Functionalized Gold Nanoparticles Research Articles

Application of coating based on 5 nm octadecylamine-functionalized gold-nanoparticles for protecting the spin-polarization of atoms confined in a vacuum cell

We report on the expressed atomic spin-polarization protection properties of thin layers of Octadecylamine capped gold-nanoparticles applied to the inner surface of an alkali metal vapor cell. The work aims to reveal the potential of using appropriately functionalized gold nanoparticles as a novel approach to forming efficient coatings on the inner surface of vacuum cells for atomic spectroscopy. The performed layer characterization uses parameters of electromagnetically induced transparency/absorption resonances observed in the Hanle configuration. We show at the Rb D2 absorption line that cells with such a coating provide conditions for achieving high-contrast and narrow, bright, and dark resonances, comparable to those reported by others for Octadecyltrichlorosilane coatings. Using visualization software for structural analysis, we represent the possible interaction scenarios between the alkali atoms and the surface building blocks. We demonstrate and discuss the main structural and functional differences introduced by covering the cell surface with passivated nanoparticles instead of directly using molecules to form monolayers. Having gold-nanoparticles in the coating allows preserving at the same time the earlier discovered advantage for high-speed control over the Rb vapor density by light-induced desorption of atoms. That enables significant problem-solving in atomic clocks and magnetometers and eases their considerable miniaturization.

Visual monitoring of polystyrene nanoplastics < 100 nm in drinking water based on functionalized gold nanoparticles

Nanoplastics (NPLs), of which polystyrene (PS) plastics are typical representatives, are of global concern as emerging contaminants, especially the leakage of NPLs into drinking water, which is directly related to human health. To onsite visually assess the extent of NPLs contamination in drinking water in a rapid and non-destructive manner, this work extends the application of the highly sensitive response to pH of mercaptoundecanoic acid (MUA)-functionalized gold nanoparticles (Au NPs). Further, a visual sensing method based on the binding of alkyl chains to PS NPLs with hydrophobic force to suppress pH-induced aggregation of functionalized nanoparticles was constructed. Particularly, the designed analytical strategy is a significant renewal of the first strategy for the visual detection of PS NPLs, featuring non-destructive, fast response (∼30 s), high selectivity, and detection limit (26 μg/L). Importantly, it can reliably distinguish the more hazardous PS NPLs of smaller particle size (<100 nm). Moreover, visualization-based detection observes the color change of the reaction solution from dark purple to wine red. The employment of a smartphone installed App to read the color three-channel value R further ensures the credibility of the analysis results. The proposed visual analysis strategy will provide a promising new avenue for efficient detection of surface hydrophobic NPLs and further evaluation of their particle size or shape.

A sensitive DNA biosensor based on the distance dependent quenching of Silica@Ru(bpy)32+‐chitosan‐GO electrochemiluminescence by Ferrocene@Gold nanoparticles

AbstractA sensitive electrochemiluminescence (ECL) biosensor for the specific DNA sequence of hepatitis C virus (HCV) was developed based on the efficient quenching effect of the ferrocene cluster functionalized gold nanoparticles (Fc@AuNPs) on the ECL of electrodeposited silica@Ru(bpy)32+‐chitosan‐graphene oxide nanocomposite (SiO2@Ru−CS−GO). Graphene oxide (GO) can accelerate electron transfer rate, thus improving the ECL of Ru(bpy)32+ on electrode surface. The molecular beacons (MB) was fixed to SiO2@Ru−CS−GO by glutaraldehyde (GA) using the Schiff reaction between amino groups of chitosan (CS) and MB. The ECL of SiO2@Ru−CS−GO was depressed greatly by the Fc@AuNPs labelled at the end of MB, then, a stronger ECL was observed when the distance between Fc@AuNPs and SiO2@Ru−CS−GO increased after the hybridization of target DNA with MB. Under optimum conditions, the restored ECL intensity increased linearly with the target DNA concentration in the range of 1.0×10−16∼1.0×10−10 mol ⋅ L−1, and the limit of detection (LOD) is 1.4×10−17 mol ⋅ L−1. The proposed method exhibits acceptable stability and reproducibility. In general, the constructed HCV biosensor can be used for the sensitive detection of HCV in human serum, suggesting potential application prospects in bioanalysis.

