Self-assembled ordered AuNRs-modified electrodes for simultaneous determination of dopamine and topotecan with improved data reproducibility.

Gold nanomaterials have been widely explored in electrochemical sensors due to their high catalytic property and good stability in multi-medium. In this paper, the reproducibility of the signal among batches of gold nanorods (AuNRs)-modified electrodes was investigated to improve the data stabilization and repeatability. Ordered and random self-assembled AuNRs-modified electrodes were used as electrochemical sensors for the simultaneous determination of dopamine (DA) and topotecan (TPC), with the aim of obtaining an improved signal stability in batches of electrodes and realizing the simultaneous determination of both substances. The morphology and structure of the assemblies were analyzed and characterized by UV-Vis spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray powder diffraction (XRD). Electrochemical studies showed that the ordered AuNRs/ITO electrodes have excellent signal reproducibility among several individuals due to the homogeneous mass transfer in the ordered arrangement of the AuNRs. Under the optimized conditions, the simultaneous detection results of DA and TPC showed good linearity in the ranges 1.75-45 µM and 1.5-40 µM, and the detection limits of DA and TPC were 0.06 µM and 0.17 µM, respectively. The results showed that the prepared ordered AuNR/ITO electrode had high sensitivity, long-term stability, and reproducibility for the simultaneous determination of DA and TPC, and it was expected to be applicable for real sample testing.

Mitochondrial transfer in tunneling nanotubes-a new target for cancer therapy.

A century ago, the Warburg effect was first proposed, revealing that cancer cells predominantly rely on glycolysis during the process of tumorigenesis, even in the presence of abundant oxygen, shifting the main pathway of energy metabolism from the tricarboxylic acid cycle to aerobic glycolysis. Recent studies have unveiled the dynamic transfer of mitochondria within the tumor microenvironment, not only between tumor cells but also between tumor cells and stromal cells, immune cells, and others. In this review, we explore the pathways and mechanisms of mitochondrial transfer within the tumor microenvironment, as well as how these transfer activities promote tumor aggressiveness, chemotherapy resistance, and immune evasion. Further, we discuss the research progress and potential clinical significance targeting these phenomena. We also highlight the therapeutic potential of targeting intercellular mitochondrial transfer as a future anti-cancer strategy and enhancing cell-mediated immunotherapy.

Direct interaction between marine cyanobacteria mediated by nanotubes.

Microbial associations and interactions drive and regulate nutrient fluxes in the ocean. However, physical contact between cells of marine cyanobacteria has not been studied thus far. Here, we show a mechanism of direct interaction between the marine cyanobacteria Prochlorococcus and Synechococcus, the intercellular membrane nanotubes. We present evidence of inter- and intra-genus exchange of cytoplasmic material between neighboring and distant cells of cyanobacteria mediated by nanotubes. We visualized and measured these structures in xenic and axenic cultures and in natural samples. We show that nanotubes are produced between living cells, suggesting that this is a relevant system of exchange material in vivo. The discovery of nanotubes acting as exchange bridges in the most abundant photosynthetic organisms in the ocean may have important implications for their interactions with other organisms and their population dynamics.

Integrating Photoelectrochemical Feature on a Hydrovoltaic Chip with High-Salinity Adaption as a Self-Powered Device for Formaldehyde Monitoring.

Alternative energy sources are required due to the decline in fossil fuel resources. Therefore, devices that utilize hydrovoltaic technology and light energy have drawn widespread attention because they are emission-free and solar energy is inexhaustible. However, previous investigations mainly focused on accelerating the water evaporation rate at the electrode interface. Here, a cooperative photoelectrochemical effect on a hydrovoltaic chip is achieved using NH2-MIL-125-modified TiO2 nanotube arrays (NTs). This device demonstrated significantly improved evaporation-triggered electricity generation. Under LED illumination, the open-circuit voltage (VOC) of the NH2-MIL-125/TiO2NTs active layer of the hydrovoltaic chip was enhanced by 90.3% (up to 400.2 mV). Furthermore, the prepared hydrovoltaic chip showed good high-salinity tolerance, maintaining 74.6% of its performance even in 5 M NaCl. By introducing a Schiff-based reaction between the active layer and formaldehyde, a fully integrated flexible sensor was successfully fabricated for formaldehyde monitoring, and a low limit of detection of 5.2 × 10-9 M was achieved. This novel strategy for improving the performance of hydrovoltaic devices offers a completely new general approach to construct self-powered devices for point-of-care sensing.

