Indocyanine green-loaded gold nanostars for sensitive SERS imaging and subcellular monitoring of photothermal therapy

Au@CuS Nanoshells for Surface-Enhanced Raman Scattering Image-Guided Tumor Photothermal Therapy with Accelerated Hepatobiliary Excretion

Gold-based nanoparticles for surface-enhanced Raman scattering (SERS) imaging show great potential for precise tumor detection and photothermal therapy (PTT). However, the metabolizability of gold nanoparticles (Au NPs) raises big concerns. Herein, we designed a core-shelled nanostructure of copper sulfide (CuS)-coated Au NPs with surface pegylation (PEG-Au@CuS NSs). The excreted Au in the gallbladders at 1 h and 4 h in mice injected with PEG-Au@CuS NSs was 8.2- and 19.1-fold of that with the pegylated Au NPs (PEG-AuNPs) of the same Au particle size, respectively. By loading the Raman reporter 3,3'-Diethylthiatricarbocyanine iodide (DTTC) in the core-shell junction of PEG-Au@CuS NSs, the PEG-Au-DTTC@CuS NSs exhibited the Raman signal-to-noise (S/N) ratio of 4.01 after 24 h of intravenous (IV) injection in the mice bearing an orthotopic CT26-Luc colon tumor. By contrast, the DTTC-coated PEG-AuNPs (PEG-Au-DTTC NPs) achieved an S/N ratio of 2.71. Moreover, PEG-Au-DTTC@CuS NSs exhibited an increased photothermal conversion effect compared with PEG-Au-DTTC NPs excited with an 808-nm laser. PEG-Au-DTTC@CuS NSs enabled intraoperative SERS image-guided photothermal therapy for a complete cure of the colon tumor-bearing mice. Our data demonstrated that the PEG-Au-DTTC@CuS NSs are promising intraoperative Raman image-guided theranostic nanoplatform with enhanced hepatobiliary excretion.

Structural engineering of mitochondria-targeted Au-Ag2S photosensitizers for enhanced photodynamic and photothermal therapy

Much effort has been devoted to designing diverse photosensitizers for efficient photodynamic therapy (PDT) and photothermal therapy (PTT) performance. However, the effect of PS morphology on the PDT and PTT performance needs to be further explored. In this work, a photosensitizer, Au-Ag2S nanoparticles functionalized with indocyanine green, caspase-3 recognition peptides, and mitochondria-targeting peptides (AICM NPs) with different morphologies, including core-shell, eccentric core-shell-I, eccentric core-shell-II, and Janus morphologies, were synthesized to enhance PDT and PTT performance. Among them, AICM Janus NPs with enhanced charge-transfer efficiency and photothermal conversion demonstrate superior PDT and PTT performance compared to those of other morphologies. In addition, AICM NPs exhibit satisfactory surface-enhanced Raman scattering performance for in situ SERS monitoring of caspase-3 during PDT and PTT processes. After PDT and PTT treatment with AICM Janus NPs, the damaged mitochondria released caspase-3. AICM Janus NPs achieved a superior apoptosis rate in tumor cells in vitro. Furthermore, AICM Janus NPs treat the tumors in vivo within only 10 days, which is half the time reported in other work. The AICM NPs demonstrated superior therapeutic safety both in vitro and in vivo. This study investigates the effects of morphology-property-performance of photosensitizers on the PDT and PTT performances, which opens a new pathway toward designing photosensitizers for efficient PDT and PTT.

Nanoparticle-mediated thermal Cancer therapies: Strategies to improve clinical translatability

Despite significant advances, cancer remains a leading global cause of death. Current therapies often fail due to incomplete tumor removal and nonspecific targeting, spurring interest in alternative treatments. Hyperthermia, which uses elevated temperatures to kill cancer cells or boost their sensitivity to radio/chemotherapy, has emerged as a promising alternative. Recent advancements employ nanoparticles (NPs) as heat mediators for selective cancer cell destruction, minimizing damage to healthy tissues. This approach, known as NP hyperthermia, falls into two categories: photothermal therapies (PTT) and magnetothermal therapies (MTT). PTT utilizes NPs that convert light to heat, while MTT uses magnetic NPs activated by alternating magnetic fields (AMF), both achieving localized tumor damage. These methods offer advantages like precise targeting, minimal invasiveness, and reduced systemic toxicity. However, the efficacy of NP hyperthermia depends on many factors, in particular, the NP properties, the tumor microenvironment (TME), and TME-NP interactions. Optimizing this treatment requires accurate heat monitoring strategies, such as nanothermometry and biologically relevant screening models that can better mimic the physiological features of the tumor in the human body. This review explores the state-of-the-art in NP-mediated cancer hyperthermia, discussing available nanomaterials, their strengths and weaknesses, characterization methods, and future directions. Our particular focus lies in preclinical NP screening techniques, providing an updated perspective on their efficacy and relevance in the journey towards clinical trials.

Graphene-wrapped petal-like gap-enhanced Raman tags for enhancing photothermal conversion and Raman imaging

Multifunctional nanoplatform that combine imaging, diagnostic, and therapeutic functions into a single agent have great significance for the early diagnosis and efficient treatment of diseases, particularly tumors. In this study, we report on a novel graphene-wrapped petal-like gap-enhanced Raman tags with mesoporous silica shells (MS-GP-GERTs). These MS-GP-GERTs have 4-NBT Raman reporters embedded in the gap between the gold nanocore and the petal-shaped shell and are wrapped in graphene and mesoporous silica. The results of photothermal measurement experiments show that graphene layers significantly enhanced the photothermal effect of gap-enhanced Raman tags (GERTs). The photothermal conversion efficiency of MS-GP-GERTs reaches 40.8%, comparable to pure graphene. Moreover, MS-GP-GERTs show good photothermal performance in agarose phantoms, heating the phantom to 47 °C within 5 min under a low power density laser (0.5 W/cm2). MS-GP-GERTs also exhibit excellent photothermal stability and physiological environment stability, making them a promising candidate for repeated photothermal therapy. Raman spectra and mapping imaging experiments demonstrate MS-GP-GERTs' low detection limit (100 fM), large imaging depth (2.74 mm), and excellent ability to image simulated biological tissue and cells. This novel Raman tag has the potential to become a multifunctional nano platform for integrating Raman imaging diagnosis and photothermal therapy.

