have developed a delivery approach that uses two pHLIP peptides that collaborate in the targeted intracellular delivery of a single payload, dimeric STINGa (dMSA). Methods: dMSA was conjugated with two pHLIP peptides via S-S cleavable self-immolating linkers to form 2pHLIP-dMSA. Results: Biophysical studies were carried out to confirm pH-triggered interactions of the 2pHLIP-dMSA with membrane lipid bilayers. The kinetics of linker self-immolation and dMSA release, the pharmacokinetics, the binding to plasma proteins, the stability of the agent in plasma, the targeting and resulting cytokine activation in tumors, and the biodistribution of the construct was investigated. This is the first study demonstrating that combining the energy of the membrane-associated folding of two pHLIPs can be utilized to enhance the targeted intracellular delivery of large therapeutic cargo payloads. Discussion: Linking two pHLIPs to the cargo extends blood half-life, and targeted delivery of dimeric STINGa induces tumor eradication and the development of robust anti-cancer immunity.

A pan-cancer agent for screening, resection and wound monitoring via NIR and SWIR imaging

Fluorescence guided surgery (FGS) facilitates real time tumor delineation and is being rapidly established clinically. FGS efficacy is tied to the utilized dye and provided tumor contrast over healthy tissue. Apoptosis, a cancer hallmark, is a desirable target for tumor delineation. Here, we preclinically in vitro and in vivo, validate an apoptosis sensitive commercial carbocyanine dye (CJ215), with absorption and emission spectra suitable for near infrared (NIR, 650-900nm) and shortwave infrared (SWIR, 900-1700nm) fluorescence imaging (NIRFI, SWIRFI). High contrast SWIRFI for solid tumor delineation is demonstrated in multiple murine and human models including breast, prostate, colon, fibrosarcoma and intraperitoneal colorectal metastasis. Organ necropsy and imaging highlighted renal clearance of CJ215. SWIRFI and CJ215 delineated all tumors under ambient lighting with a tumor-to-muscle ratio up to 100 and tumor-to-liver ratio up to 18, from 24 to 168 h post intravenous injection with minimal uptake in healthy organs. Additionally, SWIRFI and CJ215 achieved non-contact quantifiable wound monitoring through commercial bandages. CJ215 provides tumor screening, guided resection, and wound healing assessment compatible with existing and emerging clinical solutions.

Head-to-head comparison of in vitro and in vivo efficacy of pHLIP-conjugated anti-seed gamma peptide nucleic acids

Gamma peptide nucleic acids (γPNAs) have recently garnered attention in diverse therapeutic and diagnostic applications. Serine and diethylene-glycol-containing γPNAs have been tested for numerous RNA-targeting purposes. Here, we comprehensively evaluated the in vitro and in vivo efficacy of pH-low insertion peptide (pHLIP)-conjugated serine and diethylene-based γPNAs. pHLIP targets only the acidic tumor microenvironment and not the normal cells. We synthesized and parallelly tested pHLIP-serine γPNAs and pHLIP-diethylene glycol γPNAs that target the seed region of microRNA-155, a microRNA that is upregulated in various cancers. We performed an all-atom molecular dynamics simulation-based computational study to elucidate the interaction of pHLIP-γPNA constructs with the lipid bilayer. We also determined the biodistribution and efficacy of the pHLIP constructs in the U2932-derived xenograft model. Overall, we established that the pHLIP-serine γPNAs show superior results in vivo compared with the pHLIP-diethylene glycol-based γPNA.

D-to-E and T19V Variants of the pH-Low Insertion Peptide and Their Doxorubicin Conjugates Interact with Membrane at Higher pH Ranges Than WT