Gold Nanorod-Loaded Nano-Contrast Agent with Composite Shell-Core Structure for Ultrasonic/Photothermal Imaging-Guided Therapy in Ischemic Muscle Disorders.

Purpose: This study aims to broaden the application of nano-contrast agents (NCAs) within the realm of the musculoskeletal system. It aims to introduce novel methods, strategies, and insights for the clinical management of ischemic muscle disorders, encompassing diagnosis, monitoring, evaluation, and therapeutic intervention. Methods: We developed a composite encapsulation technique employing O-carboxymethyl chitosan (OCMC) and liposome to encapsulate NCA-containing gold nanorods (GNRs) and perfluoropentane (PFP). This nanoscale contrast agent was thoroughly characterized for its basic physicochemical properties and performance. Its capabilities for in vivo and in vitro ultrasound imaging and photothermal imaging were authenticated, alongside a comprehensive biocompatibility assessment to ascertain its effects on microcirculatory perfusion in skeletal muscle using a murine model of hindlimb ischemia, and its potential to augment blood flow and facilitate recovery. Results: The engineered GNR@OCMC-liposome/PFP nanostructure exhibited an average size of 203.18±1.49 nm, characterized by size uniformity, regular morphology, and a good biocompatibility profile. In vitro assessments revealed NCA's potent photothermal response and its transformation into microbubbles (MBs) under near-infrared (NIR) irradiation, thereby enhancing ultrasonographic visibility. Animal studies demonstrated the nanostructure's efficacy in photothermal imaging at ischemic loci in mouse hindlimbs, where NIR irradiation induced rapid temperature increases and significantly increased blood circulation. Conclusion: The dual-modal ultrasound/photothermal NCA, encapsulating GNR and PFP within a composite shell-core architecture, was synthesized successfully. It demonstrated exceptional stability, biocompatibility, and phase transition efficiency. Importantly, it facilitates the encapsulation of PFP, enabling both enhanced ultrasound imaging and photothermal imaging following NIR light exposure. This advancement provides a critical step towards the integrated diagnosis and treatment of ischemic muscle diseases, signifying a pivotal development in nanomedicine for musculoskeletal therapeutics.

Homochiral light-sensitive metal-organic framework photoelectrochemical gated transistor for enantioselective discrimination of monosaccharides.

As pure antipodes may differ in biological interactions, pharmacology, and toxicity, discrimination of enantiomers is important in the pharmaceutical and agrochemical industries. Two major challenges in enantiomer determination are transducing and amplifying the distinct chiral-recognition signals. In this study, a light-sensitive organic photoelectrochemical transistor (OPECT) with homochiral character is developed for enantiomer discrimination. Demonstrated with the discrimination of glucose enantiomers, the photoelectrochemically active gate electrode is prepared by integrating Au nanoparticles (AuNPs) and a chiral Cu(II)-metal-organic framework (c-CuMOF) onto TiO2 nanotube arrays (TNT). The captured glucose enantiomers are oxidized to hydrogen peroxide (H2O2) by the oxidase-mimicking AuNPs-loaded c-CuMOF. Based on the confinement effect of the mesopocket structure of the c-CuMOF and the remarkable charge transfer ability of the 1D nanotubular architecture, variations in H2O2 yield are translated into significant changes in OPECT drain currents (ID) by inducing a catalytic precipitation reaction. Variations in ID confer a sensitive discrimination of glucose enantiomers with a limit of detection (LOD) of 0.07 µM for L-Glu and 0.05 µM for D-Glu. This enantiomer-driven gate electrode response strategy not only provides a new route for enantiomer identification, but also helps to understand the origin of the high stereoselectivity in living systems.

Unraveling the structure-chirality sensing relationship between achiral anthracene-based tetracationic nanotubes and nucleosides in aqueous host-guest complexation.

