Combined Photothermal and Surface-Enhanced Raman Spectroscopy Effect from Spiky Noble Metal Nanoparticles Wrapped within Graphene-Polymer Layers: Using Layer-by-layer Modified Reduced Graphene Oxide as Reactive Precursors

Graphene Oxide Nanoparticles for Photothermal Treatment of Hepatocellular Carcinoma Using Low-Intensity Femtosecond Laser Irradiation

Graphene oxide-mediated photothermal therapy using femtosecond lasers has recently shown promise in treating hepatocellular carcinoma. However, significant work remains to optimize irradiation parameters for specific nanoparticle types and cancer cells to improve nanomaterial-mediated photothermal anticancer therapy. This study investigated the photothermal potential of nGO and nGO-PEG nanoparticles (NPs) combined with femtosecond laser irradiation at 515 nm and 1030 nm wavelengths, with varying power (0.1 and 0.2 W/cm2) and duration (5 and 10 min), to optimize photothermal therapy for hepatocellular carcinoma. Conversion efficiency of NPs, morphology and viability of HepG2 and normal MDCK cells after treatments were evaluated using an electronic thermometer, phase-contrast microscopy, and WST-1 assay. The results revealed that nGO-PEG NPs exhibited better photothermal efficiency than nGO, with 515 nm of irradiation inducing a temperature increase up to 19.1 °C compared to 4.7 °C with 1030 nm of light. Laser exposure to 515 nm significantly reduced HepG2 cell viability, with the most intense conditions (10 min at 0.2 W/cm2) causing a decrease of up to 58.2% with nGO and 43.51% with nGO-PEG. Normal MDCK cells showed minimal impact or a slight viability increase, especially with nGO-PEG. Combined treatment with laser irradiation and NPs induced significant morphological changes in HepG2 cells, including cell detachment and apoptotic-like characteristics, particularly with 1030 nm of irradiation. MDCK cells exhibited minimal morphological changes, with some recovery observed under lower energy conditions. These findings suggest that low-energy lasers and engineered nanomaterials could provide a minimally invasive approach to photothermal cancer therapy with reduced side effects.

Surface-Enhanced Raman Scattering Using 2D Materials

The use of surface-enhanced Raman scattering (SERS) as a technique for detecting small amounts of (bio)chemical analytes has become increasingly popular in various fields. While gold and silver nanostructures have been extensively studied as SERS substrates, the availability of other types of substrates is currently expanding the applications of this spectroscopic method. Recently, researchers have begun exploring two-dimensional (2D) materials (e. g., graphene-like nanostructures) as substrates for SERS analysis. These materials offer unique optical properties, a well-defined structure, and the ability to modify their surface chemistry. As a contribution to advance this field, this concept article highlights the significance of understanding the chemical mechanism that underlies the experimental Raman spectra of chemisorbed molecules onto 2D materials' surfaces. Therefore, the article discusses recent advancements in fabricating substrates using 2D layered materials and the synergic effects of using their metallic composites for SERS applications. Additionally, it provides a new perspective on using Raman imaging in developing 2D materials as analytical platforms for Raman spectroscopy, an exciting emerging research area with significant potential.

One-step fabrication of flexible polyamide@Ag-dodecanethiol membranes for highly sensitive SERS detection of thiram

The surface-enhanced Raman scattering (SERS) is an effective spectral technology based on Raman scattering, but in practice, the commonly used SERS substrates suffer from low sensitivity and poor stability. In order to overcome these limitations, the SERS substrates were prepared from hydrophobic modification of dodecanethiol (C12) coupled with a flexible substrate, which was then used for pesticides detection in water. A flexible PA@Ag-C12 substrate with surface functionalization has been obtained. This work aims to investigate the self-assembly of Ag NPs modified with C12 onto polyamide (PA) membranes. Initially, transmission electron microscopy and scanning electron microscopy were used to analyze the substrate's morphology. Then with the help of an energy-dispersive spectrometer, sulfur content of C12-modified Ag NPs was analyzed. In order to determine the hydrophobicity of the modified Ag NPs, the contact angle was used. The results indicate that the gap between Ag NPs on PA membrane can be effectively controlled in order to prevent Ag NPs from aggregating. Furthermore, the finite-difference time-domain analysis indicated that the PA@Ag-C12 substrate exhibited a stronger electromagnetic enhancement effect than the PA@Ag substrate. By reducing NPs gaps on the PA membrane, the number of 'hot spots' increased, and the SERS performance of the substrate was improved as a result. According to the results of this study, this method can greatly reduce the manufacturing costs and time costs of the SERS substrate while maintaining the original uniformity. The SERS performance of PA@Ag-C12 was found to be three orders of magnitude better than that of PA@Ag direct self-assembled substrate, and the detection limit for Rhodamine 6G (R6G) was approximately 8.47 × 10-14M. On the basis of the PA@Ag-C12 substrate, thiram is detectable at a detection limit of 5.88 × 10-11M with a high degree of sensitivity and repeatability.