Experimental and Theoretical Study of Biosurfactants Functionalized Gold Nanoparticles for Mixture Detection and Chiral Recognition of Tryptophan by UV-VIS Spectroscopy

Background: Tryptophan (Trp) is an essential amino acid and plays important roles in biological processes. The detection of Trp is very important for its biological and chemical study. Moreover, Trp is a chiral compound; due to its importance in biological processes, researchers have been long committed to the chiral recognition and sensing of Trp enantiomers. Methods: Two biosurfactants, sodium cholate and sodium deoxycholate, were used for the preparation of functionalized gold nanoparticles (AuNPs) which were characterized by transmission electron microscope and potentiometer. UV-Vis spectra of functionalized gold nanoparticle solutions with different concentrations of Trp, tyrosine, phenylalanine, D-Trp, and L-Trp were analyzed. Then, the discrimination mechanism was further investigated, and the promotion mechanism of biosurfactants was studied by density functional theory (DFT). Results: Trp could induce the aggregation of unmodified AuNPs in 2 h, while phenylalanine and tyrosine could not. Adding biosurfactants promoted the aggregation process, and D- Trp rather than LTrp was found to be responsible for the aggregation. Therefore, there were interaction differences not only between Trp, phenylalanine, and tyrosine but also between Trp enantiomers. Conclusions: UV-vis spectroscopy could be applied for the direct detection of Trp in mixtures as well as the chiral recognition of Trp enantiomers. DFT calculations proved that the interactions of D-Trp with biosurfactants were the strongest, which contributes to the promotion of aggregation.

Nanomanipulation of Functionalized Gold Nanoparticles on GaN

Gold nanoparticles (AuNPs) is known for its high surface area to volume ratio which acts as an excellent receptor when placed in between electrodes in sensors application. Microelectrodes which are bar and needle shape pointed ends with two arrangements; comb and castle wall configurations were designed to be used for fabrication of electrodes to observe the relation between geometry of electrodes and dielectrophoretic of AuNPs on p-gallium nitride (GaN) substrates. The dielectrophoretic behaviour and electrical properties were analysed before and after the drop cast of AuNPs using current-voltage (I-V) curve method with manual probing. Resistance values of each sample were calculated under reverse bias condition. The effect of design on the nanomanipulation of AuNPs will be discussed.

Ultrasensitive Terahertz Biodetection Enabled by Quasi-BIC-Based Metasensors.

Advanced sensing devices, highly sensitive, and reliable in detecting ultralow concentrations of circulating biomarkers, are extremely desirable and hold great promise for early diagnostics and real-time progression monitoring of diseases. Nowadays, the most commonly used clinical methods for diagnosing biomarkers suffer from complicated procedures and being time consumption. Here, a chip-based portable ultra-sensitive THz metasensor is reported by exploring quasi-bound states in the continuum (quasi-BICs) and demonstrate its capability for sensing low-concentration analytes. The designed metasensor is made of the designed split-ring resonator metasurface which supports magnetic dipole quasi-BIC combining functionalized gold nanoparticles (AuNPs) conjugated with the specific antibody. Attributed to the strong near-field enhancement near the surface of the microstructure enabled by the quasi-BICs, light-analyte interactions are greatly enhanced, and thus the device's sensitivity is boosted significantly. The system sensitivity slope is up to 674 GHz/RIU, allowing for repeatable resolving detecting ultralow concentration of C-reactive protein (CRP) and Serum Amyloid A (SAA), respectively, down to 1 pM. The results touch a range that cannot be achieved by ordinary immunological assays alone, offering a novel non-destructive and rapid trace measured approach for next-generation biomedical quantitative detectionsystems.

