Optically controlled hybrid metamaterial of plasmonic spiky gold inbuilt graphene sheets for bimodal imaging guided multimodal therapy

SERS-based microdevices for use as in vitro diagnostic biosensors

Advances in surface-enhanced Raman scattering (SERS) detection have helped to overcome the limitations of traditional in vitro diagnostic methods, such as fluorescence and chemiluminescence, owing to its high sensitivity and multiplex detection capability. However, for the implementation of SERS detection technology in disease diagnosis, a SERS-based assay platform capable of analyzing clinical samples is essential. Moreover, infectious diseases like COVID-19 require the development of point-of-care (POC) diagnostic technologies that can rapidly and accurately determine infection status. As an effective assay platform, SERS-based bioassays utilize SERS nanotags labeled with protein or DNA receptors on Au or Ag nanoparticles, serving as highly sensitive optical probes. Additionally, a microdevice is necessary as an interface between the target biomolecules and SERS nanotags. This review aims to introduce various microdevices developed for SERS detection, available for POC diagnostics, including LFA strips, microfluidic chips, and microarray chips. Furthermore, the article presents research findings reported in the last 20 years for the SERS-based bioassay of various diseases, such as cancer, cardiovascular diseases, and infectious diseases. Finally, the prospects of SERS bioassays are discussed concerning the integration of SERS-based microdevices and portable Raman readers into POC systems, along with the utilization of artificial intelligence technology.

Nanoarchitectonics of photothermal materials to enhance the sensitivity of lateral flow assays

Lateral flow assays (LFAs) are currently the most widely used point-of-care testing technique with remarkable advantages such as simple operation, rapid analysis, portability, and low cost. Traditionally, gold nanoparticles are employed as tracer element in LFAs due to their strong localised surface plasmon resonance. However, this conventional LFA technique based on colorimetric analysis is neither useful to determine critical analytes with desired sensitivity, nor can it quantify the analytes. Various signal amplification strategies have been proposed to improve the sensitivity and the quantitative determination of analytes using LFAs. One of the promising strategies is to enhance the photothermal properties of nanomaterials to generate heat after light irradiation, followed by a temperature measurement to detect and quantify the analyte concentration. Recently, it has been observed that the nanoscale architecture of materials, including size, shape, and nanoscale composition, plays a significant role in enhancing the photothermal properties of nanomaterials. In this review, we discuss the nanoarchitectonics of nanomaterials regarding enhanced photothermal properties and their application in LFAs. Initially, we discuss various important photothermal materials and their classification along with their working principle. Then, we highlight important aspects of the nanoscale architecture (i.e., size, shape, and composition) to enable maximum light-to-heat conversion efficiency. Finally, we discuss some of the recent advances in photothermal LFAs and their application in detecting analytes.

Modulation of hypoxia and redox in the solid tumor microenvironment with a catalytic nanoplatform to enhance combinational chemodynamic/sonodynamic therapy

The efficacy of reactive oxygen species-mediated therapy is generally limited by hypoxia and overexpressed glutathione (GSH) in the tumor microenvironment (TME). To address these issues, herein, a smart Mn₃O₄/OCN-PpIX@BSA nanoplatform is rationally developed to enhance the combinational therapeutic efficacy of chemodynamic therapy (CDT) and sonodynamic therapy (SDT) through TME modulation. For constructing the catalytic nanoplatform (Mn₃O₄/OCN-PpIX@BSA), Mn₃O₄ nanoparticles were grown in situ on oxidized g-C₃N₄ (OCN) nanosheets, and the as-prepared Mn₃O₄/OCN nano-hybrids were then successively loaded with protoporphyrin (PpIX) and coated with bovine serum albumin (BSA). The catalase-like Mn₃O₄ nanoparticles are able to effectively catalyze the overexpressed endogenous H₂O₂ to produce O₂, which could relieve hypoxia and improve the therapeutic effect of combinational CDT/SDT. The decomposition of Mn₃O₄ by GSH enables the release of Mn²⁺ ions, which not only facilitates good T₁/T₂ dual-modal magnetic resonance imaging for tumor localization but also results in the depletion of GSH and the Mn²⁺-driven Fenton-like reaction, thus further amplifying the oxidative stress and achieving improved therapeutic efficacy. It is worth noting that the Mn₃O₄/OCN-PpIX@BSA nanocomposites exhibit minimal toxicity to normal tissues at therapeutic doses. These positive findings provide a new strategy for the convenient construction of TME-regulating smart theranostic nanoagents to improve the therapeutic outcomes towards malignant tumors effectively.