To improve targeted cargo delivery to cancer cells, pH-Low Insertion Peptide (pHLIP) variants were developed to interact with the membrane at pH values higher than those of the WT. The Asp-to-Glu variants aim to increase side chain pKa without disturbing the sequence of protonations that underpin membrane insertion. The Thr19 variants represent efforts to perturb the critical Pro20 residue. To study the effect of cargo on pHLIP insertion, doxorubicin (Dox), a fluorescent antineoplastic drug, was conjugated to selected variants near the inserting C-terminus. Variants and conjugates were characterized on a POPC membrane using Trp and Dox fluorescence methods to define the entire pH range of insertion (pHinitial-pHfinal). Compared to WT with a pHi-pHf range of 6.7-5.6, D25E-D31E-D33E, D14E-D25E-D31E-D33E, and T19V-D25E variants demonstrated higher pHi-pHf ranges of 7.3-6.1, 7.3-6.3, and 8.2-5.4, respectively. The addition of Dox expanded the pHi-pHf range, mainly by shifting pHi to higher pH values (e.g., WT pHLIP-Dox has a pHi-pHf range of 7.7-5.2). Despite the low Hill coefficient observed for the conjugates, D14E-D25E-D31E-D33E pHLIP-Dox completed insertion by a pHf of 5.7. However, the Dox cargo remained in the hydrophobic membrane interior after pHLIP insertion, which may impede drug release. Finally, a logistic function can describe pHLIP insertion as a peripheral-to-TM (start-to-finish) two-state transition; wherever possible, we discuss data deviating from such sigmoidal fitting in support of the idea that pH-specific intermediate states distinct from the initial peripheral state and the final TM state exist at intervening pH values.

Ambient Light Resistant Shortwave Infrared Fluorescence Imaging for Preclinical Tumor Delineation via the pH Low-Insertion Peptide Conjugated to Indocyanine Green

Shortwave infrared (900-1,700 nm) fluorescence imaging (SWIRFI) has shown significant advantages over visible (400-650 nm) and near-infrared (700-900 nm) fluorescence imaging (reduced autofluorescence, improved contrast, tissue resolution, and depth sensitivity). However, there is a major lag in the clinical translation of preclinical SWIRFI systems and targeted SWIRFI probes. Methods: We preclinically show that the pH low-insertion peptide conjugated to indocyanine green (pHLIP ICG), currently in clinical trials, is an excellent candidate for cancer-targeted SWIRFI. Results: pHLIP ICG SWIRFI achieved picomolar sensitivity (0.4 nM) with binary and unambiguous tumor screening and resection up to 96 h after injection in an orthotopic breast cancer mouse model. SWIRFI tumor screening and resection had ambient light resistance (possible without gating or filtering) with outstanding signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) values at exposures from 10 to 0.1 ms. These SNR and CNR values were also found for the extended emission of pHLIP ICG in vivo (>1,100 nm, 300 ms). Conclusion: SWIRFI sensitivity and ambient light resistance enabled continued tracer clearance tracking with unparalleled SNR and CNR values at video rates for tumor delineation (achieving a tumor-to-muscle ratio above 20). In total, we provide a direct precedent for the democratic translation of an ambient light resistant SWIRFI and pHLIP ICG ecosystem, which can instantly improve tumor resection.

Micro-engineering and nano-engineering approaches to investigate tumour ecosystems

The interactions among tumour cells, the tumour microenvironment (TME) and non-tumour tissues are of interest to many cancer researchers. Micro-engineering approaches and nanotechnologies are under extensive exploration for modelling these interactions and measuring them in situ and in vivo to investigate therapeutic vulnerabilities in cancer and extend a systemic view of tumour ecosystems. Here we highlight the greatest opportunities for improving the understanding of tumour ecosystems using microfluidic devices, bioprinting or organ-on-a-chip approaches. We also discuss the potential of nanosensors that can transmit information from within the TME or elsewhere in the body to address scientific and clinical questions about changes in chemical gradients, enzymatic activities, metabolic and immune profiles of the TME and circulating analytes. This Review aims to connect the cancer biology and engineering communities, presenting biomedical technologies that may expand the methodologies of the former, while inspiring the latter to develop approaches for interrogating cancer ecosystems.

pHLIP Peptides Target Acidity in Activated Macrophages

PURPOSE

Acidity can be a useful alternative biomarker for the targeting of metabolically active cells in certain diseased tissues, as in acute inflammation or aggressive tumors. We investigated the targeting of activated macrophages by pH low insertion peptides (pHLIPs), an established technology for targeting cell-surface acidity.

PROCEDURES

The uptake of fluorescent pHLIPs by activated macrophages was studied in cell cultures, in a mouse model of lung inflammation, and in a mouse tumor model. Fluorescence microscopy, whole-body and organ imaging, immunohistochemistry, and FACS analysis were employed.

RESULTS

We find that cultured, activated macrophages readily internalize pHLIPs. The uptake is higher in glycolytic macrophages activated by LPS and INF-γ compared to macrophages activated by IL-4/IL-13. Fluorescent pHLIPs target LPS-induced lung inflammation in mice. In addition to marking cancer cells within the tumor microenvironment, fluorescent pHLIPs target CD45+, CD11b+, F4/80+, and CD206+ tumor-associated macrophages with no significant targeting of other immune cells. Also, fluorescent pHLIPs target CD206-positive cells found in the inguinal lymph nodes of animals inoculated with breast cancer cells in mammary fat pads.