Use of Albumin for Drug Delivery as a Diagnostic and Therapeutic Tool

Drug delivery is an important topic that has attracted the attention of researchers in recent years. Albumin nanoparticles play a significant role in drug delivery as a carrier due to their unique characteristics. Albumin is non-toxic, biocompatible, and biodegradable. Its structure is such that it can interact with different drugs, which makes the treatment of the disease faster and also reduces the side effects of the drug. Albumin nanoparticles can be used in the diagnosis and treatment of many diseases, including cancer, diabetes, Alzheimer's, etc. These nanoparticles can connect to some compounds, such as metal nanoparticles, antibodies, folate, etc. and create a powerful nanostructure for drug delivery. In this paper, we aim to investigate albumin nanoparticles in carrier format for drug delivery application. In the beginning, different types of albumin and their preparation methods were discussed, and then albumin nanoparticles were discussed in detail in diagnosing and treating various diseases.

Challenges and advances for glioma therapy based on inorganic nanoparticles

Glioma is one of the most serious central nervous system diseases, with high mortality and poor prognosis. Despite the continuous development of existing treatment methods, the median survival time of glioma patients is still only 15 months. The main treatment difficulties are the invasive growth of glioma and the obstruction of the blood-brain barrier (BBB) to drugs. With rapid advancements in nanotechnology, inorganic nanoparticles (INPs) have shown favourable application prospects in the diagnosis and treatment of glioma. Due to their extraordinary intrinsic features, INPs can be easily fabricated, while doping with other elements and surface modification by biological ligands can be used to enhance BBB penetration, targeted delivery and biocompatibility. Guided glioma theranostics with INPs can improve and enhance the efficacy of traditional methods such as chemotherapy, radiotherapy and gene therapy. New strategies, such as immunotherapy, photothermal and photodynamic therapy, magnetic hyperthermia therapy, and multifunctional inorganic nanoplatforms, have also been facilitated by INPs. This review emphasizes the current state of research and clinical applications of INPs, including glioma targeting and BBB penetration enhancement methods, in vivo and in vitro biocompatibility, and diagnostic and treatment strategies. As such, it provides insights for the development of novel glioma treatment strategies.

Nanomaterials meet surface-enhanced Raman scattering towards enhanced clinical diagnosis: a review

Surface-enhanced Raman scattering (SERS) is a very promising tool for the direct detection of biomarkers for the diagnosis of i.e., cancer and pathogens. Yet, current SERS strategies are hampered by non-specific interactions with co-existing substances in the biological matrices and the difficulties of obtaining molecular fingerprint information from the complex vibrational spectrum. Raman signal enhancement is necessary, along with convenient surface modification and machine-based learning to address the former issues. This review aims to describe recent advances and prospects in SERS-based approaches for cancer and pathogens diagnosis. First, direct SERS strategies for key biomarker sensing, including the use of substrates such as plasmonic, semiconductor structures, and 3D order nanostructures for signal enhancement will be discussed. Secondly, we will illustrate recent advances for indirect diagnosis using active nanomaterials, Raman reporters, and specific capture elements as SERS tags. Thirdly, critical challenges for translating the potential of the SERS sensing techniques into clinical applications via machine learning and portable instrumentation will be described. The unique nature and integrated sensing capabilities of SERS provide great promise for early cancer diagnosis or fast pathogens detection, reducing sanitary costs but most importantly allowing disease prevention and decreasing mortality rates.

Nanotechnology-Based Combinatorial Anti-Glioblastoma Therapies: Moving from Terminal to Treatable

Aggressive glioblastoma (GBM) has no known treatment as a primary brain tumor. Since the cancer is so heterogeneous, an immunosuppressive tumor microenvironment (TME) exists, and the blood–brain barrier (BBB) prevents chemotherapeutic chemicals from reaching the central nervous system (CNS), therapeutic success for GBM has been restricted. Drug delivery based on nanocarriers and nanotechnology has the potential to be a handy tool in the continuing effort to combat the challenges of treating GBM. There are various new therapies being tested to extend survival time. Maximizing therapeutic effectiveness necessitates using many treatment modalities at once. In the fight against GBM, combination treatments outperform individual ones. Combination therapies may be enhanced by using nanotechnology-based delivery techniques. Nano-chemotherapy, nano-chemotherapy–radiation, nano-chemotherapy–phototherapy, and nano-chemotherapy–immunotherapy for GBM are the focus of the current review to shed light on the current status of innovative designs.

Micro-Opening Ridged Waveguide Tumor Hyperthermia Antenna Combined with Microwave-Sensitive MOF Material for Tumor Microwave Hyperthermia Therapy

Microwave hyperthermia is an emerging minimally invasive therapy in which thermal damage and apoptosis of tumor cells are induced by local heating of tissues with microwave radiation. Recently, microwave hyperthermia has been widely used in clinical practice; however, uneven aggregation and dispersion of malignant tumors after microwave hyperthermia are the main problems associated with this method. In this work, a microridged waveguide tumor hyperthermia antenna with an operating frequency of 915 MHz was designed. Although its volume is only 6.6 cm3, it exhibited a highly focused heating effect, achieving rapid heating in a small area. However, microwave hyperthermia has several shortcomings. Microwaves cannot specifically identify and target tumors; this decreases the efficiency of the treatment if the temperature of the tumor site is not sufficiently high for its size and location. Therefore, Zr metal-organic framework (ZrMOF)-derived composite ZCNC was synthesized using the ultrasonic aerosol flow method, which has good microwave sensitization and biosafety. ZCNC reduced the damage to normal cells and greatly improved the tumor treatment effect of microwave hyperthermia (tumor inhibition rate reached 78.01%). Thus, the proposed strategy effectively improves the current clinical microwave hyperthermia treatment method.

Recent Advances in Agglomeration Detection and Dual-Function Application of Surface-Enhanced Raman Scattering (SERS)

Surface-enhanced Raman scattering (SERS) has been widely utilized in early detection of disease biomarkers, cell imaging, and trace contamination detection, owing to its ultra-high sensitivity. However, it is also subject to certain application restrictions in virtue of its expensive detection equipment and long-term stability of SERS-active substrate. Recently, great progress has been made in SERS technology, represented by agglomeration method. Dual readout signal detection methods are combined with SERS, including electrochemical detection, fluorescence detection, etc., establishing a new fantastic viewpoint for application of SERS. In this review, we have made a comprehensive report on development of agglomeration detection and dual-function detection methods based on SERS. The synthesis methods for plasmonic materials and mainstream SERS enhancement mechanism are also summarized. Finally, the key facing challenges are discussed and prospects are addressed.