Bioactive NAD+ Regeneration Promoted by Multimetallic Nanoparticles Based on Graphene-Polymer Nanolayers

The concentration of nicotinamide adenine dinucleotide oxidized form (NAD⁺) changes during aging, and the production of NAD⁺ can significantly affect both health span and life span. However, it is still of great challenge to regenerate NAD⁺ from its precursors. Herein, we introduce a method to prepare multimetallic nanoparticles (including Au, Pt, Cu, and MgO) that can efficiently promote the conversion of NADH to NAD⁺. The nanoparticles are made by mixing reduced graphene oxide-polyethyleneimine-polyacrylic acid nano-films with metallic salts, where four different metal ions are reduced and grow at the surface of the nanolayers. The morphology, size, and growth rate of nanoparticles can be controlled by adding surfactants, applying an electric field, and so forth. Our multimetallic nanoparticles exhibit excellent catalytic performance that a complete conversion of NADH to NAD⁺ can be finished in 3 min without introducing additional oxygen. This work presents a way for the preparation of multimetallic nanoparticles to promote NAD⁺ regeneration, which shows great promise for the future design of high-performance materials for antiaging.

Graphene-Based Surface-Enhanced Raman Scattering (SERS) Sensing: Bibliometrics Based Analysis and Review

Surface-enhanced Raman scattering (SERS) has received increasing attention from researchers since it was first discovered on rough silver electrode surfaces in 1974 and has promising applications in life sciences, food safety, and environmental monitoring. The discovery of graphene has stirred considerable waves in the scientific community, attracting widespread attention in theoretical research and applications. Graphene exhibits the properties of a semi-metallic material and has also been found to have Raman enhancement effects such as in metals. At the same time, it quenches the fluorescence background and improves the ratio of a Raman signal to a fluorescence signal. However, graphene single-component substrates exhibit only limited SERS effects and are difficult to use for trace detection applications. The common SERS substrates based on noble metals such as Au and Ag can produce strong electromagnetic enhancement, which results in strong SERS signals from molecules adsorbed on the surface. However, these substrates are less stable and face the challenge of long-term use. The combination of noble metals and graphene to obtain composite structures was an effective solution to the problem of poor stability and sensitivity of SERS substrates. Therefore, graphene-based SERS has been a popular topic within the last decade. This review presents a statistically based analysis of graphene-based SERS using bibliometrics. Journal and category analysis were used to understand the historical progress of the topic. Geographical distribution was used to understand the contribution of different countries and institutions to the topic. In addition, this review describes the different directions under this topic based on keyword analysis and keyword co-occurrence. The studies on this topic do not show a significant divergence. The researchers’ attention has gradually shifted from investigating materials science and chemistry to practical sensing applications. At the end of the review, we summarize the main contents of this topic. In addition, several perspectives are presented based on bibliometric analysis.

Graphene Oxide Nanosheets for Localized Hyperthermia-Physicochemical Characterization, Biocompatibility, and Induction of Tumor Cell Death

BACKGROUND

The main goals of cancer treatment are not only to eradicate the tumor itself but also to elicit a specific immune response that overcomes the resistance of tumor cells against chemo- and radiotherapies. Hyperthermia was demonstrated to chemo- and radio-sensitize cancerous cells. Many reports have confirmed the immunostimulatory effect of such multi-modal routines.

METHODS

We evaluated the interaction of graphene oxide (GO) nanosheets; its derivatives reduced GO and PEGylated rGO, with components of peripheral blood and evaluated its thermal conductivity to induce cell death by localized hyperthermia.

RESULTS

We confirmed the sterility and biocompatibility of the graphene nanomaterials and demonstrated that hyperthermia applied alone or in the combination with radiotherapy induced much more cell death in tumor cells than irradiation alone. Cell death was confirmed by the release of lactate dehydrogenase from dead and dying tumor cells.

CONCLUSION

Biocompatible GO and its derivatives can be successfully used in graphene-induced hyperthermia to elicit tumor cell death.

Mesenchymal stem cell-derived microvesicles mediate BMP2 gene delivery and enhance bone regeneration

Microvesicles–polyethyleneimine/pDNA formed via layer-by-layer self-assembly increase the delivery of hBMP2 plasmids and enhance bone repair.

