Intracellular uptake,transport, and processing of gold nanostructures

Abstract

The emerging field of nanomedicine requires better understanding of the interface between nanotechnology and medicine. Better knowledge of the nano-bio interface will lead to better tools for diagnostic imaging and therapy. In this review, recent progress in understanding of how size, shape, and surface properties of nanoparticles (NPs) affect intracellular fate of NPs is discussed. Gold nanostructures are used as a model system in this regard since their physical and chemical properties can be easily manipulated. The NP-uptake is dependent on the physiochemical properties, and once in the cell, most of the NPs are trafficked via an endo-lysosomal path followed by a receptor-mediated endocytosis process at the cell membrane. Within the size range of 2–100 nm, Gold nanoparticles (GNPs) of diameter 50 nm demonstrate the highest uptake. Cellular uptake studies of gold nanorods (GNRs) show that there is a decrease in uptake as the aspect ratio of GNRs increases. Theoretical models support the size- and shape-dependent NP-uptake. The intracellular transport of targeted NPs is faster than untargeted NPs. The surface ligand and charge of NPs play a bigger role in their uptake, transport, and organelle distribution. Exocytosis of NPs is dependent on size and shape as well; however, the trend is different compared to endocytosis. GNPs are now being incorporated into polymer and lipid based NPs to build multifunctional devices. A multifunctional platform based on gold nanostructures, with multimodal imaging, targeting, and therapeutics; hold the possibility of promising directions in medical research.     

Intracellular uptake, transport, and processing of gold nanostructures

The emerging field of nanomedicine requires better understanding of the interface between nanotechnology and medicine. Better knowledge of the nano-bio interface will lead to better tools for diagnostic imaging and therapy. In this review, recent progress in understanding of how size, shape, and surface properties of nanoparticles (NPs) affect intracellular fate of NPs is discussed. Gold nanostructures are used as a model system in this regard since their physical and chemical properties can be easily manipulated. The NP-uptake is dependent on the physiochemical properties, and once in the cell, most of the NPs are trafficked via an endo-lysosomal path followed by a receptor-mediated endocytosis process at the cell membrane. Within the size range of 2-100 nm, Gold nanoparticles (GNPs) of diameter 50 nm demonstrate the highest uptake. Cellular uptake studies of gold nanorods (GNRs) show that there is a decrease in uptake as the aspect ratio of GNRs increases. Theoretical models support the size- and shape-dependent NP-uptake. The intracellular transport of targeted NPs is faster than untargeted NPs. The surface ligand and charge of NPs play a bigger role in their uptake, transport, and organelle distribution. Exocytosis of NPs is dependent on size and shape as well; however, the trend is different compared to endocytosis. GNPs are now being incorporated into polymer and lipid based NPs to build multifunctional devices. A multifunctional platform based on gold nanostructures, with multimodal imaging, targeting, and therapeutics; hold the possibility of promising directions in medical research.     

Gold Nanoring Arrays for Near Infrared Plasmonic Biosensing

Gold nanoring array surfaces that exhibit strong localized surface plasmon resonances (LSPR) at near infrared (NIR) wavelengths from 1.1 to 1.6 μm were used as highly sensitive real-time refractive index biosensors. Arrays of gold nanorings with tunable diameter, width, and spacing were created by the nanoscale electrodeposition of gold nanorings onto lithographically patterned nanohole array conductive surfaces over large areas (square centimeters). The bulk refractive index sensitivity of the gold nanoring arrays was determined to be up to 3,780 cm⁻¹/refractive index unit by monitoring shifts in the LSPR peak by FT-NIR transmittance spectroscopy measurements. As a first application, the surface polymerization reaction of dopamine to form polydopamine thin films on the nanoring sensor surface from aqueous solution was monitored with the real-time LSPR peak shift measurements. To demonstrate the utility of the gold nanoring arrays for LSPR biosensing, the hybridization adsorption of DNA-functionalized gold nanoparticles onto complementary DNA-functionalized gold nanoring arrays was monitored. The adsorption of DNA-modified gold nanoparticles onto nanoring arrays modified with mixed DNA monolayers that contained only 0.5 % complementary DNA was also detected; this relative surface coverage corresponds to the detection of DNA by hybridization adsorption from a 50 pM solution.

