Ultrasensitive detection of biomolecules with fluorescent dye-doped nanoparticles

Detection of HPV-16 by a Simple and Cost-Effective DNA Probe: Polyadenine-Polythymine-Decorated Gold Nanoparticles (PolyA-PolyT@AuNPs)

HPV-16 identification is crucial for point-of-care molecular diagnosis of cervical cancer. However, the diagnostic methods currently in use are unable to combine both high analytical performance and cost-efficient medical diagnosis. To circumvent this, we have developed a novel nanobiosensor for diagnosis of the HPV-16 L1 gene sequence through colorimetric methods. Using a unique conjugation technique of polyvalent DNA to gold nanoparticles (AuNPs), quickly synthesizing AuNPs synthesis in situ at the particular probe-polyadenine-polythymine (A15-T10) strands was developed. Transmission electron microscopy (TEM), dynamic light scattering (DLS), gel electrophoresis, UV-Vis spectroscopy, and visual detection demonstrate that the Poly(A)15-(T)10 strand can create separate anisotropic AuNPs so that a thick layer of DNA is functionalized on each AuNP, therefore generating polyvalent (p)DNA-AuNPs. Moreover, the hybridization test, UV-Vis spectroscopy, TEM, visual detection, and DLS results further confirmed the innovative sensing applicability, showing more excellent attractiveness of pDNA-AuNPs conjugation in diagnostics in biomedicine and particular sequence detection, such as double-stranded DNA (dsDNA) by employing probe-polyA-polyT extra-strands that are in harmony with the intended sequence. This sensor demonstrated good performance levels with a sensitivity of up to 1.9 nM for pUCm-T. Additionally, the sensor showed intense discrimination against actual clinically collected HPV-16 samples, consistent stability, and good repeatability.

Fluorescent silica nanoparticles as an internal marker in fruit flies and their effects on survivorship and fertility

Tracking and differentiating small insects at the individual levels requires appropriate marking materials because of their small size. This study proposes and investigates the use of fluorescent silica nanoparticles (FSNPs) as an internal marker owing to their good optical properties and biocompatibility. FSNPs were prepared using the water-in-oil reverse microemulsion technique with Rubpy dye as a fluorophore. The obtained particles were spherical, monodispersed in nanosize and exhibited bright orange luminescence under ultraviolet (UV) light. Internal marking was accomplished in fruit flies (Drosophila melanogaster) through feeding. The result shows that the fruit flies exhibit bright luminescence in their abdomen when exposed to UV light. The marking persistence duration of FSNPs in the fruit fly bodies is longer than those of other fluorescent dyes. Fruit flies fed with FSNPs have a longer lifespan than those fed with Rubpy dye. There was no difference in fertility and negative geotaxis response among the treatment and control groups. These findings demonstrate that FSNPs can be used as an internal marker in fruit flies, and are possibly applied with other small insects with a translucent abdomen.

Optimized antibody immobilization on natural silica-based nanostructures for the selective detection of E. coli

This study reports for the first time the surface modification of fluorescent nanoparticles derived from geothermal silica precipitate with Escherichia coli (E. coli) antibody. The immobilization of biomolecules on the inorganic surface has been carried out using two different pathways, namely the silanization and hydrosilylation reactions. The former applied (3-aminopropyl)triethoxysilane (APTES) as the crosslinker, while the latter used N-hydroxysuccinimide coupled with N-ethyl-N'-(3-dimethyl aminopropyl) carbodiimide hydrochloride (EDC/NHS). Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy with energy dispersive X-ray spectroscopy (FESEM-EDX), and fluorescence spectroscopy were used to confirm the chemical, physical, and optical properties of the surface-modified fluorescent silica nanoparticles (FSNPs). Based on the results of the FTIR, fluorescence spectroscopy and stability tests, the modified FSNPs with EDC/NHS with a ratio of 4 : 1 were proven to provide the optimum results for further conjugation with antibodies, affording the FSNP-Ab2 sample. The FSNP-Ab2 sample was further tested as a nanoplatform for the fluorescence-quenching detection of E. coli, which provided a linear range of 102 to 107 CFU mL-1 for E. coli with a limit of detection (LoD) of 1.6 × 102 CFU mL-1. The selectivity of the biosensor was observed to be excellent for E. coli compared to that for P. aeruginosa and S. typhimurium, with reductions in the maximum fluorescence intensity at 588 nm of 89.22%, 26.23%, and 54.06%, respectively. The inorganic nanostructure-biomolecule conjugation with optimized coupling agents showed promising analytical performance as a selective nanoplatform for detecting E. coli bacteria.

