Molecular Regulation of Polymeric Raman Probes for Ultrasensitive Microtumor Diagnosis and Noninvasive Microvessle Imaging.

Raman imaging is a powerful tool for the diagnosis of cancers and visualization of various biological processes. Polymers possessing excellent biocompatibility are promising probes for Raman imaging. However, few polymers are reported to serve as Raman probes for in vivo imaging, mainly due to the intrinsic weak Raman signal intensity and fluorescence interference of these polymers. Herein, a poly(indacenodithiophene-benzothiadiazole) (IDT-BT) polymer is presented, which emits unprecedentedly strong Raman signals under the near-infrared wavelength (785 nm) excitation, thus functioning as a Raman probe for ultrasensitive in vivo Raman imaging. Further mechanistic studies unveil that the unique Raman feature of the IDT-BT polymer relies on molecularly regulating its absorbance edge adjacent to the desired excitation wavelength, thus avoiding fluorescence interference and simultaneously emitting strong Raman scattering under preresonant excitation. Taking advantage of this discipline, the IDT-BT polymeric probe successfully realizes intraoperative Raman imaging of micrometastasis as small as 0.3 mm × 0.3 mm, comparable to the most sensitive Raman probes currently reported. Impressively, the IDT-BT enables noninvasive microvascular imaging, which is not achieved using other Raman probes. This work opens a new avenue toward the development of polymeric Raman probes for in vivo Raman imaging.

Ultrasensitive Exosome Detection by Modularized SERS Labeling for Postoperative Recurrence Surveillance.

Exosome-based liquid biopsy holds great potential in monitoring tumor progression. Current exosome detection biosensors rely on signal amplification strategies to improve sensitivity; however, these strategies pay little attention to manipulating the number of signal reporters, limiting the rational optimization of the biosensors. Here, we have developed a modularized surface-enhanced Raman spectroscopy (SERS) labeling strategy, where each Raman reporter is coupled with lysine as a signal-lysine module, and thus the number of Raman reporters can be precisely controlled by the modularized solid-phase peptide synthesis. Using this strategy, we screened out an optimum Raman biosensor for ultrasensitive exosome detection, with the limit of detection of 2.4 particles per microliter. This biosensor enables a successful detection of the tumor with an average diameter of approximately 3.55 mm, and thus enables successful surveillance of the postoperative tumor recurrence in mice models and distinguishing cancer patients from healthy subjects. Our work provides a de novo strategy to precisely amplify signals toward a myriad of biosensor-related medical applications.

Photodegradable CuS SERS Probes for Intraoperative Residual Tumor Detection, Ablation, and Self-Clearance.

Surface-enhanced Raman scattering (SERS) probes have exhibited great potential in biomedical applications. However, currently reported SERS probes are mainly fabricated by nondegradable Au or Ag nanostructures, which are not favorably cleared from the imaged tissues. This bottleneck hinders their in vivo applications. We herein explore a degradable SERS probe consisting of hollow CuS nanoparticles (NPs) to circumvent the current limitation. We identify, for the first time, the Raman enhancement effects of hollow CuS NPs as a SERS probe for Raman imaging of residual tumor lesions. Uniquely, CuS SERS probes are degradable, which stems from laser-induced photothermal effects of CuS NPs, leading to their disintegration from shell structures into individual crystals, thus facilitating their self-clearance from imaged tissues. This novel CuS SERS probe with photodegradation characteristics opens avenues for applying Raman imaging toward a myriad of biomedical applications.

Albumin tailoring fluorescence and photothermal conversion effect of near-infrared-II fluorophore with aggregation-induced emission characteristics.

Fluorophores with donor-acceptor-donor groups with the emission spanning the second near-infrared window (NIR-II) have recently received great attention for biomedical application. Yet, the mechanism underlying the equilibrium between fluorescence (radiative decay) and photothermal effect (non-radiative decay) of these fluorophores remains elusive. Here, we demonstrate that a lipophilic NIR-II fluorophore, BPBBT, possesses both twisted intramolecular charge transfer (TICT) and aggregation-induced emission (AIE) characteristics. Human serum albumin (HSA) binds to BPBBT, which changes the planarity of the fluorophore and restricts its intramolecular rotation. The binding results in alteration to the equilibrium between AIE and TICT state of BPBBT, tailoring its fluorescence and photothermal efficiency. Under the guidance of intraoperative NIR-II fluorescence image, the prepared HSA-bound BPBBT nanoparticles delineate primary orthotopic mouse colon tumor and metastatic lesions with dimensions as small as 0.5 mm × 0.3 mm, and offer photothermal ablation therapy with optimized timing, dosing and area of the laser irradiation.