CONCLUSIONS

pHLIP peptides sense low cell surface pH, which triggers their insertion into the cell membrane. Unlike cancerous cells, activated macrophages do not retain inserted pHLIPs on their surfaces, instead their highly active membrane recycling moves the pHLIPs into endosomes. Targeting activated macrophages in diseased tissues may enable clinical visualization and therapeutic opportunities.

Imaging perfusion changes in oncological clinical applications by hyperspectral imaging: a literature review

BACKGROUND

Hyperspectral imaging (HSI) is a promising imaging modality that uses visible light to obtain information about blood flow. It has the distinct advantage of being noncontact, nonionizing, and noninvasive without the need for a contrast agent. Among the many applications of HSI in the medical field are the detection of various types of tumors and the evaluation of their blood flow, as well as the healing processes of grafts and wounds. Since tumor perfusion is one of the critical factors in oncology, we assessed the value of HSI in quantifying perfusion changes during interventions in clinical oncology through a systematic review of the literature.

MATERIALS AND METHODS

The PubMed and Web of Science electronic databases were searched using the terms "hyperspectral imaging perfusion cancer" and "hyperspectral imaging resection cancer". The inclusion criterion was the use of HSI in clinical oncology, meaning that all animal, phantom, ex vivo, experimental, research and development, and purely methodological studies were excluded.

RESULTS

Twenty articles met the inclusion criteria. The anatomic locations of the neoplasms in the selected articles were as follows: kidneys (1 article), breasts (2 articles), eye (1 article), brain (4 articles), entire gastrointestinal (GI) tract (1 article), upper GI tract (5 articles), and lower GI tract (6 articles).

CONCLUSIONS

HSI is a potentially attractive imaging modality for clinical application in oncology, with assessment of mastectomy skin flap perfusion after reconstructive breast surgery and anastomotic perfusion during reconstruction of gastrointenstinal conduit as the most promising at present.

Multiplexed Imaging Reveals the Spatial Relationship of the Extracellular Acidity-Targeting pHLIP with Necrosis, Hypoxia, and the Integrin-Targeting cRGD Peptide

pH (low) insertion peptides (pHLIPs) have been developed for cancer imaging and therapy targeting the acidic extracellular microenvironment. However, the characteristics of intratumoral distribution (ITD) of pHLIPs are not yet fully understood. This study aimed to reveal the details of the ITD of pHLIPs and their spatial relationship with other tumor features of concern. The fluorescent dye-labeled pHLIPs were intravenously administered to subcutaneous xenograft mouse models of U87MG and IGR-OV1 expressing αVβ3 integrins (using large necrotic tumors). The αVβ3 integrin-targeting Cy5.5-RAFT-c(-RGDfK-)4 was used as a reference. In vivo and ex vivo fluorescence imaging, whole-tumor section imaging, fluorescence microscopy, and multiplexed fluorescence colocalization analysis were performed. The ITD of fluorescent dye-labeled pHLIPs was heterogeneous, having a high degree of colocalization with necrosis. A direct one-to-one comparison of highly magnified images revealed the cellular localization of pHLIP in pyknotic, karyorrhexis, and karyolytic necrotic cells. pHLIP and hypoxia were spatially contiguous but not overlapping cellularly. The hypoxic region was found between the ITDs of pHLIP and the cRGD peptide and the Ki-67 proliferative activity remained detectable in the pHLIP-accumulated regions. The results provide a better understanding of the characteristics of ITD of pHLIPs, leading to new insights into the theranostic applications of pHLIPs.

Eradication of tumors and development of anti-cancer immunity using STINGa targeted by pHLIP