In biological systems, nucleosides play crucial roles in various physiological processes. In this study, we designed and synthesized four achiral anthracene-based tetracationic nanotubes (1-4) as artificial hosts and chiroptical sensors for nucleosides in aqueous media. Notably, different nanotubes exhibit varied chirality sensing on circular dichroism (CD)/circularly polarized luminescence (CPL) spectra through the host-guest complexation, which prompted us to explore the factors influencing their chiroptical responses. Through systematic host-guest experiments, the structure-chirality sensing relationship between achiral anthracene-based tetracationic nanotubes and nucleosides in the host-guest complexation was unraveled. Firstly, the CD response originates from the anthracene rings situated at the side-wall position, resulting from the right-handed (P)- or left-handed (M)-twisted conformation of the macrocyclic structure. Secondly, the CPL signal is influenced by the presence of anthracene rings at the linking-wall position, which results from intermolecular chiral twisted stacking between these anthracene rings. Therefore, these nanotubes can serve as chiroptical sensor arrays to enhance the accuracy of nucleotide recognition through principal component analysis (PCA) analysis based on the diversified CD spectra. This study provides insights for the construction of adaptive chirality from achiral nanotubes with dynamic conformational nature and might facilitate further design of chiral functional materials for several applications.

Synergistic enhancement of wearable biosensor through Pt single-atom catalyst for sweat analysis.

Real-time monitoring of biological markers in sweat is a valuable tool for health assessment. In this study, we have developed an innovative wearable biosensor for precise analysis of glucose in sweat during physical activities. The sensor is based on a single-atom catalyst of platinum (Pt) uniformly dispersed on tricobalt tetroxide (Co3O4) nanorods and reduced graphene oxide (rGO), featuring a unique three-dimensional nanostructure and excellent glucose electrocatalytic performance with a wide detection range of 1-800 µM. Additionally, density functional theory calculations have revealed the synergetic role of Pt active sites in the Pt single-atom catalyst (Co3O4/rGO/Pt) in glucose adsorption and electron transfer, thereby enhancing sensor performance. To enable application in wearable devices, we designed an S-shaped microfluidic chip and a point-of-care testing (POCT) device, both of which were validated for effectiveness through actual use by volunteers. This research provides valuable insights and innovative approaches for analyzing sweat glucose using wearable devices, contributing to the advancement of personalized healthcare.

Metal-Organic Framework-Capped Gold Nanorod Hybrids for Combinatorial Cancer Therapy.

Recently, nanomaterials have attracted extensive attention in cancer-targeting therapy and as drug delivery vehicles owing to their unique surface and size properties. Multifunctional combinations of nanomaterials have become a research hotspot as researchers aim to provide a full understanding of their nanomaterial characteristics. In this study, metal-organic framework-capped gold nanorod hybrids were synthesized. Our research explored their ability to kill tumor cells by locally increasing the temperature via photothermal conclusion. The specific peroxidase-like activity endows the hybrids with the ability to disrupt the oxidative balance in vitro. Simultaneously, chemotherapeutic drugs are administered and delivered by loading and transportation for effective combinatorial cancer treatment, thereby enhancing the curative effect and reducing the unpredictable toxicity and side effects of large doses of chemotherapeutic drugs. These studies can improve combinatorial cancer therapy and enhance cancer treatment.

Comparison of Synthetic Pathways for Obtaining Fluorescent Nanomaterials Based on Halloysite and Carbon Dots for Potential Biological Sensing.

Recently, fluorescent sensors have gained considerable attention due to their high sensitivity, low cost and noninvasiveness. Among the different materials that can be used for this purpose, carbon dots (CDs) represent valuable candidates for applications in sensing. These, indeed, are easily synthesized, show high quantum yield and are highly biocompatible. However, it was pointed out that the photoluminescence properties of these nanomaterials are strictly dependent on the synthetic and purification methods adopted. The presence of halloysite nanotubes (HNTs), a natural, low cost and biocompatible clay mineral, has been found to be efficient in obtaining small and highly monodispersed CDs without long and tedious purification techniques. Herein, we report the comparison of synthetic pathways for obtaining halloysite-N-doped CDs (HNTs-NCDs) that could be used in biological sensing. One was based on the synthesis of N-doped CDs by a bottom-up approach on HNTs' surface by a MW pyrolysis process; the other one was based on the post-modification of pristine N-doped CDs with halloysite derivatives. The evaluation of the best synthetic route was performed by different physico-chemical techniques. It was found that the bottom-up approach led to the formation of N-doped CDs with different functional groups onto the HNTs' surface. This evidence was also translated in the different fluorescence quantum yields and the existence of several functional groups in the obtained materials was investigated by potentiometric titrations. Furthermore, the ability of the synthesized nanomaterials as sensors for Fe3+ ions detection was assessed by spectroscopic measurements, and the cellular uptake was verified by confocal/fluorescence microscopies as well.

An oleanic acid decorated gold nanorod for highly efficient inhibition of hemagglutinin and visible rapid detection of the influenza virus.