Tri-functional SERS nanoplatform with tunable plasmonic property for synergistic antibacterial activity and antibacterial process monitoring

Strategies integrating synergistic high-efficiency bacterial killing and antibacterial process monitoring capability are desirable. Herein, a tri-functional surface-enhanced Raman spectroscopy (SERS) nanoplatform, namely 4-mercaptobenzoic acid-encoded gold nanorods@silver coated with a layer of bovine serum albumin (AuNRs@Ag@4-MBA@BSA), with excellent biocompatibility, stability, tunable plasmonic property and activatable photothermal effect is introduced for Ag⁺/photothermal therapy (PTT) synergistic antibacterial activity and antibacterial process monitoring. An exogenous etchant is used to controllably model the physiological process of metallic silver biodegradation. Ag shell etching causes the surface plasmon resonance band of SERS nanotags to red-shift to near-infrared region, activates the photothermal conversion capability, and triggers PTT, which in turn accelerates Ag shell etching. The antibacterial rates for Staphylococcus aureus and Escherichia coli after 10 min treatment can achieve 99.5% and 99.9%, respectively. Furthermore, the near-field effect and ultrasensitive property render the SERS intensity decrease ratio is dependent on Ag shell etching as well as temperature rising and thus relevant to antibacterial activity. We have demonstrated a strong correlation between SERS signal and antibacterial effect, and have verified the possibility of antibacterial process monitoring in vitro using SERS-based methodology. We envision that our integrated strategy being used for in vivo high-efficiency bacterial killing and antibacterial process monitoring.

Visible-light and near-infrared fluorescence and surface-enhanced Raman scattering point-of-care sensing and bio-imaging: a review

This review article deals with the concepts, principles and applications of visible-light and near-infrared (NIR) fluorescence and surface-enhanced Raman scattering (SERS) in in vitro point-of-care testing (POCT) and in vivo bio-imaging. It has discussed how to utilize the biological transparency windows to improve the penetration depth and signal-to-noise ratio, and how to use surface plasmon resonance (SPR) to amplify fluorescence and SERS signals. This article has highlighted some plasmonic fluorescence and SERS probes. It has also reviewed the design strategies of fluorescent and SERS sensors in the detection of metal ions, small molecules, proteins and nucleic acids. Particularly, it has provided perspectives on the integration of fluorescent and SERS sensors into microfluidic chips as lab-on-chips to realize point-of-care testing. It has also discussed the design of active microfluidic devices and non-paper- or paper-based lateral flow assays for in vitro diagnostics. In addition, this article has discussed the strategies to design in vivo NIR fluorescence and SERS bio-imaging platforms for monitoring physiological processes and disease progression in live cells and tissues. Moreover, it has highlighted the applications of POCT and bio-imaging in testing toxins, heavy metals, illicit drugs, cancers, traumatic brain injuries, and infectious diseases such as COVID-19, influenza, HIV and sepsis.

Near-Infrared Light-Responsive SERS Tags Enable Positioning and Monitoring of the Drug Release of Photothermal Nanomedicines In Vivo

Understanding the in vivo behavior of photothermal nanomedicines (PTNMs) is important for drug development and evaluation. However, it is still very challenging. Herein, two key parameters, i.e., the depth of PTNMs under biological tissue and the drug release ratio of PTNMs in vivo, can be revealed by a near-infrared (NIR) light-responsive surface-enhanced Raman scattering (SERS) strategy. The fabricated PTNMs were composed of waxberry-like gold nanoparticles, model drug curcumin, and an elaborately selected NIR light-responsive Raman reporter (3,3'-diethylthiatricarbocyanine iodide, DTTC). The response mechanism of DTTC to NIR light was investigated as photodegradation. NIR light irradiation heated the gold nanoparticles, triggered the release of a model drug, and simultaneously decreased the SERS intensity of the PTNMs. In vitro experiment results revealed that the SERS intensity decrease could well reflect the depth of PTNMs with a correlation coefficient of more than 0.99. On this basis, after in situ SERS detection, the depth of PTNMs in a tumor could be revealed with satisfactory accuracy. Moreover, the decrease in the SERS intensity of PTNMs showed a highly similar trend to the increase in the drug release, suggesting that it could be used for real-time monitoring of drug release of PTNMs. This study not only opens a new avenue for the release study of many inactive fluorescent and Raman drugs of PTNMs but also provides an effective way for reporting the depth, which greatly promotes the application of PTNMs in vivo.

Probing the Intracellular Bio-Nano Interface in Different Cell Lines with Gold Nanostars

Gold nanostars are a versatile plasmonic nanomaterial with many applications in bioanalysis. Their interactions with animal cells of three different cell lines are studied here at the molecular and ultrastructural level at an early stage of endolysosomal processing. Using the gold nanostars themselves as substrate for surface-enhanced Raman scattering, their protein corona and the molecules in the endolysosomal environment were characterized. Localization, morphology, and size of the nanostar aggregates in the endolysosomal compartment of the cells were probed by cryo soft-X-ray nanotomography. The processing of the nanostars by macrophages of cell line J774 differed greatly from that in the fibroblast cell line 3T3 and in the epithelial cell line HCT-116, and the structure and composition of the biomolecular corona was found to resemble that of spherical gold nanoparticles in the same cells. Data obtained with gold nanostars of varied morphology indicate that the biomolecular interactions at the surface in vivo are influenced by the spike length, with increased interaction with hydrophobic groups of proteins and lipids for longer spike lengths, and independent of the cell line. The results will support optimized nanostar synthesis and delivery for sensing, imaging, and theranostics.