     

On‐target and nanoparticle‐facilitated selective enrichment of peptides and proteins for analysis by MALDI‐MS

Over the course of the last decade, a number of investigators have come to appreciate that the surface of a MALDI target, after suitable modification, can be used for selective enrichment of peptides and proteins. More recently, surface‐modified nanoparticles (NPs) that readily co‐crystallize in MALDI matrix, are not ionized by laser desorption/ionization, and do not interfere with MS have attracted interest as alternatives to surface‐modified targets for selective enrichment of peptides and proteins. Surface‐modified targets and NPs facilitate parallel processing of samples, and when used in conjunction with MALDI mass spectrometers with kHz lasers enable development of high‐throughput proteomics platforms. Targets and NPs for reversed phase and ion exchange retention, selective enrichment of glycopeptides, selective enrichment of phosphopeptides, and immunoaffinity MS are described in conjunction with details regarding their preparation and utility. Commercial availability of the reagents and substrates required to prepare surface‐modified targets and NPs is also discussed.     

Carbon‐Coated Si Nanoparticles Anchored between Reduced Graphene Oxides as an Extremely Reversible Anode Material for High Energy‐Density Li‐Ion Battery

Improving the lithium (Li) storage properties of silicon (Si)‐based anode materials is of great significance for the realization of advanced Li‐ion batteries. The major challenge is to make Si‐based anode materials maintain electronic conduction and structural integrity during cycling. Novel carbon‐coated Si nanoparticles (NPs)/reduced graphene oxides (rGO) composites are synthesized through simple solution mixing and layer‐by‐layer assembly between polydopamine‐coated Si NPs and graphene oxide nanosheets by filtration, followed by a thermal reduction. The anodic properties of this composite demonstrate the potency of the novel hybrid design based on two dimensional materials for extremely reversible energy conversion and storage. A high capacity and an extremely stable cycle life are simultaneously realized with carbon‐coated Si/rGO composite, which has a sandwich structure. The unprecedented electrochemical performance of this composite can be ascribed to the synergistic effect of polydopamine and rGO. The polydopamine layer forms strong hydrogen bonding with rGO through chemical cross‐linking, thus firmly anchoring Si NPs on rGO sheets to prevent the aggregation of Si NPs and their electronic contact loss. Finally, its structural feature with stacked rGO clipping carbon‐coated Si NPs inside it enables to keep the overall electrode highly conductive and mechanically robust, thus maintaining its initial capacity even with extended cycling.     

Molecular insights on the interference of simplified lung surfactant models by gold nanoparticle pollutants

Inhaled nanoparticles (NPs) are experienced by the first biological barrier inside the alveolus known as lung surfactant (LS), a surface tension reducing agent, consisting of phospholipids and proteins in the form of the monolayer at the air-water interface. The monolayer surface tension is continuously regulated by the alveolus compression and expansion and protects the alveoli from collapsing. Inhaled NPs can reach deep into the lungs and interfere with the biophysical properties of the lung components. The interaction mechanisms of bare gold nanoparticles (AuNPs) with the LS monolayer and the consequences of the interactions on lung function are not well understood. Coarse-grained molecular dynamics simulations were carried out to elucidate the interactions of AuNPs with simplified LS monolayers at the nanoscale. It was observed that the interactions of AuNPs and LS components deform the monolayer structure, change the biophysical properties of LS and create pores in the monolayer, which all interfere with the normal lungs function. The results also indicate that AuNP concentrations >0.1 mol% (of AuNPs/lipids) hinder the lowering of the LS surface tension, a prerequisite of the normal breathing process. Overall, these findings could help to identify the possible consequences of airborne NPs inhalation and their contribution to the potential development of various lung diseases.     

Zur Abbaubeschleunigung von Pflanzenschutzmittel-Wirkstoffen im Boden

In the current investigation, we report the biosynthesis of silver nanoparticles (Ag NPs) employing extract of Alternaria alternata, which is an eco-friendly process for the synthesis of metallic nanoparticles. Ag NPs were synthesised through the reduction of aqueous Ag⁺ ion using the cell extract of fungus A. alternata in the dark conditions. The synthetic process was relatively fast and Ag NPs were formed within 24 h. UV–visible spectrum of the aqueous medium containing silver ion showed a peak at 435?nm corresponding to the plasmon absorbance of Ag NPs and another peak at 280?nm refers to tyrosine amino acid. The nanoparticles were characterised by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The morphology of nanoparticles is found to be spherical mostly, with ranging size of 27–79?nm; as revealed by SEM. The FTIR spectrum analysis indicated that biomolecules were involved in the synthesis of Ag NPs. The presence of the amino groups is expected to pack differently around the Ag NPs. This in turn will influence the self-assembly of nanoparticles on substrates as well as their stability. The present study demonstrates the possible use of biologically synthesised Ag NPs in the field of agriculture, when A. alternata could be used for simple, nonhazardous and efficient synthesis of Ag NPs.     