Application of "smart" multifunctional nanoprobes in tumor diagnosis and treatment

Cancer is one of the major diseases that pose a threat to human health and life, especially because it is difficult to diagnose and cure, and recurs easily. In recent years, the development of nanotechnology has provided researchers with new tools for cancer treatment. In particular, nanoprobes that facilitate integrated diagnosis and treatment, high-resolution imaging, and accurate tumor targeting provide new avenues for the early detection and treatment of cancer. This review focuses on the preparations and applications of two kinds of "smart" multifunctional nanoprobes: "Off-On" nanoprobes and "Charge-Reversal" nanoprobes. This review also briefly discusses their mechanisms of action, as they could provide new ideas for the further development of this field.

Covalent binding of glutathione on magnetic nanoparticles: Application for immobilizing small fragment ubiquitin-like-specific protease 1

Magnetic nanoparticles bound with glutathione (GSH) are useful for diagnostics, enzyme immobilization, and affinity precipitation by using the strong and specific interaction of GSH with glutathione S-transferase (GST)-fused proteins. Our studies revealed that GSH-bound magnetic nanoparticles could be obtained using the covalent bond linkage of GSH and nanoparticles to promote the stability of bound GSH. To yield this conjugate, superparamagnetic iron oxide nanoparticles (SPIONs) were prepared and modified using tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES), which introduced amino groups that were then activated with maleic anhydride (MA) for covalent binding of GSH. After MA was used to activate the amino-grafted SPION for 24 h, the yield of GSH conjugation increased over 4 days from 37 % to 74 % of the original amine density on the surface as the incubation of GSH with MA-activated SPION. These GSH-bound magnetic nanoparticles, designated as SPION@silica-GSH with approximately 103 nmol GSH/mg particles, were ready for coupling with GST-fused protein through the GSH-GST affinity interaction. A GST-tagged small fragment of ubiquitin-like-specific protease 1 (sfULP1) was used as the model protein for immobilization on SPION@silica-GSH. ULP1 is a small ubiquitin-like modifier (SUMO) protease. Results indicated that this immobilized GST-sfULP1 could retain 87 % ± 5 % enzyme activity of free protease before immobilization and could catalyze the cleavage of the SUMO-fused peptide (SUMO-GLP-1) to obtain glucagon-like peptide-1, a peptide hormone for type 2 diabetes therapy.

Synthetic Tuning of CoII-Doped Silica Nanoarchitecture Towards Electrochemical Sensing Ability

The present work introduces both synthesis of silica nanoparticles doped with CoII ions by means of differently modified microemulsion water-in-oil (w/o) and Stöber techniques and characterization of the hybrid nanoparticles (CoII@SiO2) by TEM, DLS, XRD, ICP-EOS, SAXS, UV-Vis, and UV-Vis/DR spectroscopy and electrochemical methods. The results reveal the lack of nanocrystalline dopants inside the hybrid nanoparticles, as well as no ligands, when CoII ions are added to the synthetic mixtures as CoII(bpy)3 complexes, thus pointing to coordination of CoII ions with Si-O- groups as main driving force of the doping. The UV-Vis/DR spectra of CoII@SiO2 in the range of d-d transitions indicate that Stöber synthesis in greater extent than the w/o one stabilizes tetrahedral CoII ions versus the octahedral ions. Both cobalt content and homogeneity of the CoII distribution within CoII@SiO2 are greatly influenced by the synthetic technique. The electrochemical behavior of CoII@SiO2 is manifested by one oxidation and two reduction steps, which provide the basis for electrochemical response on glyphosate and HP(O)(OEt)2 with the LOD = 0.1 μM and the linearity within 0.1-80 μM. The Stöber CoII@SiO2 are able to discriminate glyphosate from HP(O)(OEt)2, while the w/o nanoparticles are more efficient but nonselective sensors on the toxicants.

Biologically synthesized ZnS quantum dots as fluorescent probes for lead (II) sensing

This manuscript presents a robust strategy for selective Pb(II) sensing based on a fluorescence turn-off mechanism using ZnS quantum dots (QDs) biosynthesized using Aspergillus sp. The biogenic nanoprobe displayed marked sensing efficiency in the presence of Pb ions over concentration ranges from 5 to 100 μM with limits of detection of around 2.45 μM. Performance optimization studies revealed that the maximum fluorescence quenching efficiency was obtained in the presence of [ZnS NPs] at 4 mg/ml, and alkaline pH of 10 recorded under stable ambient temperature for approximately 5 min for the quenching process. Advanced morphological analysis indicated that the bio-sensing mechanism was essentially a surface-based phenomenon in which the Pb ions were in very close proximity to the QDs and formed stable ground-state Pb-ZnS complexes, resulting in a quenched fluorescence of the QDs. Simultaneously, a larger fraction of Pb ions interacted via collisions with the excited ZnS QDs and resulted in an effective energy transfer from the excited QDs to the Pb ions, therefore resulting in an obvious decrease in QD fluorescence. These insights were well supported by theoretical analysis using Stern-Volmer plots and sphere-of-action models.