A nanoarchitecture of a gold cluster conjugated gold nanorod hybrid system and its application in fluorescence imaging and plasmonic photothermal therapy

Engineering different nanomaterials into a single functional material can impart unique properties of the parental nanoparticles, especially in the field of bio imaging and therapy. Gold nanomaterials having different sizes, shapes and dimensionalities exhibit exceptional properties apart from their non-toxicity and hence are strong candidates in the biomedical field. Designing a hybrid nanomaterial of two gold nanostructures retaining the individual properties of the parental nanomaterials is challenging. Here, we demonstrate the synthesis of a hybrid nanomaterial (GQC@GNR), comprising an extremely small gold nanocluster and a representative of the asymmetric gold nanostructure, i.e., a gold nanorod, both having their own different exclusive optical properties like tuneable emission and NIR absorption characteristics, respectively. The hybrid system is designed to retain its emission and absorption in the NIR region to use it as an agent for simultaneous imaging and therapy. The formation of GQC@GNR and its architectonics heavily depend on the synthesis route and the parameters adopted which in turn have a direct influence on its properties. The architecture and its connection to the optical properties are explained using UV-Vis absorption and photoluminescence spectroscopy, zeta potential, transmission electron microscopy, etc. DFT-based computational modelling supports architectonics as explained by the experimental findings. The formation of the gold-gold hybrid system witnessed interesting science with a strong indication that materials with desired properties can be designed by appropriately modulating the architectonics of hybrid formation. Finally, folate conjugated GQC@GNR demonstrated its efficacy for targeted imaging and photothermal therapy in HeLa cells and tumor-bearing animal models. The detailed therapeutic efficacy of GQC@GNR is also explained based on Raman spectroscopy.

Synergistic Effect of Oxygen- and Nitrogen-Containing Groups in Graphene Quantum Dots: Red Emitted Dual-Mode Magnetic Resonance Imaging Contrast Agents with High Relaxivity

Contrast agents (CAs) in magnetic resonance imaging generally involve the dissociative Gd³⁺. Because of the limited ligancy of Gd³⁺, the balance between Gd³⁺ coordination stability (reducing the concentration of dissociative Gd³⁺) and increases in the number of coordination water molecules (enhancing the relaxivity) becomes crucial. Herein, the key factor of the synergistic effect between the O- and N-containing groups of graphene quantum dots for the structural design of CAs with both high relaxivity and low toxicity was obtained. The nitrogen-doped graphene quantum dots (NGQDs) with an O/N ratio of 0.4 were selected to construct high-relaxivity magnetic resonance imaging (MRI)-fluorescence dual-mode CAs. The coordination stability of Gd³⁺ can be increased through the synergetic coordination of O- and N-containing groups. The synergetic coordination of O- and N-containing groups can result in the short residency time of the water ligand and achieve high relaxivity. The resulting CAs (called NGQDs-Gd) exhibit a high relaxivity of 32.04 mM^-1 s^-1 at 114 μT. Meanwhile, the NGQDs-Gd also emit red fluorescence (614 nm), which can enable the MRI-fluorescence dual-mode imaging as the CAs. Moreover, the bio-toxicity and tumor-targeting behavior of NGQDs-Gd were also evaluated, and NGQDs-Gd show potential in MRI-fluorescence imaging in vivo.

