Deposition Of Silver Nanoparticles Research Articles

Silver spray deposition for AgLDI imaging MS of cholesterol and other olefins on thin tissue sections.

Olefins such as cholesterol and unsaturated fatty acids play important biological roles. Silver-assisted laser desorption ionization (AgLDI) takes advantage of the strong affinity of silver to conjugate with double bonds to selectively ionize these molecules for imaging mass spectrometry (IMS) experiments. For IMS studies, two main approaches for silver deposition have been described in the literature: fine coating by silver sputtering and spray deposition of silver nanoparticles. While these approaches allow for extremely high resolution IMS experiments to be conducted, they are not readily available to all laboratories. Herein, we present a silver nitrate spray deposition approach as an alternative to silver sputtering and nanoparticle deposition for routine IMS analysis. The silver nitrate spray has the same level of specificity and sensitivity for olefins, particularly cholesterol, and has shown to be capable of IMS experiments down to 10-μm spatial resolution. Minimal sample preparation and the affordability of silver nitrate make this a convenient and accessible technique worth considering.

A multiple signal amplification sandwich-type SERS biosensor for femtomolar detection of miRNA

MicroRNAs are widely used as tumor markers for cancer diagnosis and prognosis. Herein, a multiple signal amplification sandwich-type SERS biosensor for femtomolar detection of miRNA is reported. The signal unit consisted of giant Au vesicles, DNA sequences and deposited silver nanoparticles. The giant Au vesicles provided large-volume hot spots because of sharp tips and abundant hotspot gaps, thus enhancing the electromagnetic intensity for the SERS performance. Further silver stain would easily lead to second-stage amplification of Raman signal. In addition, more SERS signal molecules R6G adsorbed on the signal unit with the aid of HCR and the controlled nanogaps between adjacent AgNPs, brought about the third-stage amplification. The capture unit, prepared by immobilizing the capture probe (CP) on the Fe3O4@AuNPs, could easily capture target miRNA and greatly simplify the separation step to improve reproducibility. The higher concentration of target miRNA definitely formed more sandwich-type structures with combination of capture unit and signal unit, resulting in multiple amplification of SERS signals. The proposed multiple signal amplification sandwich-type SERS biosensor could detect miRNA-141 at the femtomolar level with a low detection limit of 0.03 fM. Meanwhile, it exhibited high selectivity and accuracy, even for practical analysis in human serum. Therefore, the designed multiple signal amplification sandwich-type SERS biosensor would be a very promising alternative tool for the detection of miRNA and analogs in the field of biomedical diagnosis.

High-speed production of antibacterial fabrics using liquid flame spray

Healthcare associated infections (HAIs) are known as one of the major problems of the modern healthcare system, which result in additional cost and mortality. It has also been shown that pathogenic bacteria are mostly transferred via surfaces in healthcare settings. Therefore, antibacterial surfaces, which include fabrics and textiles, can be used in a healthcare environment to reduce the transfer of pathogenic bacteria, hence reducing HAIs. Silver nanoparticles have been shown to have broad spectrum antibacterial properties, and therefore they have been incorporated into fabrics to provide antibacterial functionality. Liquid flame spray (LFS) nanoparticle synthesis allows nanoparticles to be produced and deposited on surfaces at speeds up to and beyond 300 m/min. Herein, LFS is used to deposit silver nanoparticles onto two fabrics that are commonly used in the hospital environment with the aim of producing antibacterial fabrics. A thin plasma coating on top of the fabrics after silver deposition is used to improve nanoparticle adhesion. Fabrics coated with silver nanoparticles demonstrated antibacterial properties against Escherichia coli. Nanoparticle imaging and surface chemical characterization are performed using scanning electron microscopy and X-ray photoelectron spectroscopy. The highlights of this research are as follows: • high-speed synthesis and deposition of silver nanoparticles on fabrics; • plasma coating onto fabrics with silver nanoparticles; • antibacterial fabrics for potential use in healthcare environments.

“Rinse, Repeat”: An Efficient and Reusable SERS and Catalytic Platform Fabricated by Controlled Deposition of Silver Nanoparticles on Cellulose Paper

Grafting metal nanoparticles (NPs) on flexible platforms is being increasingly attempted to advance their usage in the field of catalysis, sensing, energy storage, etc. However, anchoring NPs on su...