Highly selective paper-based and colorimetric detection for arsenic(V) with methylene blue-functionalized gold nanoparticles

Paper-strip-type methylene blue (MB)-functionalized gold nanoparticles (AuNPs@MB) were developed and tested as colorimetric sensors for arsenic in this study. The valence state of arsenic speciation was pH-dependent, with arsenate (As(V)) exhibiting the HAsO42– form over the pH range of 7–11. When exposed to arsenic ions, AuNPs@MB exhibited significant agglomeration between nanoparticles via an ion-pairing mechanism between MB+ and As(V), resulting in a color shift from red to blue. The amount of MB loading on the AuNPs and the pH were adjusted to optimize the colorimetric sensing efficiency. AuNPs@MB-0.9 and AuNPs@MB-1.1 were employed as colorimetric sensors at low (0–30 ppb) and high (1–100 ppb) concentrations of As(V), respectively. To confirm the feasibility of using the AuNPs@MB sensor for As(V) detection, a selectivity test was conducted in the presence of 16 cations and 5 anions. This test demonstrated the practicality of the AuNPs@MB sensor for As(V) and showed that AuNPs@MB had a very high selectivity for As(V) compared to other cations and anions. Further, a solid-state colorimetric sensor based on a cellulose paper strip was developed for arsenic detection. The results of the paper-based colorimetric sensor with AuNPs@MB were the same as those of the solution-based colorimetric sensor.

Chiral gold nanoparticles/graphene oxide membranes with ultrahigh and stable permeance for sieving and enantioseparation

In accurately balancing membrane permeability and separation coefficient, effectively preventing membrane collapse in separation process is the core to improve the efficiency of membrane separation for two-dimensional materials. Here, we used L-cysteine (L-Cys) functionalized gold nanoparticles as scaffolds and spacers and fabricated a multi-effect separation membrane with GO nanosheets. The as-prepared membrane performed the following as a separation membrane: (1) As a robust spacer, the gold nanoparticles, prevented the collapse of the GO sheet and thus the membrane showed stability; (2) The existence of amphiphilic L-cysteine enabled the possibility of regulating the GO sheets layer spacing between 16.9 and 17.8 Å by pH, which achieves controllable ultrahigh permeance for size sieving. The maximum permeation rate of the membrane can reach 216.6 L m−2 h−1 bar−1, which is much greater than that of pure GO membrane; (3) Further, we demonstrate the following properties of the as-prepared membranes embedded with amphiphilic chiral gold nanoparticles for the enantiomer separation. The membrane has high enantioselectivity for Pen racemates, and its chiral separation factor and permeation rate can reach 1.83 and 21.7 L m−2 h−1 bar−1, respectively.

On-Site Detection of Neonicotinoid Pesticides Using Functionalized Gold Nanoparticles and Halogen Bonding.

Neonicotinoid (NN) pesticides have emerged globally as one of the most widely used agricultural tools for protecting crops from pest damage and boosting food production. Unfortunately, some NN compounds, such as extensively employed imidacloprid-based pesticides, have also been identified as likely endangering critical pollinating insects like honey bees. To this end, NN pesticides pose a potential threat to world food supplies. As more countries restrict or prohibit the use of NN pesticides, tools are needed to effectively and quickly identify the presence of NN compounds like imidacloprid on site (e.g., in storage areas on farms or pesticide distribution warehouses). This study represents a proof-of-concept where the colloidal properties of specifically modified gold nanoparticles (Au-NPs) able to engage in the rare intermolecular interaction of halogen bonding (XB) can result in the detection of certain NN compounds. Density functional theory and diffusion-ordered NMR spectroscopy (DOSY NMR) are used to explore the fundamental XB interactions between strong XB-donor structures and NN compounds, with the latter found to possess multiple XB-acceptor binding sites. A fundamental understanding of these XB interactions allows for the functionalization of alkanethiolate-stabilized Au-NPs, known as monolayer-protected gold clusters (MPCs), with XB-donor capability (f-MPCs). In the presence of certain NN compounds such as imidacloprid, the f-MPCs subsequently exhibit visual XB-induced aggregation that is also measured with absorption (UV-vis) spectroscopy and verified with transmission electron microscopy (TEM) imaging. The demonstrated f-MPC-aggregation detection scheme has a number of favorable attributes, including quickly reporting the presence of the NN target, requiring only micrograms of suspect material, and being highly selective for imidacloprid, the most prevalent and most important NN insecticide compound. Requiring no instrumentation, the presented methodology can be envisioned as a simple screening test in which dipping a cotton swab of an unknown powder from a surface in a f-MPC solution causes f-MPCs to aggregate and yield a preliminary indication of imidacloprid presence.