Inorganic nanoparticle-based contrast agents for molecular imaging

Inorganic nanoparticles (NPs) including semiconductor quantum dots (QDs), iron oxide NPs and gold NPs have been developed as contrast agents for diagnostics by molecular imaging. Compared with traditional contrast agents, NPs offer several advantages: their optical and magnetic properties can be tailored by engineering the composition, structure, size and shape; their surfaces can be modified with ligands to target specific biomarkers of disease; the contrast enhancement provided can be equivalent to millions of molecular counterparts; and they can be integrated with a combination of different functions for multimodal imaging. Here, we review recent advances in the development of contrast agents based on inorganic NPs for molecular imaging, and also touch on contrast enhancement, surface modification, tissue targeting, clearance and toxicity. As research efforts intensify, contrast agents based on inorganic NPs that are highly sensitive, target-specific and safe to use are expected to enter clinical applications in the near future.     

Glycol chitosan/heparin immobilized iron oxide nanoparticles with a tumor-targeting characteristic for magnetic resonance imaging

We described the preparation of the glycol chitosan/heparin immobilized iron oxide nanoparticles (composite NPs) as a magnetic resonance imaging agent with a tumor-targeting characteristic. The iron oxide nanoseeds used clinically as a magnetic resonance imaging agent were immobilized into the glycol chitosan/heparin network to form the composite NPs. To induce the ionic interaction between the iron oxide nanoseeds and glycol chitosan, gold was deposited on the surface of iron oxide nanoseeds. After the immobilization of gold-deposited iron oxide NPs into the glycol chitosan network, the NPs were stabilized with heparin based on the ionic interaction between cationic glycol chitosan and anionic heparin. FE-SEM (field emission-scanning electron microscopy) and a particle size analyzer were used to observe the formation of the stabilized composite NPs, and a Jobin-Yvon Ultima-C inductively coupled plasma-atomic emission spectrometer (ICP-AES) was used to measure the contents (%) of formed iron oxide nanoseeds as a function of reaction temperature and formed gold deposited on the iron oxide nanoparticles. We also evaluated the time-dependent excretion profile, in vivo biodistribution, circulation time, and tumor-targeting ability of the composite NPs using a noninvasive NIR fluorescence imaging technology. To observe the MRI contrast characteristic, the composite NPs were injected into the tail veins of tumor-bearing mice to demonstrate their selective tumoral distribution. The MR images were collected with conventional T(2)-weighted spin echo acquisition parameters.     

Surface-modified magnetite nanoparticles affect lysozyme amyloid fibrillization

BackgroundThe surface of nanoparticles (NPs) is an important factor affecting the process of poly/peptides' amyloid aggregation. We have investigated the in vitro effect of trisodium citrate (TC), gum arabic (GA) and citric acid (CA) surface-modified magnetite nanoparticles (COAT-MNPs) on hen egg-white lysozyme (HEWL) amyloid fibrillization and mature HEWL fibrils.MethodsDynamic light scattering (DLS) was used to characterize the physico-chemical properties of studied COAT-MNPs and determine the adsorption potential of their surface towards HEWL. The anti-amyloid properties were studied using thioflavin T (ThT) and tryptophan (Trp) intrinsic fluorescence assays, and atomic force microscopy (AFM). The morphology of amyloid aggregates was analyzed using Gwyddion software. The cytotoxicity of COAT-MNPs was determined utilizing Trypan blue (TB) assay.ResultsAgents used for surface modification affect the COAT-MNPs physico-chemical properties and modulate their anti-amyloid potential. The results from ThT and intrinsic fluorescence showed that the inhibitory activities result from the more favorable interactions of COAT-MNPs with early pre-amyloid species, presumably reducing nuclei and oligomers formation necessary for amyloid fibrillization. COAT-MNPs also possess destroying potential, which is presumably caused by the interaction with hydrophobic residues of the fibrils, resulting in the interruption of an interface between β-sheets stabilizing the amyloid fibrils.ConclusionCOAT-MNPs were able to inhibit HEWL fibrillization and destroy mature fibrils with different efficacy depending on their properties, TC-MNPs being the most potent nanoparticles.General significanceThe study reports findings regarding the general impact of nanoparticles' surface modifications on the amyloid aggregation of proteins.     