Silver nanoparticles deposition on silica, magnetite, and alumina surfaces for effective removal of Allura red from aqueous solutions

Silica, magnetite, and alumina surfaces were modified firstly by the coupling agent 3-Aminopropyltriethoxysilane. Silver nanoparticles were thus immobilized in the given functionalized surfaces via chemical reduction in aqueous solution using different reducing agents. The immobilized silver nanoparticles on the support surfaces were confirmed by the scanning electron microscopy, energy dispersive X-ray analysis, transmission electron microscopy, Fourier transform infrared spectroscopy, and thermogravemetric analysis. The efficiency of the synthesized nanocomposites for the removal of Allura red from aqueous solution has been assessed through some of experimental conditions. These include the type of support, type of reducing agent, initial dye concentration, adsorbent dose, temperature, and pH. The experimental data were analyzed by the Langmuir, Freundlich, and Temkin isotherm models. The results followed the order: Langmuir > Temkin > Freundlich. Values of thermodynamic parameters (∆Go, ∆Ho, and ∆So) of dye adsorption onto the surface of silica/silver nanoparticles, magnetite/silver nanoparticles, and alumina/silver nanoparticles were determined. They refer to the feasibility, spontaneity, and endothermic nature of dye adsorption on these surfaces. The adsorption process fitted well with pseudo-second-order kinetics and intraparticle diffusion model. This method can thus be considered applicable for the decontamination of wastewater from dyes.

A silver-nanoparticle/cellulose-nanofiber composite as a highly effective substrate for surface-enhanced Raman spectroscopy.

A highly active surface-enhanced Raman scattering (SERS) substrate was developed by facile deposition of silver nanoparticles onto cellulose fibers of ordinary laboratory filter paper. This was achieved by means of the silver mirror reaction in a manner to control both the size of the silver nanoparticles and the silver density of the substrate. This paper-based substrate is composed of a particle-on-fiber structure with the unique three-dimensional network morphology of the cellulose matrix. For such a SERS substrate with optimized size of the silver nanoparticles (ca. 70 nm) and loading density of silver (17.28 wt %), a remarkable detection limit down to the sub-attomolar (1 × 10−16 M) level and an enhancement factor of 3 × 106 were achieved by using Rhodamine 6G as the analyte. Moreover, this substrate was applied to monitor the molecular recognition through multiple hydrogen bonds in between nucleosides of adenosine and thymidine. This low-cost, highly sensitive, and biocompatible paper-based SERS substrate holds considerable potentials for the detection and analyses of chemical and biomolecular species.

The influence of initial gold nanoparticles layer on migration of silver nanoparticles in silver/glass matrix

A thin layer of gold nanoparticles (AuNPs) was deposited on glass substrates followed by subsequent deposition of silver nanoparticles (AgNPs) on it. Both AuNPs and AgNPs layers were fabricated by DC magnetron sputtering with inert gas condensation technique. The effect of initial thin layer of AuNPs have on the transformation of AgNPs surface structure by post annealing at 500 °C and 600 °C in air was investigated. The influence of post annealing temperature on the surface morphology was studied by atomic force microscopy and post annealing at 500 °C reduce the size of AgNPs along with the formation of some AgNPs inside the glass matrix. At 600 °C, aggregation of AuNPs on the surface was observed and increased in the number of AgNPs that diffused into the glass matrix. X-ray photoelectron spectroscopy was employed to study the surface composition and chemical states. The temperature dependence of Ag diffusion into the glass matrix was characterised and observed by UV–visible absorption spectroscopy and cross sectional transmission electron microscopy. Furthermore, ultraviolet photoelectron spectroscopy revealed a new shoulder related to Au 6 s hybridized with Au 5d and Ag 4d bands in the 1–4 eV regions, which affirmed the metallic character of AgNPs/AuNPs/glass system at higher annealing temperature. By introducing AuNPs on glass prior to AgNPs deposition, novel properties such as limited Ag ion diffusion and evaporation were found and problems previously encountered in AgNPs/glass system were avoided. The proposed AgNPs/AuNPs/glass system can be useful in plasmonic applications such as chroma filters and photonic devices.

Rapid Isolation and Identification of Pneumonia-Associated Pathogens from Sputum Samples Combining an Innovative Sample Preparation Strategy and Array-Based Detection.