Spontaneous Growth of 3D Silver Mesoflowers on Poly(4-vinylpyridine) Brushes-Grafted-Graphene Oxide Films and Facile Creation of Nanoporosities over their Surface

Fabricating three-dimensional (3D) hierarchical noble-metal particles by spontaneous redox reactions between graphene and noble-metal salts still remains a great challenge. Herein, the fact that graphene oxide (GO) itself acts as both a platform for grafting polymer brushes and a reducing agent to reduce [Ag(NH₃ )₂ ]⁺ ions is taken advantages of. 3D flower-like Ag mesoparticles (Ag mesoflowers, Ag MFs) with tunable size and shapes can spontaneous grow on poly(4-vinylpyridine) brushes-grafted-graphene oxide (P4VP-g-GO) films in Ag(NH₃ )₂ OH solution without the use of any additional reducing agent. The residual Ag(NH₃ )₂ OH on 3D Ag MFs surface can be further reduced by NaBH₄ , causing abundant nanoporosities over the entire Ag MFs. The resulting Ag nanoporous MFs (Ag NMFs) with larger surface-to-volume ratio and higher nanoscale roughness exhibit ultrasensitivity in surface-enhanced Raman spectroscopy (SERS) detection, and the detection limit for 4-aminothiophenol is as low as 10^-13  m.

Using a Graphene-Polyelectrolyte Complex Reducing Agent To Promote Cracking in Single-Crystalline Gold Nanoplates

It is a challenge to produce single-crystalline gold nanoparticles having regular size definition designed for controlled light absorbance and internal structural inhomogeneities to enhance electro-magnetic fields. Here, we report a synthetic strategy to generate large single-crystalline triangular or hexagonal gold nanoplates with multiple cracks within the plates using a graphene-polyelectrolyte complex as both a surface adsorbent and bulk reducing agent. Large-scale gold nanoplates can be synthesized within 48 h. First-principles calculations indicate that the nanoplates have a kinetically limited morphology resulting from prior growth of {111} facets confined by the graphene-polyelectrolyte multilayer. The nanocracks result from the inability of the bulk reducing agent to enter narrow defect spaces during growth that remained permanently. The nanoplates had extraordinary physical-chemical detection sensitivity when used for surface-enhanced Raman scattering (SERS) and surface-enhanced infrared absorption (SEIRA). The limit of rhodamine 6G (Rh6G) SERS detection is as low as 5 × 10^-13 M. The gold nanoplates also showed a remarkable light-to-heat conversion efficiency (68.5%). The approach described may be applicable to other metals so that tunable nanostructures can be generated by the graphene-polyelectrolyte multilayer strategy.

Efficient capture and photothermal ablation of planktonic bacteria and biofilms using reduced graphene oxide-polyethyleneimine flexible nanoheaters

Bacterial infections are one of the leading causes of disease worldwide. Conventional antibiotics are becoming less efficient, due to antibiotic-resistant bacterial strains. Therefore, the development of novel antibacterial materials and advanced treatment strategies are becoming increasingly important. In the present work, we developed a simple and efficient strategy for effective bacterial capture and their subsequent eradication through photothermal killing. The developed device consists of a flexible nanoheater, comprising a Kapton/Au nanoholes substrate, coated with reduced graphene oxide-polyethyleneimine (K/Au NH/rGO-PEI) thin films. The Au NH plasmonic structure was tailored to feature strong absorption in the near-infrared (NIR) region, where most biological matter has limited absorption, while PEI was investigated for its strong binding with bacteria through electrostatic interactions. The K/Au NH/rGO-PEI device was demonstrated to capture and eliminate effectively both planktonic Gram-positive Staphilococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) bacteria after 10 min of NIR (980 nm) irradiation and, to destroy and eradicate Staphilococcus epidermidis (S. epidermidis) biofilms after 30 min irradiation. The technique developed herein is simple and universal with potential applications for eradication of different micro-organisms.

Multiple-Enzyme Graphene Microparticle Presenting Adaptive Chemical Network Capabilities

Interrelated reaction networks steered by multiple types of enzymes are among the most intriguing enzyme-based cellular features. These reaction networks display advanced features such as adaptation, stimuli-responsiveness, and decision-making in accordance with environmental cues. However, artificial enzyme particles are still deficient in network-level capabilities, mostly because delicate enzymes are difficult to immobilize and assemble. In this study, we propose a general strategy to prepare enzyme-based particles that demonstrate network reaction capability. We assembled multiple types of proteins with a nanoscopic binder prepared from polyelectrolyte and graphene. After assembly, the enzymes all preserved their catalytic capabilities. By incorporating multiple types of enzymes, the particles additionally displayed network-reaction capabilities. We were able to use NIR irradiations to quasi-reversibly adjust the catalytic abilities of these enzyme-based particles. In addition, after a biomimetic mineralization process was used to wrap the protein complexes in a MOF shell, the particles were more robust and catalytically active even after being immersed in acidic (pH 4) or basic (pH 10) solutions for 3 days. This study provides an insight into the study of network properties of functional enzyme particles experimentally and enriches scientific understanding of multifunctional or stimuli-responsive behaviors at the reaction network level. The building of artificial reaction networks possesses high potential in realizing intelligent microparticles that can perform complicated tasks.