Chemical Modification of Chitosan for Developing Cancer Nanotheranostics

Cancer is a worldwide public health issue that has not been conquered. Theranostics, the combination of a therapeutic drug and imaging agent in one formulation using nanomaterials, has been developed to better cure cancer in recent years. Although diverse biomaterials have been applied in cancer theranostics, chitosan (CS), a natural polysaccharide bearing easy modification sites with excellent biocompatibility and biodegradability, shows great potential for developing cancer nanotheranostics. In this review, we seek to describe the chemical functionalities of CS used in cancer theranostics and their synthesis methods. We also present recent discoveries and research progresses on how the CS functionalization could improve the delivery efficiency of CS-based nanotheranostics. Finally, we report several case studies about the application of CS-based nanotheranostics. This paper focuses on the strategies to construct CS-based theranostics systems via chemical routes and highlights their applications in cancer treatment, which can provide useful references for further studies.

Tumor microenvironment responsive self-cascade catalysis for synergistic chemo/chemodynamic therapy by multifunctional biomimetic nanozymes

Chemodynamic therapy (CDT) is an emerging approach to treat cancer based on the tumor microenvironment (TME), but its limited content of endogenous hydrogen peroxide (H₂O₂) weakens the anticancer effects. Herein, a multifunctional biomimetic nanozyme (Se@SiO₂-Mn@Au/DOX, named as SSMA/DOX) is fabricated, which undergoes TME responsive self-cascade catalysis to facilitate MRI guided enhanced chemo/chemodynamic therapy. The SSMA/DOX nanocomposites (NCs) responsively degrade in acidic conditions of tumor to release Se, DOX, Au and Mn²⁺. Mn²⁺ not only enables MRI to guided therapy, but also catalyzes the endogenous H₂O₂ into hydroxyl radical (˙OH) for CDT. In addition, the Au NPs continuously catalyze glucose to generate H₂O₂, enhancing CDT by supplementing a sufficiently reactive material and cutting off the energy supply of the tumor by consuming glucose. Simultaneously, Se enhances the chemotherapy of doxorubicin hydrochloride (DOX) and CDT by upregulating ROS in the tumor cells, achieving remarkable inhibition effect towards tumor. Moreover, SSMA/DOX NCs have good biocompatibility and degradability, which avoid long-term toxicity and side effects. Overall, the degradable SSMA/DOX NCs provide an innovative strategy for tumor microenvironment responsive self-cascade catalysis to enhance tumor therapy.

A lipid droplet specific fluorescent probe for image-guided photodynamic therapy under hypoxia

Photodynamic therapy (PDT) is a potential strategy for many superficial, esophageal, intestinal, and bronchial cancer treatments, but its therapeutic effect is limited by a lack of specificity and the hypoxic tumor environment. It is necessary to develop novel photosensitizers (Ps) with organelles targeting and the ability to generate cytotoxic species under light irradiation without the presence of oxygen. Herein, we designed and synthesized a biocompatible fluorescent Ps CPNBD for lipid droplets (LDs) fluorescence (FL) image-guided PDT. CPNBD showed FL quenching in water but FL was significantly turned on by oil with a remarkable FL enhancement compared to that in aqueous solution. Due to its strong lipophilicity (Clog P of 7.96), CPNBD could specifically stain the LDs of human clear cell renal cell carcinoma (ccRCC) tumor cells and tissues with good photostability. Meanwhile, CPNBD could efficiently generate cytotoxic reactive oxygen species under low-power white-light irradiation, which could efficiently damage DNA via a PDT process with great tumor suppression ability in vitro and in vivo. Thus, this work provides a novel strategy for designing LD-targeting Ps with efficient image-guided PDT under the tumor hypoxic environment.

Nanohybrids of Magnetically Intercalated Optical Metamaterials for Magnetic Resonance/Raman Imaging and In Situ Chemodynamic/Photothermal Therapy

Target-specific reactive oxygen species (ROS)-based cancer treatments with high therapeutic efficacy and minimal side effects have been identified recently as a potentially effective cancer management strategy. Herein, we report the fabrication of a targeted nanotheranostic agent built on an iron oxide nanoparticle-decorated graphene-gold hybrid [plasmonic magnetic nanoprobe (PMNP)] for self-guided magnetic resonance (MR)/surface-enhanced Raman scattering imaging and photothermal therapy (PTT)/chemodynamic therapy (CDT). In the presence of glutathione, which is abundant in the tumor environment, the iron oxide nanoparticles undergo in situ reduction, which in turn generates hydroxyl radicals via a Fenton reaction to realize targeted destruction of tumor cells. Moreover, the localized production of heat benefited from the near-infrared absorption of the PMNP accelerates the intratumoral ROS generation process, with a synergistic effect of CDT/PTT. Furthermore, the probe offers an accurate visualization of the intracellular localization of the material through SERS/MR dual imaging channels. In view of the advantages offered by the tumor-specific stimuli-responsive nature of the probe, the PMNP presents as an effective tool for cancer management.