With this study, an innovative and convenient enrichment and detection strategy for eight clinically relevant pneumonia pathogens, namely, Acinetobacter baumannii, Escherichia coli, Haemophilus influenzae, Klebsiella pneumoniae, Moraxella catarrhalis, Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus pneumoniae is introduced. Bacteria were isolated from sputum samples with amine-modified particles exploiting pH-dependent electrostatic interactions between bacteria and the functionalized particle surface. Following this, an asymmetric polymerase chain reaction as well as subsequent stringent array-based hybridization with specific complementary capture probes were performed. Finally, results were visualized by an enzyme-induced silver nanoparticle deposition, providing stable endpoint signals and consequently an easy detection possibility. The assay was optimized using spiked samples of artificial sputum with different strains of the abovementioned bacterial species. Furthermore, actual patient sputum samples with S. pneumoniae were successfully analyzed. The presented approach offers great potential for the urgent need of a fast, specific, and reliable isolation and identification platform for important pneumonia pathogens, covering the complete process chain from sample preparation up to array-based detection within only 4 h.

The fabrication of a high-sensitivity surface-enhanced Raman spectra substrate using texturization and electroplating technology

A method for preparing surface-enhanced Raman scattering substrate with high sensitivity is presented in this study. The new type of substrate was fabricated by depositing silver nanoparticles, using electroplating, onto the surface of boron-doped single silicon with a texture of inverted pyramid arrays prepared by the technology of texturization. In order to evaluate the enhancement ability of the substrate, a test of Raman scattering with Rhodamine 6G (R6G) as probe molecules was performed and the results showed a high sensitivity, good uniformity and stability. Relay on the enhancement by the substrate, the Raman scattering signal of R6G with a high signal-to-noise ratio could be detected out at a rather low concentration level of 10−18 M. The performance of the substrate is also simulated and illustrated using the software COMSOL Multiphysics. The electric field is greatly enhanced on the surface of silicon wafer with inverted pyramid morphology, especially in pits. According to the electromagnetic enhancement theory, the calculated Raman enhancement factor is as high as 1011, which strongly supports the experimental data. This work may offer a novel and practical method for Raman spectroscopy application in trace analysis.

Accurate controlled deposition of silver nanoparticles on porous silicon by drifted ions in electrolytic solution

In this study, a low-cost, simple, single-step low-voltage operation and a well-controlled method for deposition of uniformed and unique size distributions of silver nanoparticles (AgNPs) on the porous silicon (PS) layer were achieved via controlling the drift velocity of electrons in an aqueous solution of AgNO3. The laser diode of 530 nm and 60 mW/cm2 laser wavelength and illumination power density was employed to prepare PS layer by a laser-assisted etching process. The PS layer was incorporated on the platinum disk cathode electrode, and a stainless steel plate as an anode was employed. Low applied operating voltage of about 3V DC at different drift currents of 10, 20, 30 and 40 mA for 2 min was applied to sustain the drift motion of Ag2+. Structural properties of AgNPs layer were examined via the field emission scanning electron microscope (FE-SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD) pattern. These measurements exposed that AgNPs were adjusted by controlling the drift current, and a uniform AgNPs with specific unique sizes were obtained. Grain size, specific surface area and nucleation sites of metallic AgNPs were intensely influenced by the drift current.

Plasma-enhanced magnetron sputtering of silver nanoparticles on reverse osmosis membranes for improved antifouling properties

The reverse osmosis process is an efficient water purification technology with comparatively low energy consumption. However, unwanted biofilm formation remains a major challenge for membrane plant operators, and effective fouling control strategies are highly sought for. A material-based antifouling approach is the deposition of silver nanoparticles onto the polyamide layer of thin film composite membranes by plasma-enhanced magnetron sputtering, as described in this study. The particle size and distributions were analyzed from Scanning Electron Microscopy (SEM) images and discussed with the elemental composition of the membrane surfaces derived by X-ray Photoelectron Spectroscopy (XPS). The desalination efficiency of the silver coated membranes was determined by use of a coupon tester, and the antimicrobial effect was verified by inducing a reproducible microbial stress on the membranes with a chemostat. In the presence of silver nanoparticles, which had an average diameter of 30 nm, the biofilm formation of pseudomonas sp. was significantly reduced by 64.6% on average after 14 days of continuous cultivation. A sputtering time of 5 s proved to be successful both in significantly improving the antifouling properties as well as fully maintaining the filtration performance of the membranes.