Development of a multi-functional preclinical device for the treatment of glioblastoma

Glioblastoma multiforme (GBM) is one of the most common and aggressive malignant primary brain tumors in adults. The treatment of GBM is limited by the blood-brain barrier (BBB), which limits the diffusion of appropriate concentrations of therapeutic agents at the tumor site. Among experimental therapies, photo-thermal therapy (PTT) mediated by nanoparticles is a promising strategy. To propose a preclinical versatile research instrument for the development of new PTT for GBM, a multipurpose integrated preclinical device was developed. The setup is able to perform: i) BBB permeabilization by focused ultrasound sonication (FUS); ii) PTT with continuous wave laser; iii) in situ temperature monitoring with photo-acoustic (PA) measurements. In vivo preliminary subcutaneous and transcranial experiments were conducted on healthy or tumor-bearing mice. Transcranial FUS-induced BBB permeabilization was validated using single photon emission computed tomography (SPECT) imaging. PTT capacities were monitored by PA thermometry, and are illustrated through subcutaneous and transcranial in vivo experiments. The results show the therapeutic possibilities and ergonomy of such integrated device as a tool for the validation of future treatments.

Single-chain antibody-decorated Au nanocages@liposomal layer nanoprobes for targeted SERS imaging and remote-controlled photothermal therapy of melanoma cancer cells

The development of theranostic platforms combining surface-enhanced Raman spectroscopy (SERS) imaging with NIR-stimulated photothermal therapy (PTT) is of utmost importance for the precise diagnosis and selective treatment of cancers, especially in superficial solid tumors. For this purpose, a versatile theranostic nanoprobe of liposomal layer-coated Au nanocages (AuNCs) was decorated with an anti-MUC18 single-chain antibody (scFv). 4-mercapto benzoic acid (p-MBA)-labeled AuNCs (p-AuNCs) were coated by a liposomal layer (p-AuNCs@lip), followed by conjugating anti-MUC18 scFv via post-insertion method to form immuno-liposomal layer-coated AuNCs (p-AuNCs@scFv-lip). Physicochemical characterizations of the p-AuNCs@scFv-lip were investigated by transmission electron microscopy (TEM) and UV-vis and Raman spectroscopy. Furthermore, the targeting ability and theranostic efficiency of the nanoprobe were evaluated for specific diagnosis and treatment of cancerous melanoma cells by flow cytometry, SERS mapping, and live/dead assay. The formation of lipid layer on p-AuNCs surface was confirmed by TEM imaging. After decorating the liposomal layer with scFv, a relevant red shift was observed in the UV-vis spectrum. Moreover, p-AuNCs@lip presented characteristic peaks in the Raman spectrum, which exhibited only a minor change after scFv conjugation (p-AuNCs@scFv-lip). Interestingly, the cellular uptake of AuNCs@scFv-lip by A375 cell line (MUC18⁺) showed a 24-fold enhancement compared with SKBR3 cells (MUC18^-). AuNCs@scFv-lip specifically identified A375 cells from SKBR cells via SERS mapping and effectively killed A375 cells through the PTT mechanism. Taken together, this theranostic platform can provide a promising tool for both in situ diagnosis and remote-controlled thermal ablation of cancer cells.

Camouflaged Gold Nanodendrites Enable Synergistic Photodynamic Therapy and NIR Biowindow II Photothermal Therapy and Multimodal Imaging

Gold nanodendrite (AuND)-based nanotheranostic agents with versatile capabilities were fabricated by optimizing the geometrical configurations (dendrite length and density) of AuND to achieve localized surface plasmon resonance (LSPR) in near-infrared biowindow II (NIR-II), and then subsequently functionalizing with a mitochondria-targeting compound (triphenylphosphonium, TPP), loading with an NIR-photosensitizer (indocyanine green, ICG) and coating with the macrophage cell membrane (MCM) to trap ICG within AuND and selectively interact with MDA-MB-231 cells. The novel AuND-TPP-ICG@MCM system enabled the integration of multimodal fluorescence/photoacoustic/surface-enhanced Raman imaging with synergistic therapies of NIR-II photothermal therapy and NIR-I photodynamic therapy for cancer treatment. Enhanced hyperthermia and elevated production of reactive oxygen species within the tumors via MCM coating and mitochondria targeting afforded a synergistic efficacy for tumor eradication with limited side effects. The demonstrated biocompatibility, multi-imaging capability, and high therapeutic efficiency under NIR laser irradiation indicate the potentials of this multifunctional nanotheranostic platform for clinical utility in cancer therapy.

Photothermal Therapy for the Treatment of Glioblastoma: Potential and Preclinical Challenges

Glioblastoma (GBM) is a very aggressive primary malignant brain tumor and finding effective therapies is a pharmaceutical challenge and an unmet medical need. Photothermal therapy may be a promising strategy for the treatment of GBM, as it allows the destruction of the tumor using heat as a non-chemical treatment for disease bypassing the GBM heterogeneity limitations, conventional drug resistance mechanisms and side effects on peripheral healthy tissues. However, its development is hampered by the distinctive features of this tumor. Photoabsorbing agents such as nanoparticles need to reach the tumor site at therapeutic concentrations, crossing the blood-brain barrier upon systemic administration. Subsequently, a near infrared light irradiating the head must cross multiple barriers to reach the tumor site without causing any local damage. Its power intensity needs to be within the safety limit and its penetration depth should be sufficient to induce deep and localized hyperthermia and achieve tumor destruction. To properly monitor the therapy, imaging techniques that can accurately measure the increase in temperature within the brain must be used. In this review, we report and discuss recent advances in nanoparticle-mediated plasmonic photothermal therapy for GBM treatment and discuss the preclinical challenges commonly faced by researchers to develop and test such systems.

Intracellular optical probing with gold nanostars

Gold nanostars are important nanoscopic tools in biophotonics and theranostics. To understand the fate of such nanostructures in the endolysosomal system of living cells as an important processing route in biotechnological approaches, un-labelled, non-targeted gold nanostars synthesized using HEPES buffer were studied in two cell lines. The uptake of the gold nanostructures leads to cell line-dependent intra-endolysosomal agglomeration, which results in a greater enhancement of the local optical fields than those around individual nanostars and near aggregates of spherical gold nanoparticles of the same size. As demonstrated by non-resonant surface-enhanced Raman scattering (SERS) spectra in the presence and absence of aggregation, the spectroscopic signals of molecules are of very similar strength over a wide range of concentrations, which is ideal for label-free vibrational characterization of cells and other complex environments. In 3T3 and HCT-116 cells, SERS data were analyzed together with the properties of the intracellular nanostar agglomerates. Vibrational spectra indicate that the processing of nanostars by cells and their interaction with the surrounding endolysosomal compartment is connected to their morphological properties through differences in the structure and interactions in their intracellular protein corona. Specifically, different intracellular processing was found to result from a different extent of hydrophobic interactions at the pristine gold surface, which varies for nanostars of different spike lengths. The sensitive optical monitoring of surroundings of nanostars and their intracellular processing makes them a very useful tool for optical bionanosensing and therapy.