Aptamer–Au NPs conjugates-enhanced SPR sensing for the ultrasensitive sandwich immunoassay

The goal of this work is to explore the amplification effect of aptamer–gold nanoparticles (Au NPs) conjugates for ultrasensitive detection of large biomolecules by surface plasmon resonance (SPR). A novel sandwich immunoassay is designed to demonstrate the amplification effect of aptamer–Au NPs conjugates by using human immunoglobulin E (IgE) as model analyte. Human IgE, captured by immobilized goat anti-human IgE on SPR gold film, is sensitively detected by SPR spectroscopy with a lowest detection limit of 1 ng/ml after anti-human IgE aptamer–Au NPs conjugates is used as amplification reagent. Meanwhile, the non-specific adsorption of aptamer–Au NPs conjugates on goat anti-human IgE is confirmed by SPR spectroscopy and then it is minimized by treating aptamer–Au NPs conjugates with 6-mercaptohexan-1-ol (MCH). These results confirm that aptamer–Au NPs conjugates is a powerful sandwich element and an excellent amplification reagent for SPR-based sandwich immunoassay.     

Microbial Synthesis of Nanoparticles: Mechanisms,Characteristics, and Applications

Cadmium sulfide (CdS) and zinc sulfide (ZnS) biogenic nanoparticles (NPs) were produced by microbial synthesis using bacteria of different taxonomic groups: Gram-negative (Shewanella oneidensis MR-1) and Gram-positive (Bacillus subtilis 168) bacteria in a liquid medium under aerobic conditions in the presence of salts of the respective metals and sulfur. It was shown that the stabilization of nanoparticles in aqueous suspensions is due to the presence of certain protein molecules of the outer membrane of cells, that is, proteins of the families of various receptors, porins, and flagellin, on the nanoparticle (NP) surface. The effect of the protein coating on stability, luminescence, zeta-potential, hydrodynamics diameter and other physiochemical characteristics of nanoparticles was studied. Decolorization of methylene blue dye under the exposure to UV irradiation was used as a model to demonstrate the photocatalytic properties of NPsCdS. This opens the possibility of using biogenic nanoparticles in photocatalysis for industrial wastewater treatment.

     

Vapor Phase Deposition, Structure, and Plasmonic Properties of Polymer-Based Composites Containing Ag–Cu Bimetallic Nanoparticles

Nanocomposite (NC) thin films with noble metal nanoparticles embedded in a dielectric material show very attractive plasmonic properties due to dielectric and quantum confinement effects. For single component nanoparticles (NPs), the plasmon resonance frequency can only be tuned in a narrow range. Much interest aroused in bimetallic nanoparticles (BNPs), however many wet chemical approaches do not allow large variation of the NP alloy composition and filling factor. Here, we report a vapor phase co-deposition method to produce polymer–metal NCs with embedded Ag_1 − x Cu _x alloy particles. The method allows production of NPs with controlled alloy composition (x), metal filling (f) and nanostructure in a protecting Teflon AF matrix. The nanostructure size and shape were characterized by transmission electron microscope. Energy dispersive X-ray spectroscopy was used to determine x and f. The optical properties and the position of surface plasmon resonances were studied by UV–Vis spectroscopy. The plasmon resonances can be tuned over a large range of the visible spectrum associated with the change in x, f, and nanostructure. For low filling factors and small particle sizes, only one resonance peak was observed. This is attributed to enhanced miscibility at the nanoscale. Double plasmon resonances were seen for larger particle sizes in accord with phase separation expected from the bulk phase diagram and were explained in terms of the formation of core-shell structures with Cu core and Ag shell. Changes upon annealing at 200 °C are also reported.     

