Understanding Bacterial Resistance to Heavy Metals and Nanoparticles: Mechanisms, Implications, and Challenges

Antimicrobial resistance is a global health problem as it contributes to high mortality rates in several infectious diseases. To address this issue, engineered nanoparticles/nano-formulations of antibiotics have emerged as a promising strategy. Nanoparticles are typically defined as materials with dimensions up to 100 nm and are made of different materials such as inorganic particles, lipids, polymers, etc. They are widely dispersed in the environment through various consumer products, and their clinical applications are diverse, ranging from contrast agents in imaging to carriers for gene and drug delivery. Nanoparticles can also act as antimicrobial agents either on their own or in combination with traditional antibiotics to produce synergistic effects, earning them the label of "next-generation therapeutics." They have also shown great effectiveness against multidrug-resistant pathogens responsible for nosocomial infections. However, overexposure or prolonged exposure to sublethal doses of nanoparticles can promote the development of resistance in human pathogens. The resistance can arise from various factors such as genetic mutation, horizontal gene transfer, production of reactive oxygen species, changes in the outer membrane of bacteria, efflux-induced resistance, cross-resistance from intrinsic antibiotic resistance determinants, plasmid-mediated resistance, and many more. Continuous exposure to nanoparticles can also transform an antibiotic-susceptible bacterial pathogen into multidrug resistance. Considering all these, the current review focuses on the mode of action of different heavy metals and nanoparticles and possible mechanisms through which bacteria attain resistance towards these heavy metals and nanoparticles.

PEGylated Pemetrexed and PolyNIPAM Decorated Gold Nanoparticles: A Biocompatible and Highly Stable CT Contrast Agent for Cancer Imaging

This study describes a multifunctional nanoparticle platform for targeted CT imaging and therapy of cancers. Pemetrexed (conjugated with polyethylene glycol, MW 2000 Da) and polyNIPAM (PEGylated) were designed for targeted delivery to folate receptors and thermally ablated tumors, respectively. These moieties were coated on gold nanoparticles (7 and 30 nm), and the prepared compounds were characterized using 1H NMR, FT-IR, CHNS, DLS, TEM, TGA, and UV-vis. The resulting agents exhibited 2-4 times higher X-ray attenuation compared to Visipaque and demonstrated specific accumulation in tumor tissue (4T1 xenograft model) 90 min after injection in mice. The nanoparticles displayed anticancer activity against 4T1 and MDA-MB-231 breast cancer cells (IC50: 182.87 and 206.18 μg/mL) and good biocompatibility. Importantly, the platform showed excellent stability over a year and at pH 2-12 and temperature range of -78 to 40 °C, and a water-dichloromethane extraction method was optimized for efficient purification, facilitating large-scale production.

Electron-electron scattering limits thermal conductivity of metals under extremely high electron temperatures

We report on the thermal transport properties of noble metals (gold, silver and copper) under conditions of extremely high electron temperatures (that are on the order of the Fermi energy). We perform parameter-free density functional theory calculations of the electron temperature-dependent electron-phonon coupling, electronic heat capacities, and thermal conductivities to elucidate the strong role played by the excitation of the low lyingd-bands on the transport properties of the noble metals. Our calculations show that, although the three metals have similar electronic band structures, the changes in their electron-phonon coupling at elevated electron temperatures are drastically different; while electron-phonon coupling decreases in gold, it increases in copper and, it remains relatively unperturbed for silver with increasing electron temperatures of up to ∼60 000 K (or 5 eV). We attribute this to the varying contributions from acoustic and longitudinal phonon modes to the electron-phonon coupling in the three metals. Although their electron-phonon coupling changes with electron temperature, the thermal conductivity trends with electron temperature are similar for all three metals. For instance, the thermal conductivities for all three metals reach their maximum values (on par with the room-temperature values of some of the most thermally conductive semiconductors) at electron temperatures of ∼6000 K, and thereafter monotonically decrease due to the enhanced effect of electron-electron scattering for electronic states that are further away from the Fermi energy. As such, only accounting for electron-phonon coupling and neglecting electron-electron scattering can lead to large over-predictions of the thermal conductivities at extremely high electron temperatures. Our results shed light on the microscopic understanding of the electronic scattering mechanisms and thermal transport in noble metals under conditions of extremely high electron temperatures and, as such, are significant for a plethora of applications such as in plasmonic devices that routinely leverage hot electron transport.