Lysosome-Targeted Gold Nanotheranostics for In Situ SERS Monitoring pH and Multimodal Imaging-Guided Phototherapy

The integration of surface-enhanced Raman spectrum (SERS) and fluorescence-photoacoustic multimodal imaging in near-infrared photothermal therapy is highly desirable for cancer theranostic. However, typically, gold nanotheranostics usually require an additional modification of fluorophores and complex design refinements. In this work, by integrating surface-modified cysteine-hydroxyl merocyanine (CyHMC) molecules onto AuNRs, a novel lysosome-targeted gold-based nanotheranostics AuNRs-CyHMC that combines the specificity of Raman spectrum, the speed of fluorescence imaging, and deep penetration of photoacoustic imaging was successfully fabricated. Interestingly, fluorescence and Raman signals in this AuNRs-CyHMC system do not interfere, but it has pH-sensitive Raman signals and self-fluorescence localization ability under different excitation wavelengths. Fluorescence co-localization experiments further confirmed the lysosome-targeting ability of AuNRs-CyHMC. Typically, the proposed nanotheranostics were capable of SERS monitoring pH changes in both phosphate-buffered saline and living cells. Meanwhile, in vitro and in vivo experiments revealed that AuNRs-CyHMC possessed excellent fluorescence-photoacoustic performance and could be used for multimodal imaging-guided photothermal therapy. Furthermore, our work implied that gold nanotheranostics can provide great potential for cancer diagnosis and treatment.

Hypoxia-Responsive Lipid-Polymer Nanoparticle-Combined Imaging-Guided Surgery and Multitherapy Strategies for Glioma

Glioma is the most prevalent type of malignant brain tumor and is usually very aggressive. Because of the high invasiveness and aggressive proliferative growth of glioma, it is difficult to resect completely or cure with surgery. Residual glioma cells are a primary cause of postoperative recurrence. Herein, we describe a hypoxia-responsive lipid polymer nanoparticle (LN) for fluorescence-guided surgery, chemotherapy, photodynamic therapy (PDT), and photothermal therapy (PTT) combination multitherapy strategies targeting glioma. The hypoxia-responsive LN [LN (DOX + ICG)] contains a hypoxia-responsive component poly(nitroimidazole)₂₅ [P-(Nis)₂₅], the glioma-targeting peptide angiopep-2 (A2), indocyanine green (ICG), and doxorubicin (DOX). LN (DOX + ICG) comprises four distinct functional components: (1) A2: A2 modified nanoparticles effectively target gliomas, enhancing drug concentration in gliomas; (2) P-(Nis)₂₅: (i) the hydrophobic component of LN (DOX + ICG) with hypoxia responsive ability to encapsulate DOX and ICG; (ii) allows rapid release of DOX from LN (DOX + ICG) after 808 nm laser irradiation; (3) ICG: (i) ICG allows imaging-guided surgery, combining PDT and PTT therapies; (ii) upon irradiation with an 808 nm laser, ICG creates a hypoxic environment; (4) DOX inhibits glioma growth. This work demonstrates that LN (DOX + ICG) might provide a novel clinical approach to preventing post-surgical recurrence of glioma.

Silica-Coated, Waxberry-like Surface-Enhanced Raman Resonant Scattering Tag-Pair with Near-Infrared Raman Dye Encoding: Toward In Vivo Duplexing Detection

Surface-enhanced Raman resonant scattering (SERRS) tags encoded with near-infrared (NIR) Raman reporters showed great potential for in vivo detection owing to their ultrasensitivity. However, in vivo signal stability of such tags is a remaining problem due to the lack of suitable silica coating method because the weakly adsorbed NIR reporters tend to detach from traditional gold nanosubstrates in the ethanol-rich and high pH conditions, which are commonly used for silica coating. Herein, we propose a silica coating method for NIR SERRS tags by using waxberry-like gold nanoparticles (NPs) as substrates. The lipid bilayer of the NPs played a crucial role in the coating, which can encapsulate the NIR Raman reporter via hydrophobic interactions and prevent the interference from a harsh medium. Thus, the silica-coated tags well preserved ultrasensitivity of bare tags and simultaneously gained satisfactory signal stability in vivo. Moreover, the coating method is compatible for the encapsulation of a variety of thiol group-free NIR reporters (as exemplified by DTTC, Cy7, IR792, and DIR), relying on which a tag-pair with distinguishable peaks can be screened (labeling with DTTC and Cy7, respectively). In vivo duplexing detection revealed that the tag-pair-labeled liposome was cleared faster in the liver than polydopamine NPs within one mouse. The developed method paves an easy way for gaining high-quality SERRS tags and will promote their in vivo multiplex analysis and diagnostics applications.

Ratiometric fluorescence nanoprobe for monitoring of intracellular temperature and tyrosine based on a dual emissive carbon dots/gold nanohybrid

A novel dual-emission nitrogen doped carbon dots/gold nanohybrid (NCDs-Au) was designed for specific and sensitive ratiometric detection of intracellular temperature and tyrosine. In this probe, a reductive NCDs was successfully prepared with the use of natural biomass Dendrobium officinale as precursor. The new prepared NCDs acted as both reducers and stabilizers to synthesize a novel NCDs-Au nanohybrid by a facile one-step procedure along with a quantum yield of 14.3%. The prepared nanoprobe showed characteristic fluorescence emissions of NCDs and Au NCs with single-wavelength excitation. Notably, the nanoprobe shows an interesting wavelength-dependent dual response to temperature (448 nm) and tyrosine (660 nm), enabling the two targets to be detected proportionally. As an effective temperature sensor, the nanoprobe exhibited good temperature-dependent fluorescence with a sensational linear response from 5 to 75 °C. In addition, the sensor has a linear response toward tyrosine in the range of 0.5-175 μM with a detection limit of 0.19 μM. Moreover, the fluorescent nanoprobe was successfully applied to ratiometricly monitor the variation of temperature or tyrosine level in cells because of the low cytotoxicity, chemical stability and excellent fluorescence properties. These results suggested that the nanoprobe here has provided the possibility for rapidly biosensing with the acceptable selectivity and sensitivity.