Elucidating Gold-MnO2 Core-Shell Nanoenvelope for Real Time SERS-Guided Photothermal Therapy on Pancreatic Cancer Cells

Pancreatic cancer represents one of the most aggressive in nature with a miserable prognosis that warrants efficient diagnostic and therapeutic interventions. Herein, a MnO₂ overlaid gold nanoparticle (AuNPs) based photothermal theranostic nanoenvelope (PTTNe:MnO₂@AuNPs) was fabricated to substantiate surface-enhanced Raman spectroscopy (SERS) guided real-time monitoring of photothermal therapy (PTT) in pancreatic cancer cells. A sharp enhancement of the fingerprint Raman signature of MnO₂ at 569 cm^-1 exhibited as a marker peak for the first time to elucidate the intracellular PTT event. In this strategic design, the leftover bare AuNPs after the degradation of the MnO₂ layer from the nanoenvelope in the presence of intracellular H₂O₂ enabled real-time tracking of biomolecular changes of Raman spectral variations during PTT. Moreover, the surface of the as-synthesized nanoenvelope was functionalized with a pancreatic cancer cell targeting peptide sequence for cholecystokinin fashioned the PTTNe with admirable stability and biocompatibility. Finally, the precise cell death mechanism was explicitly assessed by SERS spectral analysis as a complementary technique. This targeted phototheranostic approach demonstrated in pancreatic cancer cells presented a therapeutically viable prototype for futuristic personalized cancer nanomedicine.

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.

Elucidating a Thermoresponsive Multimodal Photo-Chemotherapeutic Nanodelivery Vehicle to Overcome the Barriers of Doxorubicin Therapy

In an attempt to circumvent the major pitfalls associated with conventional chemotherapy including drug resistance and off-target toxicity, we have adopted a strategy to simultaneously target both mitochondrial DNA (Mt-DNA) and nuclear DNA (n-DNA) with the aid of a targeted theranostic nanodelivery vehicle (TTNDV). Herein, folic acid-anchored p-sulfo-calix[4]arene (SC₄)-capped hollow gold nanoparticles (HGNPs) were meticulously loaded with antineoplastic doxorubicin (Dox) and its mitochondrion-targeted analogue, Mt-Dox, in a pretuned ratio (1:100) for sustained thermoresponsive release of cargo. This therapeutic strategy was enabled to eradicate both n-DNA and Mt-DNA leaving no space to develop drug resistance. The SC₄-capped HGNPs (HGNPSC₄) were experimented for the first time as a photothermal (PTT) agent with 61.6% photothermal conversion efficiency, and they generated tunable localized heat more efficiently than bare HGNPs. Moreover, the cavity of SC₄ facilitated the formation of an inclusion complex with folic acid to target the folate receptor expressing cancer cells and imparted enhanced biocompatibility. The as-synthesized TTNDV was demonstrated to be an ideal substrate for surface-enhanced Raman scattering (SERS) to monitor the molecular-level therapeutic progression in cells and a spheroidal model. A significant reduction in the tumor mass with a marked survival benefit was achieved in syngraft murine models through this synergistic photo-chemotherapy. Collectively, this multifunctional nanoplatform offers a robust approach to treat cancer without any scope of generating Dox resistance and off-target toxicity.

Broad spectrum antibacterial photodynamic and photothermal therapy achieved with indocyanine green loaded SPIONs under near infrared irradiation

Antimicrobial photodynamic therapy (aPDT) and antimicrobial photothermal therapy (aPTT) are promising local and effective alternative therapies for antibiotic resistant bacterial infections and biofilms.