Enhancement of antibacterial properties of various polymers functionalized with silver nanoparticles

A new green deposition of silver nanoparticles (AgNPs) on polymers was proposed in this work. In-situ synthesis of AgNPs on polymers was achieved via a green procedure using natural reducing agents, which are Ageratum conyzoidez and Mikania micrantha. Several characterizations of the treated polymers such as color transformation, surface morphology, elemental contents, and water absorption were comprehensively evaluated. For the application, the treated polymers were then tested against waterborne bacteria, which are Escherichia coli and Bacillus cereus. Rapid deposition of AgNPs via the presently biological method can be successfully achieved as observed via surface morphology analysis and energy dispersive X-ray investigation. Water absorption capabilities of the polymers can be decreased after attaching with AgNPs, which can also probably contribute to the enhancement of their antibacterial activities. This study observed that the treated polymers showed excellent antibacterial activities against Escherichia coli and Bacillus cereus. The findings of this study are useful in designing water purifiers to disinfect contaminated water.

Increased Degradation Capacity of Methylene Blue Dye Using Mg-doped ZnO Nanoparticles Decorated by Ag0 Nanoparticles

Photocatalytic activity has been widely used for the treatment of organic effluents, mainly those generated by textile industries. Zinc oxide is widely investigated for this application due to its low cost, non-toxicity and high efficiency. In this work, the photocatalytic properties of ZnO:xMg (x = 1 mol.%, 2 mol.%, 4 mol.% and 8 mol.%) decorated with Ag0 were investigated against methylene blue dye (MB). Initially, the nanostructures of ZnO:xMg were produced by the microwave-assisted hydrothermal method, and the nanoparticles of Ag0 were deposited by ultraviolet (UV) photoreduction. The structural characteristics of the powders were determined by x-ray diffraction, the morphologies were investigated by field emission scanning electron microscopy (FE-SEM) and the optical absorbance of the photocatalysts was characterized by the diffuse reflectance spectra [UV–visible light (UV–Vis)]. The photocatalytic properties were estimated by degradation of MB, and the capacity for reuse of the powders was estimated by application in three consecutive cycles. Undoped ZnO powders reduced 84% of MB concentration, while the ZnO:8%Mg sample reduced 97% of it, indicating that doping with Mg2+ is efficient in increasing the degradation capacity of ZnO against MB degradation. The deposition of metallic silver nanoparticles on the ZnO surface considerably increases the photocatalytic efficiency, in which after 18 min, the 8%Mg sample completely degraded the MB. The reuse tests showed that the powders maintain their photocatalytic activity after three cycles and can be used for such application without generating secondary residues.

Preparation of silver nanoparticle functionalized polyamide fibers with antimicrobial activity and electrical conductivity

ABSTRACTIn this work, silver nanoparticle functionalized polyamide 6 (PA6) fibers were prepared using the electroless plating method. The surface of PA6 fibers was modified by exploiting dopamine/CuSO4/H2O2 system prior to electroless plating to enhance the bonding force between the fiber and the silver nanoparticles. It was found that both the formation rate and the chemical stability of polydopamine (PDA) coatings on the PA6 fiber surface were improved by the introduction of CuSO4/H2O2. The results confirmed the successful deposition of silver nanoparticles on PA6 fiber surface and the average particle diameter of 223 nm. Compared with uncoated fibers, the silver plated PA6 fibers exhibited excellent antimicrobial activity to both Escherichia coli and Staphylococcus aureus (with an antimicrobial efficiency of 99.9% and 100%, respectively). The electrical resistance of the silver coated PA6 fibers reached 0.98 Ω over a length of 1 cm, indicating a good electrical conductivity. In particular, coating durability of the formed silver layer was investigated by subjecting the fibers to various mechanical deformations, and the results showed that the formed silver layer was maintained well after 50 times of cyclic stretching at a constant displacement of 10 mm. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47584.