Metal Nanoparticles-Enhanced Biosensors: Synthesis, Design and Applications in Fluorescence Enhancement and Surface-enhanced Raman Scattering

Metal nanoparticles (NP) that exhibit localized surface plasmon resonance play an important role in metal-enhanced fluorescence (MEF) and surface-enhanced Raman scattering (SERS). Among the optical biosensors, MEF and SERS stand out to be the most sensitive techniques to detect a wide range of analytes from ions, biomolecules to macromolecules and microorganisms. Particularly, anisotropic metal NPs with strongly enhanced electric field at their sharp corners/edges under a wide range of excitation wavelengths are highly suitable for developing the ultrasensitive plasmon-enhanced biosensors. In this review, we first highlight the reliable methods for the synthesis of anisotropic gold NPs and silver NPs in high yield, as well as their alloys and composites with good control of size and shape. It is followed by the discussion of different sensing mechanisms and recent advances in the MEF and SERS biosensor designs. This includes the review of surface functionalization, bioconjugation and (directed/self) assembly methods as well as the selection/screening of specific biorecognition elements such as aptamers or antibodies for the highly selective bio-detection. The right combinations of metal nanoparticles, biorecognition element and assay design will lead to the successful development of MEF and SERS biosensors targeting different analytes both in-vitro and in-vivo. Finally, the prospects and challenges of metal-enhanced biosensors for future nanomedicine in achieving ultrasensitive and fast medical diagnostics, high-throughput drug discovery as well as effective and reliable theranostic treatment are discussed.

Strategies to improve the photothermal capacity of gold-based nanomedicines

The plasmonic photothermal properties of gold nanoparticles have been widely explored in the biomedical field to mediate a photothermal effect in response to the irradiation with an external light source. Particularly, in cancer therapy, the physicochemical properties of gold-based nanomaterials allow them to efficiently accumulate in the tumor tissue and then mediate the light-triggered thermal destruction of cancer cells with high spatial-temporal control. Nevertheless, the gold nanomaterials can be produced with different shapes, sizes, and organizations such as nanospheres, nanorods, nanocages, nanoshells, and nanoclusters. These gold nanostructures will present different plasmonic photothermal properties that can impact cancer thermal ablation. This review analyses the application of gold-based nanomaterials in cancer photothermal therapy, emphasizing the main parameters that affect its light-to-heat conversion efficiency and consequently the photothermal potential. The different shapes/organizations (clusters, shells, rods, stars, cages) of gold nanomaterials and the parameters that can be fine-tuned to improve the photothermal capacity are presented. Moreover, the gold nanostructures combination with other materials (e.g. silica, graphene, and iron oxide) or small molecules (e.g. indocyanine green and IR780) to improve the nanomaterials photothermal capacity is also overviewed.

Oxygen vacancy-enhanced photothermal performance and reactive oxygen species generation for synergistic tumour therapy

Vacancy engineering is a robust strategy to tune nanomaterials' electronic structures for physicochemical properties regulation. Here, we report and realize the first oxygen vacancy-enhanced photothermal and oxidation dual-induced synergistic tumour therapy using oxygen vacancies enriched MnO₂@Au nanoconstructs as the therapeutic agent with a high photothermal effect, enhanced highly-toxic superoxide radical generation, good biocompatibility and tumour microenvironment regulation capacity. Our work opens up a new route for cancer nanotheranostics by regulating the electronic structure of nanomaterials resulting in enhanced efficacy.

Improved SERS activity of non-stoichiometric copper sulfide nanostructures related to charge-transfer resonance

The low enhancement factor of semiconductor SERS substrates is a major obstacle for their practical application. Therefore, there is a need to explore the facile synthesis of new SERS substrates and reveal the SERS enhancement mechanism. Here, we develop a simple, facile and low-cost two-step method to synthesize copper sulfide based nanostructures with different Cu_7.2S₄ contents. The as-synthesized sample is composed of nanosheets with the CuS phase structure. With the increase of the annealing temperature to 300 °C, the CuS content gradually decreases and disappears, and the content of Cu_7.2S₄ and CuSO₄ appears and gradually increases. At the annealing temperature of 350 °C, only CuSO₄ exists. Compared with pure CuS or pure CuSO₄, the detection limit of R6G molecules is the lowest for the composite sample with a higher content of Cu_7.2S₄, indicating that the introduction of non-stoichiometric Cu_7.2S₄ can improve the SERS performance and the higher content of Cu_7.2S₄ leads to a higher SERS activity. Furthermore, to investigate the SERS mechanism, the energy band structures and energy-level diagrams of different probe molecules over CuS, Cu_7.2S₄ and Cu_xS are studied by DFT calculations. Theoretical calculations indicate that the excellent SERS behavior depends on charge transfer resonance. Our work provides a general approach for the construction of excellent metal compound semiconductor SERS active substrates.

Mutual impact of clinically translatable near-infrared dyes on photoacoustic image contrast and in vitro photodynamic therapy efficacy

Photodynamic therapy (PDT), a spatially localized phototoxic therapy that involves irradiation of a photosensitizer (PS) with specific wavelengths of light, has shown exceptional promise in impacting cancer treatment outcomes, particularly oral cancer. To reduce PDT outcome variability, attempts toward image-guided personalized PDT are being pursued by monitoring PS uptake either via fluorescence or photoacoustic imaging (PAI), a nonionizing modality dependent on optical absorption properties of the tissue. PAI-guided PDT requires a near-infrared contrast agent for deep tissue imaging with minimal photobleaching effect. We evaluate the impact of PDT agent, benzoporphyrin derivative (BPD), on PAI agent indocyanine green (ICG) and vice versa, given that they have different optical absorption properties and singlet oxygen quantum yields for PDT. Specifically, we demonstrate in two oral squamous cell carcinoma lines (FaDu and SCC4) that ICG has minimal effect on BPD PDT efficacy when irradiated with either a continuous or pulsed laser. Furthermore, the impact of BPD on ICG photodegradation was monitored with PAI in tissue-mimicking phantoms. These studies inform us that the combination of BPD and ICG can be utilized for PAI-guided PDT. However, researchers need to consider the photodegradation effects of ICG in the presence of BPD when designing their drug delivery strategies for PAI-guided PDT.