A comprehensive review on the biomedical frontiers of nanowire applications

This comprehensive review examines the immense capacity of nanowires, nanostructures characterized by unbounded dimensions, to profoundly transform the field of biomedicine. Nanowires, which are created by combining several materials using techniques such as electrospinning and vapor deposition, possess distinct mechanical, optical, and electrical properties. As a result, they are well-suited for use in nanoscale electronic devices, drug delivery systems, chemical sensors, and other applications. The utilization of techniques such as the vapor-liquid-solid (VLS) approach and template-assisted approaches enables the achievement of precision in synthesis. This precision allows for the customization of characteristics, which in turn enables the capability of intracellular sensing and accurate drug administration. Nanowires exhibit potential in biomedical imaging, neural interfacing, and tissue engineering, despite obstacles related to biocompatibility and scalable manufacturing. They possess multifunctional capabilities that have the potential to greatly influence the intersection of nanotechnology and healthcare. Surmounting present obstacles has the potential to unleash the complete capabilities of nanowires, leading to significant improvements in diagnostics, biosensing, regenerative medicine, and next-generation point-of-care medicines.

Antibacterial Properties of an Experimental Dental Resin Loaded with Gold Nanoshells for Photothermal Therapy Applications

This study explored the chemical and antibacterial properties of a dental resin loaded with gold nanoshells (AuNPs) in conjunction with photothermal therapy (PTT) as a novel method against Streptococcus mutans (S. mutans) to prevent secondary caries. First, a 20-h minimum inhibitory concentration (MIC) assay was performed on solutions of AuNPs with planktonic S. mutans under an LED device and laser at 660 nm. Next, resin blends containing 0, 1 × 1010, or 2 × 1010 AuNPs/mL were fabricated, and the degree of conversion (DC) was measured using an FTIR spectroscopy. Lastly, a colony forming unit (CFU) count was performed following 24 h growth of S. mutans on 6 mm diameter resin disks with different light treatments of an LED device and a laser at 660 nm. The MIC results only showed a reduction in S. mutans at AuNP concentrations less than 3.12 µg/mL under a laser illumination level of 95.5 J/cm2 compared to the dark treatment (p < 0.010 for each). CFU and DC results showed no significant dependence on any light treatment studied. The AuNPs expressed antibacterial effects following PPT against planktonic S. mutans but not in a polymerized dental adhesive resin. Future studies should focus on different shapes, structure, and concentrations of AuNPs loaded in a resin blend.

Quantifying particle concentration via AI-enhanced optical coherence tomography

Efficient and robust quantification of the number of nanoparticles in solution is not only essential but also insufficient in nanotechnology and biomedical research. This paper proposes to use optical coherence tomography (OCT) to quantify the number of gold nanorods, which exemplify the nanoparticles with high light scattering signals. Additionally, we have developed an AI-enhanced OCT image processing to improve the accuracy and robustness of the quantification result.

Detection and photothermal inactivation of Gram-positive and Gram-negative bloodstream bacteria using photonic crystal biosensor and plasmonic core-shell

Plasmonics and core-shell nanomaterials hold great potential to develop pharmaceuticals and medical equipment due to their eco-friendly and cost effective fabrication procedures. Despite these advancements, combating drug-resistant bacterial infections remains a global challenge. Therefore, this study aims to introduce a tailored theoretical framework for a one-dimensional (1D) photonic crystal biosensor (PCB) composed of (ZrO2/GaN)N/defect layer/(ZrO2/GaN)N, designed to detect Gram-positive and Gram-negative bloodstream bacteria employing the transfer matrix method (TMM). In addition, using the finite difference methods (FDM), the photothermal inactivation of bloodstream bacteria with plasmonic core-shell structures (FeO@AuBiS2) was explored using key factors such as light absorption, heat generation, and thermal diffusion. By incorporating six dielectric layers and contaminated blood into the proposed PCB, a maximum sensitivity of 562 nm per RIU was recorded, and using rod-shaped plasmonic core-shell structures, 5.8 nm-1 light absorption capacity and 152 K change in temperature were achieved. The maximum detection sensitivity, light absorption, heat conduction and heat convection capacity of the proposed 1D PCB and plasmonic core-shell show an effective approach to combating drug-resistant bacteria.