Visual colorimetric sensor for nitroguanidine detection based on hydrogen bonding−induced aggregation of uric acid−functionalized gold nanoparticles

A colorimetric assay is proposed for the quantification of nitroguanidine (NQ), based on triggering the aggregation of uric acid−modified gold nanoparticles (AuNPs@UA) by intermolecular hydrogen bonding interaction between uric acid (UA) and NQ. The red-to-purplish blue (lavender) color change of AuNPs@UA with increasing NQ concentrations could be perceived with the naked eye or detected by UV–vis spectrophotometry. The absorbance versus concentration correlation gave a linear calibration curve in the range of 0.6–3.2 mg L−1 NQ, with a correlation coefficient of 0.9995. The detection limit of the developed method was 0.063 mg L−1, lower than those of noble metal aggregation methods in the literature. The synthesized and modified AuNPs were characterized using UV–vis spectrophotometry, scanning transmission electron microscopy (STEM), dynamic light scattering (DLS), and Fourier transform infrared spectroscopy (FTIR). Some critical parameters such as modification conditions of AuNPs, UA concentration, solvent environment, pH, and reaction time were optimized for the proposed method. The non-interference of common explosives (i.e., nitroaromatic, nitramine, nitrate ester, insensitive and inorganic explosives), common soil and groundwater ions (Na+, K+, Ca2+, Mg2+, Cu2+, Fe2+, Fe3+, Cl−, NO3−, SO42−, CO32−, PO43−) and possible interfering compounds (used as camouflage agents for explosives; D-(+)-glucose, sweeteners, acetylsalicylic acid (aspirin), household powder detergents, and paracetamol) on the proposed method was demonstrated, proving that the procedure was fairly selective for NQ, due to special hydrogen bonding interactions between UA−functionalized AuNPs and NQ. Finally, the proposed spectrophotometric method was applied to NQ−contaminated soil, and the obtained results were statistically compared with those of the liquid chromatography-tandem mass spectrometric (LC-MS/MS) method in the literature.

SERS assisted sandwich immunoassay platforms for ultrasensitive and selective detection of human Thyroglobulin

We developed an immunoassay platform for the detection of human Thyroglobulin (Tg) to be integrated with fine-needle aspiration biopsy for early detection of lymph node metastases in thyroid cancer patients. The sensing platform detects Tg by a sandwich immunoassay involving a self-assembled surface-enhanced Raman scattering (SERS) substrate assisted by functionalized gold nanoparticles that provide additional Raman signal amplification and improved molecular specificity. Specifically, the SERS-active substrates were functionalized with Tg Capture antibodies and fabricated either on-chip or on optical fiber tips by nanosphere lithography. Gold nanoparticles were functionalized with Detection antibodies and conjugated with 4-mercaptobenzoic acid, which serves as a Raman reporter. The sandwich assay platform was validated in the planar configuration and a detection limit as low as 7 pg/mL was successfully achieved. Careful morphological examination of the SERS substrates before and after Tg measurements further assessed the effective capture of nanoparticles and correlated the average nanoparticle coverage with the Tg concentration obtained by SERS measurements. The sandwich assay was successfully demonstrated on washout fluids of fine needle aspiration biopsies from cancer patients and confirmed the high specificity of the proposed methodology when complex biological matrices are considered. Finally, SERS optrodes were fabricated and successfully used to detect Tg concentration by applying the same bio-recognition strategy and Raman interrogation through an optical fiber. This opens the possibility of transferring the Tg detection approach to the optical fiber tip to develop point-of-care platforms that can be directly integrated into fine needle aspiration biopsies.