Despite significant progress in the development of novel STING agonists (STINGa), applications appear to be challenged by the low efficiency and poor selectivity of these agents. A pH Low Insertion Peptide (pHLIP) extends the lifetime of a STINGa in the blood and targets it to acidic cancer-associated fibroblasts (CAFs), tumor-associated macrophages (TAMs), myeloid derived suppressor cells (mMDSCs) and dendritic cells (DCs). CAFs constitute 25% of all live cells within CT26 tumors, and M2-type TAMs and mMDSCs are the most abundant among the immune cells. The resulting activation of cytokines within the tumor microenvironment (TME) triggers the eradication of small (100 mm³) and large (400-700 mm³) CT26 tumors in mice after a single dose of pHLIP-STINGa. The tumor stroma was destroyed (the number of CAFs was reduced by 98%), intratumoral hemorrhage developed, and the level of acidity within the TME was reduced. Further, no tumors developed in 20 out of 25 tumor-free mice re-challenged by an additional injection of cancer cells. The therapeutic effect on CT26 tumors was insignificant in nude mice, lacking T-cells. Thus, targeted delivery of STINGa to tumor stroma and TAMs induces activation of signaling, potentially resulting in the recruitment and infiltration of T-cells, which gain access to the tumor core. The cytotoxic activity of T-cells is not impaired by an acidic environment and immune memory is developed.

Ca2+ -dependent interactions between lipids and the tumor-targeting peptide pHLIP

Cancerous tissues undergo extensive changes to their cellular environments that differentiate them from healthy tissues. These changes include changes in extracellular pH and Ca2+ concentrations, and the exposure of phosphatidylserine (PS) to the extracellular environment, which can modulate the interaction of peptides and proteins with the plasma membrane. Deciphering the molecular mechanisms of such interactions is critical for advancing the knowledge-based design of cancer-targeting molecular tools, such as pH-low insertion peptide (pHLIP). Here, we explore the effects of PS, Ca2+ , and peptide protonation state on the interactions of pHLIP with lipid membranes. Cellular studies demonstrate that exposed PS on the plasma membrane promotes pHLIP targeting. The magnitude of this effect is dependent on extracellular Ca2+ concentration, indicating that divalent cations play an important role in pHLIP targeting in vivo. The targeting mechanism is further explored with a combination of fluorescence and circular dichroism experiments in model membranes and microsecond-timescale all-atom molecular dynamics simulations. Our results demonstrate that Ca2+ is engaged in coupling peptide-lipid interactions in the unprotonated transmembrane conformation of pHLIP. The simulations reveal that while the pH-induced insertion leads to a strong depletion of PS around pHLIP, the Ca2+ -induced insertion has the opposite effect. Thus, extracellular levels of Ca2+ are crucial to linking cellular changes in membrane lipid composition with the selective targeting and insertion of pHLIP. The characterized Ca2+ -dependent coupling between pHLIP sidechains and PS provides atomistic insights into the general mechanism for lipid-coupled regulation of protein-membrane insertion by divalent cations.

PET Imaging of Acidic Tumor Environment With 89Zr-labeled pHLIP Probes

Acidosis of the tumor microenvironment is a hallmark of tumor progression and has emerged as an essential biomarker for cancer diagnosis, prognosis, and evaluation of treatment response. A tool for quantitatively visualizing the acidic tumor environment could significantly advance our understanding of the behavior of aggressive tumors, improving patient management and outcomes. 89Zr-labeled pH-low insertion peptides (pHLIP) are a class of radiopharmaceutical imaging probes for the in vivo analysis of acidic tumor microenvironments via positron emission tomography (PET). Their unique structure allows them to sense and target acidic cancer cells. In contrast to traditional molecular imaging agents, pHLIP's mechanism of action is pH-dependent and does not rely on the presence of tumor-specific molecular markers. In this study, one promising acidity-imaging PET probe ([89Zr]Zr-DFO-Cys-Var3) was identified as a candidate for clinical translation.

Nontoxic Tumor-Targeting Optical Agents for Intraoperative Breast Tumor Imaging

Precise identification of the tumor margins during breast-conserving surgery (BCS) remains a challenge given the lack of visual discrepancy between malignant and surrounding normal tissues. Therefore, we developed a fluorescent imaging agent, ICG-p28, for intraoperative imaging guidance to better aid surgeons in achieving negative margins in BCS. Here, we determined the pharmacokinetics (PK), biodistribution, and preclinical toxicity of ICG-p28. The PK and biodistribution of ICG-p28 indicated rapid tissue uptake and localization at tumor lesions. There were no dose-related effect and no significant toxicity in any of the breast cancer and normal cell lines tested. Furthermore, ICG-p28 was evaluated in clinically relevant settings with transgenic mice that spontaneously developed invasive mammary tumors. Intraoperative imaging with ICG-p28 showed a significant reduction in the tumor recurrence rate. This simple, nontoxic, and cost-effective method can offer a new approach that enables surgeons to intraoperatively identify tumor margins and potentially improves overall outcomes by reducing recurrence rates.