CuS Nanoparticles as a Photodynamic Nanoswitch for Abrogating Bypass Signaling To Overcome Gefitinib Resistance.

Bypass signaling activation plays a crucial role in the acquired resistance of gefitinib, the first targeted drug in the clinic to treat advanced non-small cell lung cancer. Although the inactivation of bypass signaling by small-molecule inhibitors or monoclonal antibodies may overcome gefitinib resistance, their clinical use has been limited by the complex production process and off-target toxicity. Here we show CuS nanoparticles (NPs) behaved as a photodynamic nanoswitch to specifically abrogate overactive bypass signaling in resistant tumor cells without interfering with the same signal pathways in normal cells. In representative insulin growth factor-1 receptor (IGF1R) bypass activation-induced gefitinib resistant tumors, CuS NPs upon near-infrared laser irradiation locally elevated reactive oxygen species (ROS) level in tumor cells, leading to the blockage of bypass IGF1R and its downstream AKT/ERK/NF-κB signaling cascades. Consequently, laser-irradiated CuS NPs sensitized tumors to gefitinib treatment and prolonged the survival of mice with no obvious toxicity. Laser-irradiated CuS NPs may serve as a simple and safe nanomedicine strategy to overcome bypass activation-induced gefitinib resistance in a specific and controllable manner and provide insights into the treatment of a myriad of other resistant tumors in the field of cancer therapy.

para-Aminothiophenol Radical Reaction-Functionalized Gold Nanoprobe for One-to-All Detection of Five Reactive Oxygen Species In Vivo.

Five major reactive oxygen species (ROS) are generated in diseases including H2O2, •OH, O2•-, ROO•, and 1O2. Simultaneous detection of the five ROS with a single probe is crucial for a comprehensive understanding of the development and progression of many diseases, such as cancer and inflammatory diseases. However, currently reported detection systems are limited by targeting one ROS with one probe. This one-to-one detection mode may fail to sufficiently unveil the diseased state. In this study, we achieved simultaneous detection of all the five ROS with one probe (i.e., one-to-all detection), by designing a novel para-aminothiophenol (PATP) and hemin-decorated gold (Au/PATP/Hemin) nanoprobe. The design is principled by our discovery that PATP can react with •OH, O2•-, ROO•, and 1O2 by a radical oxidative coupling mechanism to form 4,4'-dimercaptoazobenzene (DMAB). The DMAB then elicited strong characteristic surface-enhanced Raman scattering (SERS) peaks at 1142, 1386, and 1432 cm-1; which in turn enables direct detection of •OH, O2•-, ROO•, and 1O2 and indirect detection of H2O2 by hemin-catalyzed fenton reaction to convert H2O2 into •OH. In two representative ROS-elevated mice models of tumors and allergic dermatitis, the Au/PATP/Hemin nanoprobe demonstrated its robust performance of monitoring tumor development and inflammation progression in a highly sensitive and quantitative manner.

Intraoperative Detection and Eradication of Residual Microtumors with Gap-Enhanced Raman Tags.

The inability to intraoperatively diagnose and eliminate microscopic residual tumors represents a significant challenge in cancer surgery. These residual microtumors cause lethal recurrence and metastasis. Herein, we show a crucial example of Raman imaging with gap-enhanced Raman tags (GERTs) to serve as a robust platform for intraoperative detection and eradication of residual microscopic foci, which exist in surgical margins, tumor invasion, and multifocal tumor spread. The GERTs feature gap-enhanced gold core-shell nanostructures, with Raman reporters embedding inside the interior gap junction. This nanostructure elicits highly sensitive and photostable Raman signals for microtumor detection by applying a 785 nm, low-energy laser and produces hyperthermia effects for microtumor ablation upon switching a 808 nm, high-power laser. In the orthotopic prostate metastasis tumor model, systematic delivery of GERTs enabled precise imaging and real-time ablation of macroscopic malignant lesions around the surgical bed without damaging normal tissues. Consequently, the GERTs-based surgery prevented local recurrence and delivered 100% tumor-free survival. These results suggest the efficiency of theranostic GERTs for precise detection and removal of residual miroctumors, broadening the avenues to apply Raman-based imaging for theranostic precision medicine.