Synthesis and Integration of Hybrid Metal Nanoparticles Covered with a Molecularly Imprinted Polymer Nanolayer by Photopolymerization.

Interfacing recognition materials with transducers has consistently presented a challenge in the development of sensitive and specific chemical sensors. In this context, a method based on near-field photopolymerization is proposed to functionalize gold nanoparticles, which are prepared by a very simple process. This method allows in situ preparation of a molecularly imprinted polymer for sensing by surface-enhanced Raman scattering (SERS). In a few seconds, a functional nanoscale layer is deposited by photopolymerization on the nanoparticles. In this study, the dye Rhodamine 6G was chosen as a model target molecule to demonstrate the principle of the method. The detection limit is 500 pM. Due to the nanometric thickness, the response is fast, and the substrates are robust, allowing regeneration and reuse with the same performance level. Finally, this method of manufacturing has been shown to be compatible with integration processes, allowing the future development of sensors integrated in microfluidic circuits and on optical fibers.

Correction: Exploiting the high conjugation capacity of creatinine on 3,3′-dithiodipropionic acid di(N-hydroxysuccinimide ester) functionalized gold nanoparticles towards sensitive determination of mercury (II) ion in water

Correction: Exploiting the high conjugation capacity of creatinine on 3,3′-dithiodipropionic acid di(N-hydroxysuccinimide ester) functionalized gold nanoparticles towards sensitive determination of mercury (II) ion in water

Recognition of malathion pesticides in agricultural samples by using α-CD functionalized gold nanoparticles as a colorimetric sensor

Herein, a rapid, precise alpha-cyclodextrin (α-CD) based gold nanoparticles (AuNPs) for selective detection of malathion pesticides has been reported. These are organophosphorus pesticides (OPPs), that can cause a neurological disease by inhibiting the activity of acetylcholinesterase (AChE). It is important to exploit a quick and sensitive approach for monitoring OPPs. Hence in the present work, a colorimetric assay for the detection of malathion has been developed as a model of OPPs from the environmental sample matrices. The physical and chemical properties of synthesized alpha-cyclodextrin stabilized gold nanoparticles (AuNPs/α-CD) were studied with various characterization techniques, including UV–visible spectroscopy, TEM, DLS and FTIR. The designed sensing system displayed linearity in the broad range of malathion concentrations, 10–600 ng mL−1 with a limit of detection and the limit of quantification values 4.03 ng mL−1 and 12.96 ng mL−1, respectively. The application of the designed chemical sensor was extended to the malathion pesticide determination in real samples such as vegetables, which resulted in almost 100% recovery rates in all the spiked samples. Thus, due to these advantages, the present study established a selective, facile and sensitive colorimetric platform for the direct detection of malathion within a very short time (5 min) with a low detection limit. The practicality of the constructed platform was further executed by the detection of the pesticide in vegetable samples.

Colorimetric detection of mercury (Hg2+) using UV-vis spectroscopy and digital image analysis based on gold nanoparticles functionalized with bromelain enzyme.