Accurate diagnosis and effective antiviral treatments are urgently needed for the prevention and control of flu caused by influenza viruses. In this study, a novel oleanic acid (OA) functionalized gold nanorod OA-AuNP was prepared through a convenient ligand-exchange reaction. As hemagglutinin (HA) on the viral surface binds strongly to the multiple OA molecules on the surface of the nanoparticle, the prepared OA-AuNP was found to exhibit potent antiviral activity against a wide range of influenza A virus strains. Furthermore, the change in color resulting from the specific binding between HA and OA and the resultant aggregation of the OA-AuNP can be visually observed or measured by UV-vis spectra with a detection limit of 2 and 0.18 hemagglutination units (HAU), respectively, which is comparable to the commercially available influenza colloid gold rapid diagnostic kits. These findings demonstrate the potential of the OA-AuNP for the development of novel multivalent antiviral conjugates and the diagnosis of influenza virus.

Nonclassical crystallization of goethite nanorods in limpet teeth by self-assembly of silica-rich nanoparticles reveals structure-mechanical property relations.

The intricate organization of goethite nanorods within a silica-rich matrix makes limpet teeth the strongest known natural material. However, the mineralization pathway of goethite in organisms under ambient conditions remains elusive. Here, by investigating the multi-level structure of limpet teeth at different growth stages, it is revealed that the growth of goethite crystals proceeds by the attachment of amorphous nanoparticles, a nonclassical crystallization pathway widely observed during the formation of calcium-based biominerals. Importantly, these nanoparticles contain a high amount of silica, which is gradually expelled during the growth of goethite. Moreover, in mature teeth of limpet, the content of silica correlates with the size of goethite crystals, where smaller goethite crystals are densely packed in the leading part with higher content of silica. Correspondingly, the leading part exhibits higher hardness and elastic modulus. Thus, this study not only reveals the nonclassical crystallization pathway of goethite nanorods in limpet teeth, but also highlights the critical roles of silica in controlling the hierarchical structure and the mechanical properties of limpet teeth, thus providing inspirations for fabricating biomimetic materials with excellent properties.

Emergence of a short peptide based reductase via activation of the model hydride rich cofactor.

In extant biology, large and complex enzymes employ low molecular weight cofactors such as dihydronicotinamides as efficient hydride transfer agents and electron carriers for the regulation of critical metabolic processes. In absence of complex contemporary enzymes, these molecular cofactors are generally inefficient to facilitate any reactions on their own. Herein, we report short peptide-based amyloid nanotubes featuring exposed arrays of cationic and hydrophobic residues that can bind small molecular weak hydride transfer agents (NaBH4) to facilitate efficient reduction of ester substrates in water. In addition, the paracrystalline amyloid phases loaded with borohydrides demonstrate recyclability, substrate selectivity and controlled reduction and surpass the capabilities of standard reducing agent such as LiAlH4. The amyloid microphases and their collaboration with small molecular cofactors foreshadow the important roles that short peptide-based assemblies might have played in the emergence of protometabolism and biopolymer evolution in prebiotic earth.

NIR-Responsive Methotrexate-Modified Iron Selenide Nanorods for Synergistic Magnetic Hyperthermic, Photothermal, and Chemodynamic Therapy.

Breast cancer is a malignant tumor with a high mortality rate among women. Therefore, it is necessary to develop novel therapies to effectively treat this disease. In this study, iron selenide nanorods (FeSe2 NRs) were designed for use in magnetic hyperthermic, photothermal, and chemodynamic therapy (MHT/PTT/CDT) for breast cancer. To illustrate their efficacy, FeSe2 NRs were modified with the chemotherapeutic agent methotrexate (MTX). MTX-modified FeSe2 (FeSe2-MTX) exhibited excellent controlled drug release properties. Fe2+ released from FeSe2 NRs induced the release of •OH from H2O2 via a Fenton/Fenton-like reaction, enhancing the efficacy of CDT. Under alternating magnetic field (AMF) stimulation and 808 nm laser irradiation, FeSe2-MTX exerted potent hyperthermic and photothermal effects by suppressing tumor growth in a breast cancer nude mouse model. In addition, FeSe2 NRs can be used for magnetic resonance imaging in vivo by incorporating their superparamagnetic characteristics into a single nanomaterial. Overall, we presented a novel technique for the precise delivery of functional nanosystems to tumors that can enhance the efficacy of breast cancer treatment.

A Hybrid Nanotube Stamp System in Intracellular Protein Delivery for Cancer Treatment and NMR Analytical Techniques.