Antibiotics Coupled with Photothermal Therapy for the Enhanced Killing of Bacteria

In this study, the application of ionic materials as a combination antibiotic drug was investigated. The fluoroquinolone, Norfloxacin, was converted into the ionic form and combined with the cationic dye, IR780+, using an ion-exchange reaction. The resulting ionic combination drug possesses two killing mechanisms in one compound. The antibiotic chemical mechanism along with the photothermal mechanism that was acquired by adding IR780 to the compound led to the development of a combination antibiotic drug. This ionic combination drug consisting of Norfloxacin anion and IR780 cation is easily dispersed in water using sonication waves. The parent compounds and ionic combination drug, dissolved in organic solvent and dispersed in water, were characterized, and the photophysical properties were studied in detail. It was discovered that the aqueous ionic combination drugs exhibited significant changes in absorbance and photoluminescent properties. In aqueous media, the dispersed ionic combination drug exhibited a very broad absorbance with an additional peak around 1000 nm which is advantageous in photothermal. A significant decrease in the quantum yield along with enhanced non-radiative rate constant was observed for the combination drug in the aqueous. The photothermal mechanism is present in both the parent IR780 dye and the ionic combination drug. The ionic combination drug displayed a high light-to-heat conversion efficiency and temperature increase similar to the parent dye. The combination of both killing mechanisms in the ionic combination drug resulted in enhanced antibacterial activity against Escherichia coli as compared to the parent Norfloxacin and IR780-I individually.

Multifactorial role of nanoparticles in alleviating environmental stresses for sustainable crop production and protection

In the era of dire environmental fluctuations, plants undergo several stressors during their life span, which severely impact their development and overall growth in negative aspects. Abiotic stress factors, especially moisture stress i.e shortage (drought) or excess (flooding), salinity, temperature divergence (i.e. heat and cold stress), heavy metal toxicity, etc. create osmotic and ionic imbalance inside the plant cells, which ultimately lead to devastating crop yield, sometimes crop failure. Apart from the array of abiotic stresses, various biotic stress caused by pathogens, insects, and nematodes also affect production. Therefore, to combat these major challenges in order to increase production, several novel strategies have been adapted, among which the use of nanoparticles (NPs) i.e. nanotechnology is becoming an emerging tool in various facets of the current agriculture system, nowadays. This present review will elaborately depict the deployment and mechanisms of different NPs to withstand these biotic and abiotic stresses, along with a brief overview and indication of the future research works to be oriented based on the steps provided for future research in advance NPs application through the sustainable way.

Antimicrobial peptides as drugs with double response against Mycobacterium tuberculosis coinfections in lung cancer

Tuberculosis and lung cancer are, in many cases, correlated diseases that can be confused because they have similar symptoms. Many meta-analyses have proven that there is a greater chance of developing lung cancer in patients who have active pulmonary tuberculosis. It is, therefore, important to monitor the patient for a long time after recovery and search for combined therapies that can treat both diseases, as well as face the great problem of drug resistance. Peptides are molecules derived from the breakdown of proteins, and the membranolytic class is already being studied. It has been proposed that these molecules destabilize cellular homeostasis, performing a dual antimicrobial and anticancer function and offering several possibilities of adaptation for adequate delivery and action. In this review, we focus on two important reason for the use of multifunctional peptides or peptides, namely the double activity and no harmful effects on humans. We review some of the main antimicrobial and anti-inflammatory bioactive peptides and highlight four that have anti-tuberculosis and anti-cancer activity, which may contribute to obtaining drugs with this dual functionality.

Optical, structural and antibacterial properties of silver nanoparticles and DNA-templated silver nanoclusters

Silver nanoparticles (AgNPs) are increasingly considered for biomedical applications as drug-delivery carriers, imaging probes and antibacterial agents. Silver nanoclusters (AgNCs) represent another subclass of nanoscale silver. AgNCs are a promising tool for nanomedicine due to their small size, structural homogeneity, antibacterial activity and fluorescence, which arises from their molecule-like electron configurations. The template-assisted synthesis of AgNCs relies on organic molecules that act as polydentate ligands. In particular, single-stranded nucleic acids reproducibly scaffold AgNCs to provide fluorescent, biocompatible materials that are incorporable in other formulations. This mini review outlines the design and characterization of AgNPs and DNA-templated AgNCs, discusses factors that affect their physicochemical and biological properties, and highlights applications of these materials as antibacterial agents and biosensors.