A very sensitive and selective colorimetric biosensor for the measurement of mercury ion (Hg2+) in environmental samples has been developed using functionalized gold nanoparticles with bromelain enzyme (brn-AuNPs). This work has shown that Hg2+ measurement based on spectrophotometer and digital image analysis is a very innovative and successful method for providing an effective preliminary system and has promise for the future of water quality biomonitoring. Response Surface Methodology (RSM), a Box-Behnken design-based technique, was used to identify the optimum levels of functionalization of bromelain to AuNPs. The created model's validity was confirmed, and statistical analysis revealed that the ideal functionalize conditions were 1mM of AuNPs, functionalize with 0.59mM bromelain concentration on 14℃ temperature and 72h incubation time. The lowest colorimetric detection concentration (LOD) of brn-AuNPs of Hg2+ was 0.0092ppm and 0.011ppm for spectrophotometer and digital image analysis. As shown, digital image analysis had advantages based on the LOD result comparable to UV-VIS spectrophotometer. The practical application of the brn-AuNPs sensing was proven with mercury determination in water samples. The present study developed a robust sensor, which successfully implemented in a compact portable sensor kit, turning this sensor into a very potent tool for the development water quality biomonitoring system of Hg2+ application.

Colorimetric Detection of Acenaphthene and Naphthalene Using Functionalized Gold Nanoparticles.

Polycyclic aromatic hydrocarbons are a class of chemicals that occur naturally. They generally demonstrate a high degree of critical toxicity towards humans. Acenaphthene and naphthalene contain compounds that are commonly found in the environment as compared to other PAHs. Consequently, a reliable method of detecting PAHs is crucial for the monitoring of water quality. A colorimetric method based on sodium nitrite-functionalized gold nanoparticles was developed in this study for acenaphthene and naphthalene detection. Different functionalized parameters are determined for the optimization of assay conditions. A linear relationship was found in the analyte concentration range of 0.1-10 ppm with the limit of detection for acenaphthene and naphthalene being 0.046 ppm and 0.0015 ppm, respectively, under the optimized assay conditions. The method's recovery rate for actual samples falls within the range of 98.4-103.0%. In selective and anti-interference tests, the presence of cations and anions has minimal impact on the detection of the analyte. The colorimetric detection method proposed in this study effectively determines the presence of the analyte in real water samples and has a high recovery rate.

Design of a nanobiosystem with remote photothermal gene silencing in Chlamydomonas reinhardtii to increase lipid accumulation and production

Research development in the precise control of gene expression in plant cells is an emerging necessity that would lead to the elucidation of gene function in these biological systems. Conventional gene-interfering techniques, such as micro-RNA and short interfering RNA, have limitations in their ability to downregulate gene expression in plants within short time periods. However, nanotechnology provides a promising new avenue with new tools to overcome these challenges. Here, we show that functionalized gold nanoparticles, decorated with sense and antisense oligonucleotides (FANSAO), can serve as a remote-control optical switch for gene interference in photosynthetic plant cells. We demonstrate the potential of employing LEDs as optimal light sources to photothermally dehybridize the oligonucleotides on the surface of metallic nanostructures, consequently inducing regulation of gene expression in plant cells. We show the efficiency of metallic nanoparticles in absorbing light from an LED source and converting it to thermal energy, resulting in a local temperature increase on the surface of the gold nanoparticles. The antisense oligonucleotides are then released due to the opto-thermal heating of the nanobiosystem composed of the metallic nanoparticles and the sense-antisense oligonucleotides. By applying this approach, we silenced the Carnitine Acyl Carnitine Translocase genes at 90.7%, resulting in the accumulation of lipid bodies in microalgae cells. These results exhibit the feasibility of using functionalized gold nanoparticles with sense and antisense oligonucleotides to enhance nucleic acid delivery efficiency and, most importantly, allow for temporal control of gene silencing in plant cells. These nanobiosystems have broad applications in the development and biosynthesis of biofuels, pharmaceuticals, and specialized chemicals.

