Smart Nanoplatform for Visualizing Hydrogen Sulfide and Amplifying Oxidative Stress to Tumor Apoptosis

On-line adapted islands SERS Chip for quantitatively sensing H2S molecules in food spoilage

Surface-enhanced Raman scattering (SERS) has extraordinary potential in detecting hydrogen sulfide (H2S) gas molecules due to its high sensitivity and specificity. However, constructing SERS substrates with strong Raman signal enhancement effects has been a major challenge. In this study, a gold/silver nanostars (Au/Ag NSs) islands chip was developed, leveraging the phenomenon that the SERS enhancement can be significantly improved by patterning plasmonic metals with micro/nanostructures. Compared to the SERS mapping spectrogram of the conventional homogeneous Au/Ag NSs chip, uniform and dense hot spots were formed on the surface of the island chip, which is the key to remarkable enhancement of Raman signal. Both chips were functionalized with 4-mercaptophenylboronic acid (4-MPBA) for the quantitative detection of H2S. The islands chip displays 1.6 folds and 2 orders higher blank Raman signal intensity and a limit of detection (LOD) for H2S than conventional homogeneous SERS chips, respectively. The islands chip is also used for on-line monitoring of spoilage in high-protein foods. The detection ranges for H2S were 2 × 10-8 M - 2 × 10-3 M, with a LOD of 1.9 nM. This sensing strategy provides not only a novel approach for on-ling gaseous hazards detection for food spoilage but also a potential possibility for monitoring gas molecules in the environment.

A Fluorescence-SERS Dual-Mode Nanoprobe for Imaging of HSP90 mRNA and Peroxynitrite in Living Cells

The dysregulation of heat shock protein 90 mRNA (HSP90 mRNA) and reactive oxygen species (ROS) is implicated in stress response and various diseases. Visualizing HSP90 mRNA and ROS dynamics is important to studying their interactions and related physiopathological mechanisms. However, effective methods for detecting both remain lacking. Herein, a covalent organic framework-based (COF-based) dual-mode nanoprobe is designed to monitor HSP90 mRNA and ONOO- (ROS model). The nanoprobe is prepared by in situ assembly of a COF shell as the aptamer carrier on the gold nanorods (AuNRs), followed by conjugation of the ONOO--responsive molecule, 4-mercaptophenylboronic acid (4-MPBA), to the AuNRs and modification of the HSP90 mRNA aptamer (HSP90MB) onto the COF shell. The prepared nanoprobe enables sensitive and selective fluorescence (FL) and surface-enhanced Raman spectroscopy (SERS) detection of HSP90 mRNA and ONOO-, respectively. The dual-channel detection highlights the advantages of facilitating spectral analysis and eliminating mutual interference. In addition, the proposed strategy visualizes a positive interaction between HSP90 mRNA and ONOO- in living cells, revealing their cellular response mechanism under stress conditions and related diseases.

Quantitative detection and cellular imaging of hydrogen sulfide using a SERS probe based on AuAg nanocages

Hydrogen sulfide (H2S), a crucial gasotransmitter, plays an essential regulatory role in various physiological and pathological processes. There is an urgent need to develop sensitive and effective detection methods for intracellular H2S, as abnormal H2S levels are closely related to various diseases such as tumors. Herein, a surface-enhanced Raman scattering (SERS) probe was constructed for quantitative detection and imaging of H2S in living cells. The SERS probe was obtained by using gold silver alloy nanocages (AuAg NCs) with superior plasmonic activity as SERS substrate, followed by modification with Raman signal molecule (4-ethynylaniline), mucin1 aptamer and polyethylene glycol. Upon exposure to H2S, Ag in the SERS probe was rapidly and specifically converted to Ag2S, leading to a remarkable decrease in the SERS intensity of the probe at 2010 cm-1, a spectral region within the cell silent region. The developed SERS probe exhibited outstanding performances, including high sensitivity (with a detection limit as low as 0.36 nM for H2S), remarkable selectivity, excellent stability and minimal cytotoxicity. Notably, this SERS probe had been successfully applied for the detection and imaging of both endogenous and exogenous H2S levels in single living cells without bio-interference, highlighting its potential for precise and accurate intracellular H2S monitoring. This advancement provides a powerful tool for studying H2S-related physiological processes and disorders.

Multifunctional porous organic polymer-based hybrid nanoparticles for sonodynamically enhanced cuproptosis and synergistic tumor therapy