Light-related activities of metal-based nanoparticles and their implications on dermatological treatment

Metal-based nanoparticles (MNPs) represent an emerging class of materials that have attracted enormous attention in many fields. By comparison with other biomaterials, MNPs own unique optical properties which make them a potential alternative to conventional therapeutic agents in medical applications. Especially, owing to the easy access to the skin, the use of MNPs based on their optical properties has gained importance for the treatment of a variety of skin diseases. This review provides an insight into the different optical properties of MNPs, including photoprotection, photocatalysis, and photothermal, and highlights their implications in treating skin disorders, with a special emphasis on their use in infection control. Finally, a perspective on the safety concern of MNPs for dermatological use is discussed and analyzed. The information gathered and presented in this review will help the readers have a comprehensive understanding of utilizing the photo-triggered activity of MNPs for the treatment of skin diseases.

Time-resolved spectroscopic mapping of vibrational energy flow in proteins: Understanding thermal diffusion at the nanoscale

Vibrational energy exchange between various degrees of freedom is critical to barrier-crossing processes in proteins. Hemeproteins are well suited for studying vibrational energy exchange in proteins because the heme group is an efficient photothermal converter. The released energy by heme following photoexcitation shows migration in a protein moiety on a picosecond timescale, which is observed using time-resolved ultraviolet resonance Raman spectroscopy. The anti-Stokes ultraviolet resonance Raman intensity of a tryptophan residue is an excellent probe for the vibrational energy in proteins, allowing the mapping of energy flow with the spatial resolution of a single amino acid residue. This Perspective provides an overview of studies on vibrational energy flow in proteins, including future perspectives for both methodologies and applications.

CD24-gold nanocomposite as promising and sensitive biomarker for cancer stem cells in salivary gland tumors

Cancer stem cells are highly tumorigenic cells in the majority of the tumor that are responsible for the initiation, rapid growth, invasion, metastasis, and therapeutic resistance associated with various human cancers. The aim of this project is to assess a diagnostic and prognostic biomarker for the detection of cancer stem cells in salivary gland tumors using gold nanoparticles that are synthesized and conjugated to CD24 primer to form a CD24-Gold Nanocomposite. Sixty cases were included (29 pleomorphic adenoma, 19 carcinoma ex pleomorphic adenoma, and 12 normal controls). Alterations in biomarker expression between studied groups were analyzed and correlated with clinicopathological characteristics using Fisher's exact and Chi-square tests. ROC and Kaplan-Meier curves were used to validate diagnostic and prognostic values, respectively. This study confirms that CD24-Gold Nanocomposite served as a promising and highly sensitive biomarker in salivary gland tumor diagnosis and prognosis prediction.

Biologically Derived Gold Nanoparticles and Their Applications

Nanotechnology is a rapidly evolving discipline as it has a wide variety of applications in several fields. They have been synthesized in a variety of ways. Traditional processes such as chemical and physical synthesis have limits, whether in the form of chemical contamination during synthesis operations or in subsequent applications and usage of more energy. Over the last decade, research has focused on establishing easy, nontoxic, clean, cost-effective, and environmentally friendly techniques for nanoparticle production. To achieve this goal, biological synthesis was created to close this gap. Biosynthesis of nanoparticles is a one-step process, and it is ecofriendly in nature. The metabolic activities of biological agents convert dissolved metal ions into nanometals. For biosynthesis of metal nanoparticles, various biological agents like plants, fungus, and bacteria are utilized. In this review paper, the aim is to provide a summary of contemporary research on the biosynthesis of gold nanoparticles and their applications in various domains have been discussed.

Mild Hyperthermia Induced by Hollow Mesoporous Prussian Blue Nanoparticles in Alliance with a Low Concentration of Hydrogen Peroxide Shows Powerful Antibacterial Effect

The emergence of superbacteria as well as the drug resistance of the current bacteria gives rise to worry regarding a bacterial pandemic and also calls for the development of novel ways to combat the bacteria. Here in this article, we demonstrate that mild hyperthermia induced by hollow mesoporous Prussian blue nanoparticles (HMPBNPs) in alliance with a low concentration of hydrogen peroxide (H₂O₂) shows a powerful inhibition effect on bacteria. Our results demonstrate that this therapeutic regime could realize almost full growth inhibition of both Gram-positive (Staphylococcus aureus, S. aureus) and -negative bacteria (Escherichia coli, E. coli), as well as potent inhibition/elimination of the S. aureus biofilm. The wound healing results indicate that combination regime of the antibacterial system could be conveniently used for wound disinfection in vivo and could promote wound healing. To our limited knowledge, this is one of the few pioneer works to apply mild hyperthermia for the combat of bacteria, which provides a novel strategy to inspire future studies.