Addressable self-immobilization of lactate dehydrogenase across multiple length scales

Successful nanobiotechnology implementation largely depends on control over the interfaces between inorganic materials and biological molecules. Controlling the orientations of biomolecules and their spatial arrangements on the surface may transform many technologies including sensors, to energy. Here, we demonstrate the self-organization of L -lactate dehydrogenase (LDH), which exhibits enhanced enzymatic activity and stability on a variety of gold surfaces ranging from nanoparticles to electrodes, by incorporating a gold-binding peptide tag (AuBP2) as the fusion partner for Bacillus stearothermophilus LDH (bsLDH). Binding kinetics and enzymatic assays verified orientation control of the enzyme on the gold surface through the genetically incorporated peptide tag. Finally, redox catalysis efficiency of the immobilized enzyme was detected using cyclic voltammetry analysis in enzyme-based biosensors for lactate detection as well as in biofuel cell energy systems as the anodic counterpart. Our results demonstrate that the LDH enzyme can be self-immobilized onto different gold substrates using the short peptide tag under a biologically friendly environment. Depending on the desired inorganic surface, the proposed peptide-mediated path could be extended to any surface to achieve single-step oriented enzyme immobilization for a wide range of applications.     

Structural characterization,antioxidant and anticancer properties of gold nanoparticles synthesized from leaf extract (decoction) of Antigonon leptopus Hook. & Arn.

Tea is an aromatic beverage prepared by pouring boiling water over alleviated leaves of the tea plant. Tea prepared from the aerial parts of Antigonon leptopus has been traditionally used as remedy for cold, diabetes and pain in many countries. The gold nanoparticles (Au NPs) synthesized from powdered leaf extract (decoction) of A. leptopus were characterized by UV–visible spectroscopy (UV–vis), X-ray diffraction (XRD), Fourier transform-infrared (FT-IR), high resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED) pattern and energy dispersive X-ray (EDX) analyses to define the formation of Au NPs. Further, the synthesized Au NPs were well characterized based on their strong surface plasmon resonance (SPR), crystalline nature, functional groups, size and dispersed shapes, purity and Bragg's reflections of face centered cubic (fcc) structure of metallic gold. The Au NPs showed higher free radical scavenging property when compared to the effect of leaf extract. Cytotoxicity study of synthesized Au NPs exhibited the growth inhibitory property at the concentration (GI₅₀) of 257.8 μg/mL in human adenocarcinoma breast cancer (MCF-7) cells after 48 h. Thus, the Au NPs synthesized from the Mexican creeper, A. leptopus revealed the important biological properties: as a free radical as well as anticancer agent. We conclude that the A. leptopus derived biological materials have promising potential as a source for the development of anticancer drug in future.     

Synthesis of Silver and Gold Nanoparticles Using Cashew Nut Shell Liquid and Its Antibacterial Activity Against Fish Pathogens

This study reveals a green process for the production of multi-morphological silver (Ag NPs) and gold (Au NPs) nanoparticles, synthesized using an agro-industrial residue cashew nut shell liquid. Aqueous solutions of Ag⁺ ions for silver and chloroaurate ions for gold were treated with cashew nut shell extract for the formation of Ag and Au NPs. The nano metallic dispersions were characterized by measuring the surface plasmon absorbance at 440 and 546 nm for Ag and Au NPs. Transmission electron microscopy showed the formation of nanoparticles in the range of 5–20 nm for silver and gold with assorted morphologies such as round, triangular, spherical and irregular. Scanning electron microscopy with energy dispersive spectroscopy and X-ray diffraction analyses of the freeze-dried powder confirmed the formation of metallic Ag and Au NPs in crystalline form. Further analysis by Fourier transform infrared spectroscopy provided evidence for the presence of various biomolecules, which might be responsible for the reduction of silver and gold ions. The obtained Ag and Au NPs had significant antibacterial activity, minimum inhibitory concentration and minimum bactericidal concentration on bacteria associated with fish diseases.     

Antioxidant and antibacterial activities of eugenol and carvacrol‐grafted chitosan nanoparticles