In contrast to intracellular gene transfer, the direct delivery of expressed proteins is a significantly challenging yet essential technique for elucidating cellular functions, including protein complex structure, liquid-liquid phase separation, therapeutic applications, and reprogramming. In this study, we developed a hybrid nanotube (HyNT) stamp system that physically inserts the HyNTs into adhesive cells, enabling the injection of target molecules through HyNT ducts. This system demonstrates the capability to deliver multiple proteins, such as lactate oxidase (LOx) and ubiquitin (UQ), to approximately 1.8 × 107 adhesive cells with a delivery efficiency of 89.9% and a viability of 97.1%. The delivery of LOx enzyme into HeLa cancer cells induced cell death, while enzyme-delivered healthy cells remained viable. Furthermore, our stamp system can deliver an isotope-labeled UQ into adhesive cells for detection by nuclear magnetic resonance (NMR).

Halloysite nanotubes-based hybrid silica monolithic spin tip for hydrophilic solid-phase extraction of sulbactam, cefoperazone, and cefuroxime in whole blood.

In this study, we proposed a novel method utilizing polyethyleneimine (PEI)-modified halloysite nanotubes (HNTs)-based hybrid silica monolithic spin tip to analyze hydrophilic ß-lactam antibiotics and ß-lactamases inhibitors in whole blood samples for the first time. HNTs were incorporated directly into the hybrid silica monolith via a sol-gel method, which improved the hydrophilicity of the matrix. The as-prepared monolith was further modified with PEI by glutaraldehyde coupling reaction. It was found that the PEI-modified HNTs-based hybrid silica monolith enabled a large adsorption capacity of cefoperazone at 35.7 mg g-1. The monolithic spin tip-based purification method greatly reduced the matrix effect of whole blood samples and had a detection limit as low as 0.1 - 0.2 ng mL-1. In addition, the spiked recoveries of sulbactam, cefuroxime, and cefoperazone in blank whole blood were in the range of 89.3-105.4 % for intra-day and 90.6-103.5 % for inter-day, with low relative standard deviations of 1.3-7.2 % and 4.9-10.5 %, respectively. This study introduces a new strategy for preparing nanoparticles incorporated in a hybrid silica monolith with a high adsorption capacity. Moreover, it offers a valuable tool to monitor sulbactam, cefoperazone, and cefuroxime in whole blood from pregnant women with the final aim of guiding their administration.

In situ pulmonary mucus hydration assay using rotational and translational diffusion of gold nanorods with polarization-sensitive optical coherence tomography.

Significance: Assessing the nanostructure of polymer solutions and biofluids is broadly useful for understanding drug delivery and disease progression and for monitoring therapy. Aim: Our objective is to quantify bronchial mucus solids concentration (wt. %) during hypertonic saline (HTS) treatment in vitro via nanostructurally constrained diffusion of gold nanorods (GNRs) monitored by polarization-sensitive optical coherence tomography (PS-OCT). Approach: Using PS-OCT, we quantified GNR translational (DT) and rotational (DR) diffusion coefficients within polyethylene oxide solutions (0 to 3 wt. %) and human bronchial epithelial cell (hBEC) mucus (0 to 6.4 wt. %). Interpolation of DT and DR data is used to develop an assay to quantify mucus concentration. The assay is demonstrated on the mucus layer of an air-liquid interface hBEC culture during HTS treatment. Results: In polymer solutions and mucus, DT and DR monotonically decrease with increasing concentration. DR is more sensitive than DT to changes above 1.5 wt. % of mucus and exhibits less intrasample variability. Mucus on HTS-treated hBEC cultures exhibits dynamic mixing from cilia. A region of hard-packed mucus is revealed by DR measurements. Conclusions: The extended dynamic range afforded by simultaneous measurement of DT and DR of GNRs using PS-OCT enables resolving concentration of the bronchial mucus layer over a range from healthy to disease in depth and time during HTS treatment in vitro.

Transformation of a Viral Capsid from Nanocages to Nanotubes and Then to Hydrogels: Redirected Self-Assembly and Effects on Immunogenicity.