Organic Photo-antimicrobials: Principles, Molecule Design, and Applications

The emergence of multi-drug-resistant pathogens threatens the healthcare systems world-wide. Recent advances in phototherapy (PT) approaches mediated by photo-antimicrobials (PAMs) provide new opportunities for the current serious antibiotic resistance. During the PT treatment, reactive oxygen species or heat produced by PAMs would react with the cell membrane, consequently leaking cytoplasm components and effectively eradicating different pathogens like bacteria, fungi, viruses, and even parasites. This Perspective will concentrate on the development of different organic photo-antimicrobials (OPAMs) and their application as practical therapeutic agents into therapy for local infections, wound dressings, and removal of biofilms from medical devices. We also discuss how to design highly efficient OPAMs by modifying the chemical structure or conjugating with a targeting component. Moreover, this Perspective provides a discussion of the general challenges and direction for OPAMs and what further needs to be done. It is hoped that through this overview, OPAMs can prosper and will be more widely used for microbial infections in the future, especially at a time when the global COVID-19 epidemic is getting more serious.

Conjugated Organic Photothermal Films for Spatiotemporal Thermal Engineering

With the growth of photoenergy harvesting and thermal engineering, photothermal materials (PTMs) have attracted substantial interest due to their unique functions such as localized heat generation, spatiotemporal thermal controllability, invisibility, and light harvesting capabilities. In particular, π-conjugated organic PTMs show advantages over inorganic or metallic PTMs in thin film applications due to their large light absorptivity, ease of synthesis and tunability of molecular structures for realizing high NIR absorption, flexibility, and solution processability. This review is intended to provide an overview of organic PTMs, including both molecular and polymeric PTMs. A description of the photothermal (PT) effect and conversion efficiency (ηPT ) for organic films is provided. After that, the chemical structure and optical properties of organic PTMs are discussed. Finally, emerging applications of organic PT films from the perspective of spatiotemporal thermal engineering principles are illustrated.

Plasmonic Gold Nanoparticles (AuNPs): Properties, Synthesis and their Advanced Energy, Environmental and Biomedical Applications

Inducing plasmonic characteristics, primarily localized surface plasmon resonance (LSPR), in conventional AuNPs through particle size and shape control could lead to a significant enhancement in electrical, electrochemical, and optical properties. Synthetic protocols and versatile fabrication methods play pivotal roles to produced plasmonic gold nanoparticles (AuNPs), which can be employed in multipurpose energy, environmental and biomedical applications. The main focus of this review is to provide a comprehensive and tutorial overview of various synthetic methods to design highly plasmonic AuNPs, along with a brief essay to understand the experimental procedure for each technique. The latter part of the review is dedicated to the most advanced and recent solar-induced energy, environmental and biomedical applications. The synthesis methods are compared to identify the best possible synthetic route, which can be adopted while employing plasmonic AuNPs for a specific application. The tutorial nature of the review would be helpful not only for expert researchers but also for novices in the field of nanomaterial synthesis and utilization of plasmonic nanomaterials in various industries and technologies.

Gold Nanomaterial Engineering for Macrophage-Mediated Inflammation and Tumor Treatment

Macrophages play an important role in the body's immune defense process. Phenotype imbalance between M1 and M2 macrophages induced by inflammation-related disorders and tumor can also be reversibly converted to treat these diseases. As exogenous substances, a large part of gold-based nanomaterials interact with macrophages once they enter the body, which provides gold nanomaterials a huge advantage to act as imaging contrasts, active substance carriers, and therapeutic agents for macrophage modulation. By cutting off macrophage recruitment, inhibiting macrophage activities, and modulating M1/M2 polarization, gold nanomaterial engineering exerts therapeutic effects on inflammation-related diseases at target sites. In this review, biological functions of macrophages in inflammation-related diseases are introduced, the effect of physicochemical factors of gold nanomaterials including size, shape, and surface chemistry is focused on the interaction between macrophages and gold nanomaterials, and the applications of gold nanomaterials are elaborated for tracking and treating these diseases by macrophages. The rational and smart engineering of gold nanomaterials allows a promising platform for macrophage-mediated inflammation and tumor imaging and treatment.