Ultrasensitive quantification of paraquat using a newly developed sensor based on silver nanoparticle-decorated carbon nanotubes

Present work introduces a novel electrochemical sensor that developed based on glassy carbon electrode modified by Nafion coating on the multiwall carbon nanotubes decorated with the electrochemically deposited silver nanoparticles, N/AgNP/MWCNT/GCE. Application of the metal nanoparticles and Nafion in the modification of the MWCNTs casted on the GCE surface significantly enhanced the sensitivity and stability of the GCE response toward paraquat (PQ) and omitted or reduced the potential effects of the interferences on the PQ quantification. The proposed procedure showed a wide linear quantification range of 0.1–10 µM with a high sensitivity of 5.47 µA/µM and a very low detection limit of 68 nM. This sensor was employed for PQ determination in real samples with good recovery outcomes. N/AgNP/MWCNT/GCE showed good anti-interfering effect toward the component of the orange juice revealing its applicability for real sample analysis.

Enhanced fluorescence in nano-multiferroic fluoride substrates attached with silver nanoparticles

Nano-multiferroic BaMF4 (M = Mn, Mg) are synthesized in pure-phase by hydrothermal method as fluoride substrates. The Mn2+ stokes emission and the Tm3+ anti-stokes emission are shown in BaMnF4 and BaMgF4: Yb3+, Tm3+ nanocrystals under 465 and 975 nm excitation respectively. By depositing silver nanoparticles with the AgNO3/BaMF4 ratio of 0.01:1, the 347&365, 455, 480, 640 and 700 nm emissions of Tm3+ are enhanced 27, 21, 6, 3 and 2 times respectively, also the 700 nm emission of Mn2+ is enhanced 2 time. The above mentioned enhancement factor versus emission wavelength is accordance with the nano-silver absorption wavelength, indicating the surface plasmon coupled emission (SPCE) inducted by excited luminescent ions.

Deposition of catechol-functionalized chitosan and silver nanoparticles on biomedical titanium surfaces for antibacterial application

The titanium (Ti) and its alloys have been widely used for dental and orthopedic implants. However, the Ti-based implants may suffer from bacterial infection, which would result in insufficient healing, implant failure and repeated surgical intervention. It is of great interest to inhibit the bacterial adhesion and colonization on the Ti-based implants by introducing proper surface coatings. In this work, a simple method was employed to synthesize the water-soluble catechol-containing chitosan (CACS). The CACS coatings can be deposited onto various substrate surfaces and exhibit substrate-independent behavior. The CACS-coated Ti surfaces were further deposited with silver nanoparticles (Ag NPs) via in-situ reduction of Ag+ ions using catechol moieties as the reducing agents. The resulting AgNPs/CACS-coated Ti surfaces exhibit antibacterial properties and can prevent the surface adhesion of bacterial cells, as evidenced by the inhibition zone test, live/dead bacterial staining assay and spread plate method. In addition, they show negligible cytotoxicity to L929 mouse fibroblast cells.

Lobar evenness of deposition/retention in rat lungs of inhaled silver nanoparticles: an approach for reducing animal use while maximizing endpoints

BackgroundInformation on particle deposition, retention and clearance are important for the evaluation of the risk of inhaled nanomaterials to human health. Recent revised OECD inhalation toxicity test guidelines require to evaluate the lung burden of nanomaterials after rodent subacute and subchronic inhalation exposure (OECD 412, OECD 413). These revised test guidelines require additional post-exposure observation (PEO) periods that include lung burden measurements that can inform on lung clearance behavior and translocation. The latter being particularly relevant when the testing chemical is a solid poorly soluble nanomaterial. Therefore, in the spirit of 3 R’s, we investigated whether measurement of retained lung burden of inhaled nanoparticles (NPs) in individual lung lobes is sufficient to determine retained lung burden in the total lung. If it is possible to use only one lobe, it will reduce animal use and maximize the number of endpoints evaluated.ResultsTo achieve these goals, rats were exposed nose-only for 1 or 5 days (6 h/day) to an aerosol of 20 nm well-dispersed silver nanoparticles (AgNPs), which is the desired particle diameter resulting in maximum deposition in the pulmonary region when inhaled as singlets. After exposure, the five lung lobes were separated and silver concentration was measured using inductively coupled plasma-mass spectrophotometer (ICP-MS). The results showed that the retention of deposited silver nanoparticle in the different lung lobes did not show any statistically significant difference among lung lobes in terms of silver mass per gram lung lobe. This novel finding of evenness of retention/deposition of inhaled 20 nm NPs in rats for all five lobes in terms of mass per unit tissue weight contrasts with earlier studies reporting greater apical lobe deposition of inhaled micro-particles in rodents. The difference is most likely due to preferred and efficient deposition of inhaled NPs by diffusion vs. additional deposition by sedimentation and impaction for micron-sized particles.ConclusionAgNPs following acute inhalation by rats are evenly retained in each lung lobe in terms of mass per unit lung tissue weight. Accordingly, we suggest sampling any of the rat lung lobes for lung burden analysis can be used to determine deposited or retained total lung burden after short-term inhalation of NPs and using the other lobes for collecting and analyzing bronchoalveolar lavage fluid (BALF) and for histopathological analysis. Therefore, by combining lung burden measurement, histopathological tissue preparation, and BALF assay in the same rat will reduce the number of animals used and maximize the number of endpoints measured.