Cuproptosis has gained significant attention among different cell death pathways in cancer therapy, which relies on the excessive accumulation of Cu2+ in mitochondria of tumor cells. Nevertheless, the high levels of glutathione in tumor microenvironment chelates with Cu2+ and thereby reducing its cytotoxicity. In this study, we designed core-shell porous organic polymers (POPs) nanoparticles to deliver and accumulate Cu2+ in tumor cells for enhanced cuproptosis. The porous organic polymers, containing bipyridine structural units, were synthesized on the aminated silica template, followed by the coordination of Cu2+ and the loading of artesunate (ART) as the sonosensitizer, yielding the Cu/ART@Hpy nanoparticles. In the acidic tumor microenvironment, the nanoparticles realized pH-responsive release of Cu2+. Meanwhile, the generation of ROS under ultrasound irradiation depleted intracellular glutathione, leading to the increased intracellular accumulation of Cu2+ for cuproptosis and triggering multiple cell death mechanisms for sonodynamically enhanced tumor therapy. Our study highlights the potential of the porous organic polymer as a platform for cuproptosis and synergistic tumor therapy. STATEMENT OF SIGNIFICANCE: Cuproptosis is induced by the excessive accumulation of Cu²⁺ within the mitochondria of tumor cells. However, the high level of glutathione in the tumor microenvironment can chelate Cu²⁺, thereby reducing the therapeutic efficacy. In this study, we developed the core-shell structured Cu/ART@Hpy nanoparticles for pH-responsive delivery of Cu²⁺. Under ultrasound irradiation, the generated reactive oxygen species deplete intracellular glutathione, enhancing Cu²⁺ accumulation for cuproptosis and activating multiple cell death pathways. The Cu/ART@Hpy nanoparticles enable sonodynamically enhanced cuproptosis, achieving synergistic tumor therapy.

Two-pronged strategy: A mitochondria targeting AIE photosensitizer for hydrogen sulfide detection and type I and type II photodynamic therapy

Multifunctional type-I photosensitizers (PSs) for hydrogen sulfide (H2S) detection and photodynamic therapy (PDT) of hypoxia tumors exhibits attractive curative effect but remains a challenging task. Herein, a mitochondria targeted aggregation-induced emission (AIE) photosensitizer TSPy-SS-P was designed and synthesized, which could be used for H2S detection and simultaneously type I and type II PDT. TSPy-SS-P had excellent selectivity and anti-interference abilities for endogenous and exogenous H2S detection in tumor cells. TSPy-SS-P was able to distinguish tumor cells with high level of H2S from normal cells by fluorescence "turn off" response to H2S. In addition, TSPy-SS-P showed type Ⅰ and type Ⅱ reactive oxygen species (ROS) generation ability to effectively ablate hypoxic tumor cells. TSPy-SS-P showed mitochondria targeting capacity which could produce ROS in situ to disrupt mitochondria and promote cell apoptosis. In vivo PDT experiments showcased that TSPy-SS-P had excellent tumor retention capability, effective tumor ablation ability and good biocompatibility. This work provided a two-pronged strategy to design organelles targeted photosensitizers for H2S detection and effective PDT of tumors.

Reaction-Based SERS Probes for the Detection of Raman-Inactive Species

Surface-enhanced Raman spectroscopy (SERS) has the advantages of high sensitivity, low water interference, narrow spectral peaks for multicomponent analysis, and rich molecular fingerprint information, presenting great potential to be a robust analytical technology. However, a key issue is the unavailability in directly detecting Raman-inactive species with a small Raman scattering cross-section. Current research has addressed this issue by using specific chemical reactions to induce significant characteristic changes in SERS signals, enabling the sensitive and selective detection of Raman-inactive species. This reaction-activated SERS sensing strategy provides a clever approach to the precise determination of Raman-inactive species. In this review, we have first summarized the design principles and types of reaction-based SERS probes. Furthermore, we have examined the enormous potential of reaction-based SERS probes in the detection of bioactive species, environmental pollutants, and food contaminants. Finally, we have discussed in depth the challenges and prospects of reaction-based SERS probes on stability, reliability, and intelligence. The review is aimed to inspire a more advanced design of reaction-based SERS probes, thus further facilitating their extensive applications in SERS analysis.

Cell membrane-targeted surface enhanced Raman scattering nanoprobes for the monitoring of hydrogen sulfide secreted from living cells

Hydrogen sulfide (H2S), an important gas signal molecule, participates in intercellular signal transmission and plays a considerable role in physiology and pathology. However, in-situ monitoring of H2S level during the processes of material transport between cells remains considerably challenging. Herein, a cell membrane-targeted surface-enhanced Raman scattering (SERS) nanoprobe was designed to quantitatively detect H2S secreted from living cells. The nanoprobes were fabricated by assembling cholesterol-functionalized DNA strands and dithiobis(phenylazide) (DTBPA) molecules on core-shell gold nanostars embedded with 4-mercaptoacetonitrile (4-MBN) (AuNPs@4-MBN@Au). Thus, three functions including cell-membrane targeted via cholesterol, internal standard calibration, and responsiveness to H2S through reduction of azide group in DTBPA molecules were integrated into the nanoprobes. In addition, the nanoprobes can quickly respond to H2S within 90 s and sensitively, selectively, and reliably detect H2S with a limit of detection as low as 37 nM due to internal standard-assisted calibration and reaction specificity. Moreover, the nanoprobes can effectively target on cell membrane and realize SERS visualization of dynamic H2S released from HeLa cells. By employing the proposed approach, an intriguing phenomenon was observed: the other two major endogenous gas transmitters, carbon monoxide (CO) and nitric oxide (NO), exhibited opposite effect on H2S production in living cells stimulated by related gas release molecules. In particular, the introduction of CO inhibited the generation of H2S in HeLa cells, while NO promoted its output. Thus, the nanoprobes can provide a robust method for investigating H2S-related extracellular metabolism and intercellular signaling transmission.