Plasmonically Modulated Gold Nanostructures for Photothermal Ablation of Bacteria

With the wide utilization of antibiotics, antibiotic-resistant bacteria have been often developed more frequently to cause potential global catastrophic consequences. Emerging photothermal ablation has been attracting extensive research interest for quick/effective eradication of pathogenic bacteria from contaminated surroundings and infected body. In this field, anisotropic gold nanostructures with tunable size/morphologies have been demonstrated to exhibit their outstanding photothermal performance through strong plasmonic absorption of near-infrared (NIR) light, efficient light to heat conversion, and easy surface modification for targeting bacteria. To this end, this review first introduces thermal treatment of infectious diseases followed by photothermal therapy via heat generation on NIR-absorbing gold nanostructures. Then, the usual synthesis and spectral features of diversified gold nanostructures and composites are systematically overviewed with the emphasis on the importance of size, shape, and composition to achieve strong plasmonic absorption in NIR region. Further, the innovated photothermal applications of gold nanostructures are comprehensively demonstrated to combat against bacterial infections, and some constructive suggestions are also discussed to improve photothermal technologies for practical applications.

Recent advances in functionalized nanomaterials for the diagnosis and treatment of bacterial infections

The growing problem of resistant infections due to antibiotic misuse is a worldwide concern that poses a grave threat to healthcare systems. Thus, it is necessary to discover new strategies to combat infectious diseases. In this review, we provide a selective overview of recent advances in the use of nanocomposites as alternatives to antibiotics in antimicrobial treatments. Metals and metal oxide nanoparticles (NPs) have been associated with inorganic and organic supports to improve their antibacterial activity and stability as well as other properties. For successful antibiotic treatment, it is critical to achieve a high drug concentration at the infection site. In recent years, the development of stimuli-responsive systems has allowed the vectorization of antibiotics to the site of infection. These nanomaterials can be triggered by various mechanisms (such as changes in pH, light, magnetic fields, and the presence of bacterial enzymes); additionally, they can improve antibacterial efficacy and reduce side effects and microbial resistance. To this end, various types of modified polymers, lipids, and inorganic components (such as metals, silica, and graphene) have been developed. Applications of these nanocomposites in diverse fields ranging from food packaging, environment, and biomedical antimicrobial treatments to diagnosis and theranosis are discussed.

Comparison study on the effect of gold nanoparticles shape in the forms of star, hallow, cage, rods, and Si-Au and Fe-Au core-shell on photothermal cancer treatment

Gold nanoparticles (GNPs) indicate potential in the development of cancer treatments as vehicles for thermal damage of cancer cells because of their photothermal heating capability. Herein, we aim to investigate the effect of GNPs geometry as photothermal transducers on cellular uptake and photothermal therapy (PTT) efficacy. For this aim, seven different shapes of anisotropic GNPs: stars, hollow, rods, cages, spheres, Fe-Au, and Si-Au core shells were synthesized and investigate the effect of shape on GNPs optical properties. The physic-chemical characterization of prepared GNPs was investigated by UV-vis, DLS-Zeta, and TEM analysis. The effect of GNPs geometry on cellular uptake was investigated by ICP-MS and flow cytometry method. The PTT potential of these GNPs was compared on MCF7 cells in vitro using MTT assay, cell cycle, and Annexin-V apoptosis assay. While all these GNPs could absorb and convert near-infrared light into heat, gold nanostars exhibited the lowest cytotoxicity, highest cellular uptake and highest heat generation compared to other structures. Following photothermal treatment, due to substantial heat production in MCF7 cells, the apoptosis induction rate was greatly increased for all anisotropic gold nanostructures (stars, hollow, rods, and cages) especially gold nanostars. Combined, we can conclude that GNPs geometry affects cellular uptake and heat generation amount as well as cell destruction by apoptosis pathway. The gold nanostar is promising candidates for photothermal destruction.

Quantum Leap from Gold and Silver to Aluminum Nanoplasmonics for Enhanced Biomedical Applications

Nanotechnology has been used in many biosensing and medical applications, in the form of noble metal (gold and silver) nanoparticles and nanostructured substrates. However, the translational clinical and industrial applications still need improvements of the efficiency, selectivity, cost, toxicity, reproducibility, and morphological control at the nanoscale level. In this review, we highlight the recent progress that has been made in the replacement of expensive gold and silver metals with the less expensive aluminum. In addition to low cost, other advantages of the aluminum plasmonic nanostructures include a broad spectral range from deep UV to near IR, providing additional signal enhancement and treatment mechanisms. New synergistic treatments of bacterial infections, cancer, and coronaviruses are envisioned. Coupling with gain media and quantum optical effects improve the performance of the aluminum nanostructures beyond gold and silver.