Capping gold nanoparticles with albumin to improve their biomedical properties

Nanotechnology is an emerging field which has created great opportunities either through the creation of new materials or by improving the properties of existing ones. Nanoscale materials with a wide range of applications in areas ranging from engineering to biomedicine have been produced. Gold nanoparticles (AuNPs) have emerged as a therapeutic agent, and are useful for imaging, drug delivery, and photodynamic and photothermal therapy. AuNPs have the advantage of ease of functionalization with therapeutic agents through covalent and ionic binding. Combining AuNPs and other materials can result in nanoplatforms, which can be useful for biomedical applications. Biomaterials such as biomolecules, polymers and proteins can improve the therapeutic properties of nanoparticles, such as their biocompatibility, biodistribution, stability and half-life. Serum albumin is a versatile, non-toxic, stable, and biodegradable protein, in which structural domains and functional groups allow the binding and capping of inorganic nanoparticles. AuNPs coated with albumin have improved properties such as greater compatibility, bioavailability, longer circulation times, lower toxicity, and selective bioaccumulation. In the current article, we review the features of albumin, as well as its interaction with AuNPs, focusing on its biomedical applications.

Microfluidics-Prepared Uniform Conjugated Polymer Nanoparticles for Photo-Triggered Immune Microenvironment Modulation and Cancer Therapy

Photothermal therapy (PTT) has shown great promise to spatiotemporally ablate cancer cells, and further understanding of the immune system response to PTT treatment would contribute to improvement in therapeutic outcomes. Herein, we utilize microfluidic technology to prepare biocompatible conjugated polymer nanoparticles (CP NPs) as PTT agents and assess the immune response triggered by CP-based PTT treatment in vitro and in vivo. Through careful control of the antisolvent, CP NPs with a uniform diameter of 52 nm were obtained. The c-RGD-functionalized CP NPs exhibit high photothermal conversion efficiency, inducing effective cancer cell death under an 808 nm laser illumination. Using macrophage cells as the model, CP NPs demonstrate effective activation of proinflammatory immune response. Furthermore, in tumor-bearing mice model, a single round of CP NP-assisted PTT could efficiently induce antitumor immunity activation and ultimately inhibit tumor growth. The study provides detailed understanding of both microfluidic technology for CP NP fabrication and photothermal-triggered antitumor immune responses.

Aptamer-Conjugated Au Nanocage/SiO2 Core-Shell Bifunctional Nanoprobes with High Stability and Biocompatibility for Cellular SERS Imaging and Near-Infrared Photothermal Therapy

The combination of surface-enhanced Raman scattering (SERS) imaging technology with near-infrared (NIR) light-triggered photothermal therapy is of utmost importance to develop novel theranostic platforms. Herein, an aptamer-conjugated Au nanocage/SiO₂ (AuNC/SiO₂/Apt) core-shell Raman nanoprobe has been rationally designed as the bifunctional theranostic platform to fulfill this task. In this theranostic system, the Raman-labeled Au nanocage (AuNC) was encapsulated into a bioinert shell of SiO₂, followed by conjugating aptamer AS1411 as the target-recognition moiety. AuNC served as the SERS-active and photothermal substrate due to its large free volume, built-in plasmon effect, and NIR photothermal capacity, while the SiO₂ coating endowed the nanoprobes with good stability and biocompatibility, as well as abundant anchoring sites for surface functionalization. Considering their prominent SERS and photothermal properties, the application potential of the AuNC/SiO₂/Apt nanoprobes was investigated. The proposed nanoprobes could be applied to targeted detection and SERS imaging of nucleolin-overexpressing cancer cells (MCF-7 cells as the model) from normal cells and also exhibited acceptable photothermal efficacy without systematic toxicity. This theranostic nanoplatform provided a possible opportunity for in situ diagnosis and noninvasive treatment of cancer cells by SERS imaging-guided photothermal therapy.

Self-assembly of nanoparticles by human serum albumin and photosensitizer for targeted near-infrared emission fluorescence imaging and effective phototherapy of cancer

A self-assembly nanoplatform of HSA@Cy-HPT for targeted near-infrared emission fluorescence imaging and effective phototherapy of cancer.

Continuous processing of phase-change materials into uniform nanoparticles for near-infrared-triggered drug release

We report a method based on interfacial, anti-solvent-induced precipitation in a fluidic device for the continuous and scalable processing of phase-change materials (PCMs) into uniform nanoparticles with controlled diameters in the range of 10-100 nm. A eutectic mixture of lauric acid and stearic acid, with a well-defined melting point at 39 °C, serves as an example to demonstrate the concept. In the fluidic device, a coaxial flow is created by introducing a PCM solution in ethanol and a lipid solution in water (the anti-solvent) as the focused and focusing phases, respectively. The formation of lipid-capped PCM nanoparticles is governed by diffusion-controlled mixing of ethanol and water. During the production, both doxorubicin (DOX, an anticancer drug) and indocyanine green (ICG, a near-infrared dye) can be readily loaded into the PCM nanoparticles to give a smart drug release system. Upon irradiation with near-infrared light, the photothermal heating caused by ICG can melt the PCM and thereby trigger the release of DOX. This work not only provides a new technique for the continuous processing of PCMs and other soft materials into uniform nanoparticles with controlled sizes but also demonstrates a biocompatible system for controlled release and related applications.

Homologous Gold Nanoparticles and Nanoclusters Composites with Enhanced Surface Raman Scattering and Metal Fluorescence for Cancer Imaging

A large number of deaths from cancer can be attributed to the lack of effective early-stage diagnostic techniques. Thus, accurate and effective early diagnosis is a major research goal worldwide. With the unique phenomenon of localized surface plasmon resonance (LSPR), plasmonic nanomaterials have attracted considerable attention for applications in surface-enhanced Raman scattering (SERS) and metal-enhanced fluorescence (MEF). Both SERS and MEF are ultra-sensitive methods for the detection and identification of early tumor at molecular level. To combine the merits of the fast and accurate imaging of MEF and the stable and clear imaging of SERS, we propose a novel dual functional imaging nanoprobe based on gold nanoparticles and gold nanocluster composites (denoted AuNPC-RGD). The gold nanoparticles are used as LSPR substrates to realized enhancement of Raman or fluorescence signal, while the gold nanoclusters serve as a fluorophore for MEF imaging, and exhibit better biocompatibility and stability. Furthermore, target molecule of cyclic Arg-Gly-Asp (cRGD) is incorporated into the composite to improve delivery efficiency, selectivity and imaging accuracy. These integrated properties endow AuNPC-RGD composites with outstanding biocompatibility and excellent imaging abilities, which could be used to achieve accurate and effective diagnosis for early cancer.