Essential oils are known to possess antimicrobial and antioxidant activity while chitosan is a biocompatible polymer with antibacterial activity against a broad spectrum of bacteria. In this work, nanoparticles with both antioxidant and antibacterial properties were prepared by grafting eugenol and carvacrol (two components of essential oils) on chitosan nanoparticles. Aldehyde groups were first introduced in eugenol and carvacrol, and the grafting of these oils to chitosan nanoparticles was carried out via the Schiff base reaction. The surface concentration of the grafted essential oil components was determined by X‐ray photoelectron spectroscopy (XPS). The antioxidant activities of the carvacrol‐grafted chitosan nanoparticles (CHCA NPs) and the eugenol‐grafted chitosan nanoparticles (CHEU NPs) were assayed with diphenylpicrylhydrazyl (DPPH). Antibacterial assays were carried out with a representative gram‐negative bacterium, Escherichia coli (E. coli) and a gram‐positive bacterium, Staphylococcus aureus (S. aureus). The grafted eugenol and carvacrol conferred antioxidant activity to the chitosan nanoparticles, and the essential oil component‐grafted chitosan nanoparticles achieved an antibacterial activity equivalent to or better than that of the unmodified chitosan nanoparticles. Cytotoxicity assays using 3T3 mouse fibroblast showed that the cytotoxicity of CHEU NPs and CHCA NPs were significant lower than those of the pure essential oils. Biotechnol. Bioeng. 2009; 104: 30–39 © 2009 Wiley Periodicals, Inc.     

Fine-Tuning the Antimicrobial Profile of Biocompatible Gold Nanoparticles by Sequential Surface Functionalization Using Polyoxometalates and Lysine

Antimicrobial action of nanomaterials is typically assigned to the nanomaterial composition, size and/or shape, whereas influence of complex corona stabilizing the nanoparticle surface is often neglected. We demonstrate sequential surface functionalization of tyrosine-reduced gold nanoparticles (AuNPs^Tyr) with polyoxometalates (POMs) and lysine to explore controlled chemical functionality-driven antimicrobial activity. Our investigations reveal that highly biocompatible gold nanoparticles can be tuned to be a strong antibacterial agent by fine-tuning their surface properties in a controllable manner. The observation from the antimicrobial studies on a gram negative bacterium Escherichia coli were further validated by investigating the anticancer properties of these step-wise surface-controlled materials against A549 human lung carcinoma cells, which showed a similar toxicity pattern. These studies highlight that the nanomaterial toxicity and biological applicability are strongly governed by their surface corona.     

Direct Fabrication Route to Plastic-Supported Gold Nanoparticles for Flexible NIR-SERS

Stable gold nanoparticles with surface plasmon resonance tunable from visible (Vis) to near-infrared (NIR) are deposited via a direct sputtering methodology on large area polyethylene terephthalate (PET) to be used as effective, flexible NIR surface-enhanced Raman scattering (SERS) substrates. An O₂ plasma treatment of PET is used to tailor growth dynamics, geometry, and plasmonic properties of nanoparticles. The O₂ plasma treatment of PET results also in effective improvement of nanoparticle anchoring on the plastic substrate, providing more stable, flexible SERS systems. The functionality of fabricated SERS substrates has been tested using benzylthiol, and SERS enhancement factors in the range 10⁴ have been achieved, which are comparable with those reported in literature for gold nanostructures fabricated on silicon substrate. These results attest the great potentiality of this methodology for the production of cost-effective flexible and reusable large-scale SERS substrates.     

Transfecting pDNA to E. coli DH5α using bovine serum albumin nanoparticles as a delivery vehicle

We describe the formulation of bovine serum albumin nanoparticles (BSA‐NPs) by the coacervation method using surfactants. Plasmids (pUC18, pUC18egfp and pBBR1MCS‐2) isolated from E. coli were incorporated into the BSA matrix by incubating in albumin solution prior to formulation of NPs. Plasmid incorporation was calculated by % yield, entrapment efficiency, DNA loading capacity and release of entrapped DNA by comparing with blank NPs. BSA‐DNA binding studies were carried out by using fluorescence spectroscopy and Fourier Transform Infra Red Spectroscopy (FT‐IR). The surface charge distribution of the NPs loaded with plasmid was calculated using zeta potential. The photoluminescence of BSA‐NPs was quenched when loaded with pDNA, confirming the interaction of DNA with BSA. Altogether, these results provide evidences for the excellent DNA carrying efficiency of BSA‐NPs without loss of plasmid's integrity. The NPs were used to transfect E. coli DH5α strain lacking ampicillin resistance. They, however, showed ampicillin resistance subsequent to transfection with plasmid encoding ampicillin resistance gene. Effect of transfection was confirmed by confocal microscopy and by the isolation of the plasmid by agarose gel electrophoresis from the transfected bacterial culture. This study clearly demonstrates the efficacy of BSA‐NPs as delivery vehicle for pDNA transfection. Copyright © 2014 John Wiley & Sons, Ltd.