Smart, Photothermally Activated, Antibacterial Surfaces with Thermally Triggered Bacteria-Releasing Properties

The development of effective antibacterial surfaces to prevent the attachment of pathogenic bacteria and subsequent bacterial colonization and biofilm formation is critically important for medical devices and public hygiene products. In the work reported herein, a smart antibacterial hybrid film based on tannic acid/Fe³⁺ ion (TA/Fe) complex and poly(N-isopropylacrylamide) (PNIPAAm) is deposited on diverse substrates. This surface is shown to have bacteria-killing and bacteria-releasing properties based on, respectively, near-infrared photothermal activation and subsequent cooling. The TA/Fe complex has three roles in this system: (i) as a universal adhesive "anchor" for surface modification, (ii) as a high-efficiency photothermal agent for ablation of attached bacteria (including multidrug resistant bacteria), and (iii) as a robust linker for immobilization of NH₂-terminated PNIPAAm via either Michael addition or Schiff base formation. Moreover, because of the thermoresponsive properties of the immobilized PNIPAAm, almost all of the killed bacteria and other debris can be removed from the surface simply by lowering the temperature. It is shown that this hybrid film can maintain good antibacterial performance after being used for multiple "kill-and-release" cycles and can be applied to various substrates regardless of surface chemistry or topography, thus providing a broadly applicable, simple, and reliable solution to the problems associated with surface-attached bacteria in various healthcare applications.

Single-particle Correlation Study: Polarization-dependent Differential Interference Contrast Imaging of Two-dimensional Gold Nanoplates

Questions surrounding the optical properties of two-dimensional (2D) triangular single gold nanoplates (AuNPs) remain largely unanswered. Herein, a scanning-electron microscopy-correlated single-particle study was conducted to identify polarization-dependent optical properties of AuNPs under dark-field (DF) and differential interference contrast (DIC) microscopy. AuNPs with an aspect ratio of ∼3 showed a single broad DF scattering spectrum without separation of the two dipole and quadrupole resonance modes present in 2D AuNPs. Polarization-sensitive interference properties of the individual AuNPs were revealed through periodic changes in the intensities and types of DIC images obtained. A dipole resonance mode was found to mainly contribute to the polarization-sensitive interference properties of AuNPs. Furthermore, DIC polarization anisotropy allowed us to track the real-time orientation of a dipole resonance mode of a AuNP rotating on a live cell membrane.

Photothermal-Induced Antibacterial Activity of Gold Nanorods Loaded into Polymeric Hydrogel against Pseudomonas aeruginosa Biofilm

In this study, the photothermal-induced bactericidal activity of phospholipid-decorated gold nanorods (DSPE-AuNR) suspension against Pseudomonas aeruginosa planktonic and biofilm cultures was investigated. We found that the treatment of planktonic culture of Pseudomonas aeruginosa with DSPE-AuNR suspension (0.25-0.03 nM) followed by a continuous laser beam exposure resulted in ~6 log cycle reduction of the bacterial viable count in comparison to the control. The percentage reduction of Pseudomonas aeruginosa biofilm viable count was ~2.5-6.0 log cycle upon laser excitation with different concentrations of DSPE-AuNR as compared to the control. The photothermal ablation activity of DSPE-AuNR (0.125 nM) loaded into poloxamer 407 hydrogel against Pseudomonas aeruginosa biofilm resulted in ~4.5-5 log cycle reduction in the biofilm viable count compared to the control. Moreover, transmission electron microscope (TEM) images of the photothermally-treated bacteria revealed a significant change in the bacterial shape and lysis of the bacterial cell membrane in comparison to the untreated bacteria. Furthermore, the results revealed that continuous and pulse laser beam modes effected a comparable photothermal-induced bactericidal activity. Therefore, it can be concluded that phospholipid-coated gold nanorods present a promising nanoplatform to eradicate Pseudomonas aeruginosa biofilm responsible for common skin diseases.

Encapsulation of Gold Nanorods with Porphyrins for the Potential Treatment of Cancer and Bacterial Diseases: A Critical Review

Cancer and bacterial diseases have been the most incidental diseases to date. According to the World Health Report 2018, at least every family is affected by cancer around the world. In 2012, 14.1 million people were affected by cancer, and that figure is bound to increase to 21.6 million in 2030. Medicine therefore sorts out ways of treatment using conventional methods which have been proven to have many side effects. Researchers developed photothermal and photodynamic methods to treat both cancer and bacterial diseases. These methods pose fewer effects on the biological systems but still no perfect method has been synthesized. The review serves to explore porphyrin and gold nanorods to be used in the treatment of cancer and bacterial diseases: porphyrins as photosensitizers and gold nanorods as delivery agents. In addition, the review delves into ways of incorporating photothermal and photodynamic therapy aimed at producing a less toxic, more efficacious, and specific compound for the treatment.