In Situ Deposition of Silver Nanoparticles on Polydopamine Nanospheres for an Ultrasensitive Electrochemical Aptasensor of Ochratoxin A

This work proposed a novel and facile strategy for in-situ deposition of silver nanoparticles (AgNPs) on polydopamine nanospheres (PDANSs), and used the as-synthesized nanocomposite (AgNPs/PDANSs) as electrochemical tracer for an ultrasensitive aptasensor of ochratoxin A (OTA). The morphology and composition of PDANSs and AgNPs/PDANSs were characterized by electron microscopies and energy dispersive X-ray spectroscopy, and the results showed that AgNPs uniformly on PDANSs surface. AgNPs/PDANSs were combined with streptavidin (SA) to obtain signal probe for constructing of OTA aptasensor. Sequentially, the thiolated capture DNA (cDNA) was firstly immobilized on the gold electrode (GE) to capture the OTA aptamer, and then SA/AgNPs/PDANSs nanoprobes could bind with the end biotin of the aptamer through biotin-streptavidin biorecognition. The monitoring of the proposed OTA aptasensor was realized by the electrochemical stripping signal of AgNPs on PDANSs, and PDANSs was used for signal amplification. In the presence of OTA, the aptamer was preferentially bonded with OTA because of their high affinity, and resulted in the decrease of signal tags on the aptasensor surface, which reduced the electrochemical response signal of AgNPs. Under optimal experimental conditions, the proposed aptasensor offered a wide linear range from 1.0 × 10−6 μM to 1.0 × 10−2 μM and a low detection limit of 0.57 pM (S/N = 3). Meanwhile, This AgNPs/PDANSs-based OTA aptasensor had excellent specificity, stability and reproducibility, and was successfully employed for OTA detection in red wine samples, which showed promising application in electrochemical analysis of other toxic molecules.

Fabrication of Silver Nanoparticles Using a Gas Phase Nanocluster Device and Preliminary Biological Uses.

Nanoparticles can be used in a large variety of applications, including magnetic sensing, biological, superconductivity, tissue engineering, and other fields. In this study, we explore the fabrication of gas phase silver nanoparticles using a sputtering evaporation source. This setup composed of a dual magnetron cluster source holds several advantages over other techniques. The system has independent control over the cluster concentration and a wide range of cluster size and materials that can be used for the clusters and for the matrix where it can be embedded. Characterization of these silver nanoparticles was done using transmission electron microscopy (TEM). We obtain a lateral width of 10.6 nm with a dispersion of 0.24 nm. With atomic force microscopy (AFM) a Gaussian fit of this distribution yields and average height of 6.3 nm with a standard deviation of 1.4 nm. We confirm that the deposited silver nanoparticles have a homogenous area distribution, that they have a defined shape and size distribution, and that they are single standing nanoparticles. Given that the scientific literature is not precise regarding the toxic concentration of the nanoparticles, devices such as ours can help clarify these questions. In order to explore further biological applications, we have done preliminary experiments of cell spreading (myoblast adhesion), obtaining interesting morphological changes correlated with the silver concentration on the surface. With a deposited silver concentration ranging from 100–620 ng/cm2, the cells showed morphological changes in a short time of 2 h. We conclude that this high precision nanoparticle fabrication technique is adequate for further biological research.