Selective Colorimetric Sensing of Fluoride Ion in Water by 4-Quinonimine Functionalized Gold Nanoparticles

Selective Colorimetric Sensing of Fluoride Ion in Water by 4-Quinonimine Functionalized Gold Nanoparticles

A rapid direct-differential agglutination assay for Brucella detection using antibodies conjugated with functionalized gold nanoparticles

Brucellosis is the most widespread and serious zoonotic disease worldwide which affects livestock, sylvatic wildlife, marine dwellers, and humans. It is acquired through Alphaproteobacteria which belong to the genus Brucella and is categorized as a potential bio-threat agent. In this study, we developed a rapid and direct differential whole cell (WC) agglutination-based assay for its on-field detection. The recombinant outer membrane (rOmp28) protein-derived specific mice IgG polyclonal antibodies (pAbs) of Brucella were purified using affinity chromatography and conjugated with functionalized gold nanoparticles (AuNPs) for rapid agglutination. A positive blot of 32 kDa protein revealed specific immuno-reactivity of rOmp28-pAbs using immunoblot analysis. For the synthesis of AuNPs, the conventional “Turkevich method” was optimized at a concentration &amp;lt; 1 mM of gold precursor for obtaining 50-nm-sized particles. Also, their physico-chemical characteristics were analyzed using UV-visible spectrophotometry, Fourier transform infra-red spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential (ζ, ZP), and fluorescence spectroscopy. Furthermore, these AuNPs were functionalized with N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) to prepare modified carboxylated AuNPs. For bioconjugation with Brucella rOmp28 IgG pAbs, antibody-conjugated functionalized AuNP constructs were prepared and characterized using FT-IR analysis with strong N–H deformations. Subsequently, these bioconjugated AuNPs were used to develop a direct-differential slide agglutination assay with a detection limit of 104 CFU mL−1. The sensitivity of this assay was compared with standard double-antibody sandwich ELISA (S-ELISA) using rOmp28 IgG pAbs with an LOD of 103 CFU mL−1 and a detection range of 102–108 CFU mL−1. No intraspecies cross-reactivity was observed based on evaluation of its specificity with a battery of closely related bacterial species. In conclusion, the increased sensitivity and specificity of the developed agglutination assay obtained using bioconjugated functionalized AuNPs is ≥ 98% for the detection of Brucella. Therefore, it can be used as an alternate rapid method of direct WC detection of bacteria as it is simple, robust, and cost-effective, with minimal time of reaction in the case of early disease diagnosis.

Insight into the Lysozyme-Induced Aggregation of Aromatic Amino Acid-Functionalized Gold Nanoparticles: Impact of the Protein Conjugation and Lipid Corona on the Aggregation Phenomena.

The aggregation and subsequent precipitation of gold nanoparticles (Au NPs) in the presence of protein molecules restrict the usefulness of NPs in biomedical applications. Till now, the influence of different properties of Au NPs (size, surface charge, surface coatings) and proteins (surface charge, chemical modification, folded and unfolded states) and pH and ionic strength of the solution on the aggregation of both Au NPs and proteins has been thoroughly discussed in the literature. However, the underlying different mechanistic pathways of the protein concentration-dependent aggregation of both Au NPs and proteins are poorly understood. The impact of the lipid corona on the protein-induced Au NP aggregation has remained an unresolved issue. In this context, we investigate the interaction of the negatively charged aromatic amino acid (phenylalanine and tyrosine)-functionalized gold nanoparticles (Au-AA NPs) with the positively charged globular protein lysozyme at different protein concentrations and compare the results with those of conventional citrate-functionalized Au NPs (Au-Cit NPs). Next, we conjugate lipids and proteins to Au NPs to impede the aggregation of Au NPs induced by the lysozyme. Our results reveal that the aggregation mechanism of the Au-AA NPs is distinctly different at low and high protein concentrations with the uniqueness of the Au-AA NPs over the Au-Cit NPs. Furthermore, we find that human serum albumin (HSA) protein-conjugated Au-AA and Au-Cit NPs are more effective in preventing the lysozyme-induced Au NP aggregation than bovine serum albumin (BSA)-conjugated Au NPs. For the first time, we also report the significant role of "hard" and "soft" lipid coronas in the aggregation of amino acid (phenylalanine)-functionalized gold nanoparticles in the presence of lysozyme protein.