Responsive and Synergistic Antibacterial Coatings: Fighting against Bacteria in a Smart and Effective Way

Antibacterial coatings that eliminate initial bacterial attachment and prevent subsequent biofilm formation are essential in a number of applications, especially implanted medical devices. Although various approaches, including bacteria-repelling and bacteria-killing mechanisms, have been developed, none of them have been entirely successful due to their inherent drawbacks. In recent years, antibacterial coatings that are responsive to the bacterial microenvironment, that possess two or more killing mechanisms, or that have triggered-cleaning capability have emerged as promising solutions for bacterial infection and contamination problems. This review focuses on recent progress on three types of such responsive and synergistic antibacterial coatings, including i) self-defensive antibacterial coatings, which can "turn on" biocidal activity in response to a bacteria-containing microenvironment; ii) synergistic antibacterial coatings, which possess two or more killing mechanisms that interact synergistically to reinforce each other; and iii) smart "kill-and-release" antibacterial coatings, which can switch functionality between bacteria killing and bacteria releasing under a proper stimulus. The design principles and potential applications of these coatings are discussed and a brief perspective on remaining challenges and future research directions is presented.

Sulfhydryl functionalized graphene oxide for efficient preconcentration and photoablation of pathogenic bacteria

Sulfhydryl functionalized graphene oxide was synthesized for efficient preconcentration and photoablation of pathogenic bacteria.

High fidelity visualization of multiscale dynamics of laser-induced bubbles in liquids containing gold nanoparticles

Cavitation in pure liquids and in liquids containing nanoparticles enables applications in mechanics, bio-medicine, and energy. Its evolution carries a significant interest. We describe the multiscale dynamic evolution of ultrafast-laser-induced cavitation in pure and gold-nanoparticles-doped liquids in one-dimensional geometries induced by non-diffractive ultrashort Bessel-Gauss laser beams. Covering the complete electronic and thermomechanical cycle, from the early plasma phase to bubble cavitation and collapse on ms timescales, we reconstitute, using time-resolved imaging with amplitude and phase sensitivity, the hydrodynamic phenomena concurring to bubble evolution. We indicate geometry-specific instabilities accompanying the collapse. The insertion of gold nanoparticles of 200 nm size has subtle effects in the process energetics. Albeit a moderate field enhancement minimizing the contribution to breakdown, the nanoparticles play a role in the overall relaxation dynamics of bubbles. The evolving bubble border in nanoparticles-containing liquids create a snow-plough effect that sweeps the nanoparticles at the gas liquid interface. This indicates that during the macroscopic cavity development, the nanoparticles were removed from the interaction region and dragged by the hydrodynamic movement. We thus shed light on the evolution of cavitation bubbles not triggered but perturbed by the presence of nanoparticles.

Regenerable smart antibacterial surfaces: full removal of killed bacteria via a sequential degradable layer

An antibiotic-free and regenerable antibacterial hybrid film with both photothermal bactericidal activity and bacteria-releasing properties is fabricated on diverse substrates.

Multifunctional bacterial imaging and therapy systems

Advanced antibacterial materials are classified and introduced, and their applications in multimodal imaging and therapy are reviewed.

Recent progress in theranostic applications of hybrid gold nanoparticles

A significant area of research is theranostic applications of nanoparticles, which involves efforts to improve delivery and reduce side effects. Accordingly, the introduction of a safe, effective, and, most importantly, renewable strategy to target, deliver and image disease cells is important. This state-of-the-art review focuses on studies done from 2013 to 2016 regarding the development of hybrid gold nanoparticles as theranostic agents in the diagnosis and treatment of cancer and infectious disease. Several syntheses (chemical and green) methods of gold nanoparticles and their applications in imaging, targeting, and delivery are reviewed; their photothermal efficiency is discussed as is the toxicity of gold nanoparticles. Owing to the unique characterizations of hybrid gold nanoparticles and their potential to be developed as multifunctional, we predict they will present an undeniable role in clinical studies and provide treatment platforms for various diseases. Thus, their clearance and interactions with extra- and intra-cellular molecules need to be considered in future projects.

Chemo-photothermal therapy of cancer cells using gold nanorod-cored stimuli-responsive triblock copolymer

The combination of photothermal therapy and chemotherapy, when carefully planned, has been shown to be an effective cancer treatment option clinically and preclinically.