The ability to manipulate the self-assembly of proteins is essential to understanding the mechanisms of life and beneficial to fabricating advanced nanomaterials. Here, we report the transformation of the MS2 phage capsid from nanocages to nanotubes and then to nanotube hydrogels through simple point mutations guided by interfacial interaction redesign. We demonstrate that site 70, which lies in the flexible FG loop of the capsid protein (CP), is a "magic" site that can largely dictate the final morphology of assemblies. By varying the amino acid at site 70, with the aid of a cysteine-to-alanine mutation at site 46, we achieved the assembly of double-helical or single-helical nanotubes in addition to nanocages. Furthermore, an additional cysteine substitution on the surface of nanotubes mediated their cross-linking to form hydrogels with reducing agent responsiveness. The hierarchical self-assembly system allowed for the investigation of morphology-related immunogenicity of MS2 CPs, which revealed dramatic differences among nanocages, nanotubes, and nanotube hydrogels in terms of immune response types, antibody levels and T cell functions. This study provides insights into the assembly manipulation of protein nanomaterials and the customized design of nanovaccines and drug delivery systems.

Role of periodic irradiation and incident beam radius for plasmonic photothermal therapy of subsurface tumors.

Plasmonic photothermal therapy (PPTT) is a potential technique to treat tumors selectively. However, during PPTT, issue of high temperature region and damage to the surrounding healthy is still need to be resolved. Also, treatment of deeper tumors non-invasively is a challenge for PPTT. In this paper, the effect of periodic irradiation and incident beam radius (relative to tumor size) for various gold nanorods (GNRs) concentrations is investigated to avoid much higher temperatures region with limiting thermal damage to the surrounding healthy tissue during PPTT of subsurface breast tumors located at various depths. Lattice Boltzmann method is used to solve Pennes' bioheat model to compute the resulting photothermal temperatures for the subsurface tumor embedded with GNRs subjected to broadband near infrared radiation of intensity 1 W/cm2. Computation revealed that low GNRs concentration leads to uniform internal heat generation than higher GNRs concentrations. The results show that deeper tumors, due to attenuation of incident radiation, show low temperature rise than shallower tumors. For shallower tumors situated 3 mm deep, 70% irradiation period resulted in around 20 °C reduction (110 °C-90 °C) of maximum temperature than that with the continuous irradiation. Moreover, 70% beam radius (i.e., beam radius as 70% of the tumor radius) causes less thermal damage to the nearby healthy tissue than 100% beam radius (i.e., beam radius equal to the tumor radius). The thermal damage within the healthy tissue is minimized to the 1 mm in radial direction and 3 mm in axial direction for 70% beam radius with 70% irradiation period. Overall, periodic heating and changing beam radius of the incident irradiation lead to reduce high temperature and limit healthy tissue damage. Hence, discussed results are useful for selection of the irradiation parameters for PPTT of sub-surface tumors.

Evaluation of the surface characteristics and antibacterial properties of Titanium dioxide nanotube and methacryloyloxyethylphosphorylcholine (MPC) coated orthodontic brackets-a comparative invitro study.

OBJECTIVES: White spot lesions are the most common iatrogenic effect observed during orthodontic treatment. This study aimed to compare the surface characteristics and antibacterial action of uncoated and coated orthodontic brackets. MATERIALS AND METHODS: Sixty commercially available stainless steel brackets were coated with TiO2 nanotubes and methacryloyloxyethylphosphorylcholine. The sample was divided into Group 1: uncoated orthodontic brackets, Group 2: Stainless steel brackets with TiO2 nanotubes coating, Group 3: Stainless steel brackets with methacryloyloxyethylphosphorylcholine coating, and Group 4: Stainless steel brackets with TiO2 nanotubes combined with methacryloyloxyethylphosphorylcholine coating. Surface characterization was assessed using atomic force microscopy and scanning electron microscopy. Streptococcus mutans was selected to test the antibacterial ability of the orthodontic brackets, total bacterial adhesion and bacterial viability were assessed. The brackets were subjected to scanning electron microscopy to detect the presence of biofilm. RESULTS: The surface roughness was the greatest in Group 1 and least in Group 2 followed by Group 4 and Group 3 coated brackets. The optical density values were highest in Group 1 and lowest in Group 4. Comparison of colony counts revealed high counts in Group 1 and low counts in Group 4. A positive correlation between surface roughness and colony counts was obtained, however, was not statistically significant. CONCLUSIONS: The coated orthodontic brackets exhibited less surface roughness than the uncoated orthodontic brackets. Group 4 coated orthodontic brackets showed the best antibacterial properties. CLINICAL RELEVANCE: Coated orthodontic brackets prevent adhesion of streptococcus mutans and reduces plaque accumulation around the brackets thereby preventing formation of white spot lesions during orthodontic treatment.