The Fabrication of rGO/(PLL/PASP)3 @DOX Nanorods with pH-Switch for Photothermal Therapy and Chemotherapy

The development of well-controlled drug carriers that are stable and highly effective for the delivery of anticancer agents is challenging. Herein, we report a novel pH-controlled drug delivery system, utilizing reducing graphene oxide (rGO)-polymer self-assembly films as carriers, for the preparation of effective drug nanorods and nanoparticles. In this system, the rGO-polymer carriers were constructed by the alternating assembly of poly-l-lysine (PLL) and polyaspartic acid (PASP) around the rGO sheets. Furthermore, the rGO-polymer cores, which possess a positively charged surface as the desired template, could assemble with negatively charged doxorubicin (DOX) via electrostatic interactions. The DOX embedding efficiency and the morphology of the drug nanocomposites could be controlled by the number of rGO-polymer bilayers and concentration of the rGO-polymer bilayers and the initial DOX concentration. Importantly, the release of DOX could be regulated by controlling the pH and by using a NIR laser. Under acidic conditions, the interactions between the PASP layer and DOX molecules can be broken, resulting in gradual release of the DOX molecules. Upon NIR irradiation, the release of DOX could be further accelerated and a photothermal effect from rGO induced. Cellular uptake and cytotoxicity experiments indicate that the drug nanocomposites possess effective anticancer activity. Thus, in this work, we present a useful strategy for the fabrication of pH-responsive drug nanocomposites for combined photothermal and chemical therapy. The nanocomposite can be used as a potential drug delivery system for practical cancer treatment.

Fried egg-like Au mesostructures grown on poly(4-vinylpyridine) brushes grafted onto graphene oxide

Hierarchical Au mesostructures as SERS-active substrates were facilely fabricated by the reduction of HAuCl₄-loaded poly(4-vinylpyridine) brushes with ascorbic acid.

Controlled Interfacial Permeation, Nanostructure Formation, Catalytic Efficiency, Signal Enhancement Capability, and Cell Spreading by Adjusting Photochemical Cross-Linking Degrees of Layer-by-Layer Films

Interfacial properties including permeation, catalytic efficiency, Raman signal enhancement capabilities, and cell spreading efficiencies are important features that determine material functionality and applications. Here, we propose a facile method to adjust the above-mentioned properties by controlling the cross-linking degrees of multilayer using a photoactive molecule. After treating the cross-linked films in basic solutions, films with different cross-linking degrees presented varying residue thicknesses and film morphologies. As a result, these different films possessed distinct molecular loading and release characteristics. In addition, gold nanoparticles (AuNPs) of different morphological traits were generated by redox reactions coupled with diffusion within these films. The AuNP-polyelectrolyte obtained from the polyelectrolyte films of the medium cross-linking degrees displayed the highest catalytic efficiency and signal enhancement capabilities. Furthermore, cells responded to the variation of film cross-linking degrees, and on the films with the highest cross-linking degree, cells adhered with the highest speed. We expect this report to provide a general interfacial material engineering strategy for material designs.

Fuzzy, copper-based multi-functional composite particles serving simultaneous catalytic and signal-enhancing roles

Multifunctional plasmonic particles serving simultaneously as catalysts and label-free reporting agents are highly pursued due to their great potential in enhancing reaction operational efficiencies. Copper is an abundant and economic resource, and it possesses practical applicability in industries, but no dual-functional copper-based catalytic and self-reporting particles have been reported so far. This study proposes a facile strategy to prepare high-performance dual-functional copper-based composite particles that catalyze reactions and simultaneously serve as a SERS (surface enhanced Raman spectra) active, label-free reporting agent. Polyelectrolyte-modified reduced graphene oxide particles are used as the reactive precursors in the fabrication method. Upon adding Cu(NO3)2 solutions into the precursor dispersions, composite particles comprised by copper/copper oxide core and polyelectrolyte-graphene shell were facilely obtained under sonication. The as-prepared composite particles efficiently catalyzed the conversion of 4-nitrophenol to 4-aminophenol and simultaneously acted as the SERS-active substrate to give enhanced Raman spectra of the produced 4-aminophenol. Taking advantage of the assembling capabilities of polyelectrolyte shells, the composite particles could be further assembled onto a planar substrate to catalyze organic reactions, facilitating their application in various conditions. We expect this report to promote the fabrication and application of copper-based multifunctional particles.

Non-covalent modification of graphene oxide nanocomposites with chitosan/dextran and its application in drug delivery

Graphene oxide nanosheets non-covalent functionalized with chitosan/dextran was successfully developed via LbL self-assembly technique for anti-cancer drug delivery application.