ES-MION-Based Dual-Modality PET/MRI Probes for Acidic Tumor Microenvironment Imaging

Among all characteristics of the tumor microenvironment (TME), which are caused by abnormal proliferation of solid tumors, extracellular acidity is an important indicator for malignancy grading. pH-low insertion peptides (pHLIPs) are adopted to discern the acidic TME. To date, different imaging agents including fluorescent, positron emission tomography (PET), single photon emission computed tomography (SPECT), and magnetic resonance (MR) contrast agents with pHLIPs to target the acidic TME have been used to image various tumor models successfully. In this article, a PET/MRI dual-modality probe, based on extremely small magnetic iron oxide nanoparticles (ES-MIONs) with pHLIPs as a targeting unit, was proposed for the first time. In the phantom study, the probe showed relatively high r 1 relaxivity (r 1 = 1.03 mM-1 s-1), indicating that it could be used as a T1-weighted MR contrast agent. The 68Ga-radiolabeled probe was further studied in vitro and in vivo to evaluate pHLIP targeting efficacy and feasibility for PET/MRI. PET with intratumoral injection and T1-weighted MRI with intravenous injection both showed pHLIP-specific delivery of the probe. Therefore, we successfully designed and developed a radiolabeled ES-MION-based dual-modality PET/MRI agent to target the acidic tumor microenvironment. Although the accumulation of the probe in tumors with intravenous injection was not high enough to exhibit signals in the PET imaging study, our study still provides further insights into the ES-MION-based PET/MRI strategy.

The bright future of nanotechnology in lymphatic system imaging and imaging-guided surgery

Lymphatic system is identified the second vascular system after the blood circulation in mammalian species, however the research on lymphatic system has long been hampered by the lack of comprehensive imaging modality. Nanomaterials have shown the potential to enhance the quality of lymphatic imaging due to the unparalleled advantages such as the specific passive targeting and efficient co-delivery of cocktail to peripheral lymphatic system, ease molecular engineering for precise active targeting and prolonged retention in the lymphatic system of interest. Multimodal lymphatic imaging based on nanotechnology provides a complementary means to understand the kinetics of lymphoid tissues and quantify its function. In this review, we introduce the established approaches of lymphatic imaging used in clinic and summarize their strengths and weaknesses, and list the critical influence factors on lymphatic imaging. Meanwhile, the recent developments in the field of pre-clinical lymphatic imaging are discussed to shed new lights on the design of new imaging agents, the improvement of delivery methods and imaging-guided surgery strategies.

NIR-II emissive AIEgen photosensitizers enable ultrasensitive imaging-guided surgery and phototherapy to fully inhibit orthotopic hepatic tumors

Accurate diagnosis and effective treatment of primary liver tumors are of great significance, and optical imaging has been widely employed in clinical imaging-guided surgery for liver tumors. The second near-infrared window (NIR-II) emissive AIEgen photosensitizers have attracted a lot of attention with higher-resolution bioimaging and deeper penetration. NIR-II aggregation-induced emission-based luminogen (AIEgen) photosensitizers have better phototherapeutic effects and accuracy of the image-guided surgery/phototherapy. Herein, an NIR-II AIEgen phototheranostic dot was proposed for NIR-II imaging-guided resection surgery and phototherapy for orthotopic hepatic tumors. Compared with indocyanine green (ICG), the AIEgen dots showed bright and sharp NIR-II emission at 1250 nm, which extended to 1600 nm with high photostability. Moreover, the AIEgen dots efficiently generated reactive oxygen species (ROS) for photodynamic therapy. Investigations of orthotopic liver tumors in vitro and in vivo demonstrated that AIEgen dots could be employed both for imaging-guided tumor surgery of early-stage tumors and for 'downstaging' intention to reduce the size. Moreover, the therapeutic strategy induced complete inhibition of orthotopic tumors without recurrence and with few side effects.

Targeting the Hypoxic and Acidic Tumor Microenvironment with pH-Sensitive Peptides

The delivery of cancer therapeutics can be limited by pharmacological issues such as poor bioavailability and high toxicity to healthy tissue. pH-low insertion peptides (pHLIPs) represent a promising tool to overcome these limitations. pHLIPs allow for the selective delivery of agents to tumors on the basis of pH, taking advantage of the acidity of the hypoxic tumor microenvironment. This review article highlights the various applications in which pHLIPs have been utilized for targeting and treating diseases in hypoxic environments, including delivery of small molecule inhibitors, toxins, nucleic acid analogs, fluorescent dyes, and nanoparticles.