Laser-Activated Bioprobes with High Photothermal Conversion Efficiency for Sensitive Photoacoustic/Ultrasound Imaging and Photothermal Sensing

Laser-activated bioprobes with high photothermal conversion efficiency (IRPDA@PFH NDs) based on biocompatible IR-780 doped polydopamine perfluorocarbon nanodroplets (NDs) were developed. When protected by gelatin microspheres, their near-spherical morphologies can be easily observed with transmission electron microscope. Doping IR-780 (3 w/w % of added dopamine hydrochloride) can significantly enhance near-infrared (NIR) absorption and photothermal conversion efficiency to 57.7%. The enhanced NIR absorption and nonradiative relaxation are preferred to stronger photoacoustic (PA) signals and higher PA imaging definition; ultrasound (US) signals also increase more than 2.5 times because of easier phase change of NDs. These bioprobes had sensitive PA/US imaging capability with highly effective substitute utilizations, in which polydopamine was used either as a PA contrast or a photothermal agent. Perfluorocarbon can be used as an US contrast agent and temperature indicator. More importantly, the gray value increments of US increase with temperature in a general range from 35 to 55 °C. Especially, an approximate linear increasing of gray value in the optimized photothermal therapy (PTT) range from 35 °C to 50 °C could be used for the temperature monitoring and control of PTT. During PTT, the heated regions and the extent of photothermal heating can be visualized by US imaging. These findings indicate their great potential for biosensing and PTT monitoring.

Developing Hollow-Channel Gold Nanoflowers as Trimodal Intracellular Nanoprobes

Gold nanoparticles-enabled intracellular surface-enhanced Raman spectroscopy (SERS) provides a sensitive and promising technique for single cell analysis. Compared with spherical gold nanoparticles, gold nanoflowers, i.e., flower-shaped gold nanostructures, can produce a stronger SERS signal. Current exploration of gold nanoflowers for intracellular SERS has been considerably limited by the difficulties in preparation, as well as background signal and cytotoxicity arising from the surfactant capping layer. Recently, we have developed a facile and surfactant-free method for fabricating hollow-channel gold nanoflowers (HAuNFs) with great single-particle SERS activity. In this paper, we investigate the cellular uptake and cytotoxicity of our HAuNFs using a RAW 264.7 macrophage cell line, and have observed effective cellular internalization and low cytotoxicity. We have further engineered our HAuNFs into SERS-active tags, and demonstrated the functionality of the obtained tags as trimodal nanoprobes for dark-field and fluorescence microscopy imaging, together with intracellular SERS.

Exploring the margins of SERS in practical domain: An emerging diagnostic modality for modern biomedical applications

Excellent multiplexing capability, molecular specificity, high sensitivity and the potential of resolving complex molecular level biological compositions augmented the diagnostic modality of surface-enhanced Raman scattering (SERS) in biology and medicine. While maintaining all the merits of classical Raman spectroscopy, SERS provides a more sensitive and selective detection and quantification platform. Non-invasive, chemically specific and spatially resolved analysis facilitates the exploration of SERS-based nano probes in diagnostic and theranostic applications with improved clinical outcomes compared to the currently available so called state-of-art technologies. Adequate knowledge on the mechanism and properties of SERS based nano probes are inevitable in utilizing the full potential of this modality for biomedical applications. The safety and efficiency of metal nanoparticles and Raman reporters have to be critically evaluated for the successful translation of SERS in to clinics. In this context, the present review attempts to give a comprehensive overview about the selected medical, biomedical and allied applications of SERS while highlighting recent and relevant outcomes ranging from simple detection platforms to complicated clinical applications.

Facile synthesis of gold trisoctahedral nanocrystals with controllable sizes and dihedral angles

Shape-controlled synthesis of Au nanocrystals is of paramount importance to their applications in plasmonics, catalysis, and nanomedicine. While the synthesis of Au nanocrystals enclosed by low-index facets has been greatly advanced over the past two decades, only limited progress has been made for their high-index counterparts. Here we report a robust route to the facile synthesis of Au trisoctahedral nanocrystals enclosed by high-index facets. Unlike the previously reported methods, our synthesis was conducted at room temperature, together with the introduction a new Au(iii) precursor that was much harder to reduce than AuCl4-. In the setting of seed-mediated growth, the trisoctahedral nanocrystals could be readily prepared with sizes controllable from 20-80 nm and dihedral angles tunable in the range of 120-180 degrees. We further used computational modeling to demonstrate that the surface-functionalized Au trisoctahedral nanocrystal could outperform its spherical counterpart in terms of endocytic efficacy under identical conditions.

PA/US dual-modality imaging to guide VEGFR-2 targeted photothermal therapy using ZnPc-/PFH-loaded polymeric nanoparticles

Angiogenesis is a common pathological characteristic of many solid tumors and vulnerable atherosclerotic plaques.

Förster Resonance Energy Transfer-Based Dual-Modal Theranostic Nanoprobe for In Situ Visualization of Cancer Photothermal Therapy

The visualization of the treatment process in situ could facilitate to accurately monitor cancer photothermal therapy (PTT), and dramatically decrease the risk of thermal damage to normal cells and tissues, which represents a major challenge for cancer precision therapy. Herein, we prepare theranostic nanoprobes (NPs) for Förster resonance energy transfer (FRET)-based dual-modal imaging-guided cancer PTT, and clear visualization of the therapeutic process. The FRET-based theranostic NPs exhibit high FRET efficiency (88.2%), good colloidal stability, and tumor-targeting ability. Tumor tissue and surrounding blood vessels are visualized clearly by FRET-based NIR fluorescence imaging with a high signal-to-background ratio (14.5) and photoacoustic imaging with an excellent resolution at 24 h post injection of NPs. Under the guidance of dual-modal imaging, the NPs-induced photothermal effect selectively destructs cancer cells, simultaneously decreasing the FRET efficiency and leading to fluorescence and photoacoustic signal changes. The sensitive self-feedback process enables the in situ visualization of therapeutic process and precision guidance of in vivo cancer PTT. A high therapeutic efficacy and minimum side effects are achieved in C6 tumor-bearing nude mice, holding great promise for precision therapy and cancer theranostics.