Exposure of CuO Nanoparticles Contributes to Cellular Apoptosis, Redox Stress, and Alzheimer's Aβ Amyloidosis

Fe2O3, CuO and ZnO nanoparticles (NP) have found various industrial and biomedical applications. However, there are growing concerns among the general public and regulators about their potential environmental and health impacts as their physio-chemical interaction with biological systems and toxic responses of the latter are complex and not well understood. Herein we first reported that human SH-SY5Y and H4 cells and rat PC12 cell lines displayed concentration-dependent neurotoxic responses to insults of CuO nanoparticles (CuONP), but not to Fe2O3 nanoparticles (Fe2O3NP) or ZnO nanoparticles (ZnONP). This study provides evidence that CuONP induces neuronal cell apoptosis, discerns a likely p53-dependent apoptosis pathway and builds out the relationship between nanoparticles and Alzheimer's disease (AD) through the involvement of reactive oxygen species (ROS) and increased Aβ levels in SH-SY5Y and H4 cells. Our results implicate that exposure to CuONP may be an environmental risk factor for AD. For public health concerns, regulation for environmental or occupational exposure of CuONP are thus warranted given AD has already become a pandemic.

Designing a nanoparticle-containing polymeric substrate for detecting cancer cells by computer simulations

Efficient and accurate detection of cancer cells (from normal cells) is of great importance in cancer diagnosis and prognosis. In this work, we design a new type of polymeric substrate containing nanoparticles for detecting cancers by the dissipative particle dynamics (DPD) simulation. It is found that the cancer cells and the normal cells can be indeed distinguished since the uptake number of nanoparticles from the substrate is different. The competition between the nanoparticle-cell specific interaction and nanoparticle-polymer non-specific interaction is the main factor for different uptake behaviors. Moreover, the dynamics of the nanoparticle diffusion in the polymer layer also plays an important role in the detection. To improve the detection accuracy, we further investigate the effect of the polymer type and density as well as the ligand type on the detection, and find that there may exist an optimal parameter to maximize the difference between cancer cells and normal cells. The present study may provide useful insights into the design of functionalized substrate-based nanodevices in biomedicine.

Engineered nanomaterials and human health: Part 1. Preparation, functionalization and characterization (IUPAC Technical Report)

Nanotechnology is a rapidly evolving field, as evidenced by the large number of publications on the synthesis, characterization, and biological/environmental effects of new nano-sized materials. The unique, size-dependent properties of nanomaterials have been exploited in a diverse range of applications and in many examples of nano-enabled consumer products. In this account we focus on Engineered Nanomaterials (ENM), a class of deliberately designed and constructed nano-sized materials. Due to the large volume of publications, we separated the preparation and characterisation of ENM from applications and toxicity into two interconnected documents. Part 1 summarizes nanomaterial terminology and provides an overview of the best practices for their preparation, surface functionalization, and analytical characterization. Part 2 (this issue, Pure Appl. Chem. 2018; 90(8): 1325–1356) focuses on ENM that are used in products that are expected to come in close contact with consumers. It reviews nanomaterials used in therapeutics, diagnostics, and consumer goods and summarizes current nanotoxicology challenges and the current state of nanomaterial regulation, providing insight on the growing public debate on whether the environmental and social costs of nanotechnology outweigh its potential benefits.

Physisorption and chemisorption of T4 bacteriophages on amino functionalized silica particles

Bacteriophages, or phages, are receiving increasing interest as recognition tools for the design of bioactive surfaces. However, to maintain the activity of surface-bound phages, the immobilization strategy must provide the right orientation and not compromise the phages' integrity. The objectives of this study were to characterize the phage sorption capacity and the immobilized phage activity for aminated silica particles functionalized with T4 phages. Two functionalization strategies were compared; physisorption, based on electrostatic adhesion, and chemisorption, where the phage and the particle are coupled using a carbodiimide cross-linker. We report that chemisorption, at maximum adsorption conditions on 1 µm particles, yielded 16 functional phages per particle, which is 2.5 times more than by the physisorption method. Particle diameter is shown to have an important impact on phage attachment and 1.8 µm particles were found to have ∼4 times more phages per surface area than 0.5 µm particles. Higher surface coverage is attributed to the lower steric hindrance on bigger particles. These findings provide important guidelines for the design of phage-functionalized particles for environmental, biomedical, or sensing applications.

Multicolored Protein Nanoparticles: Synthesis, Characterization, and Cell Uptake

Synthesis, characterization, and applications of strongly fluorescent, multicolored protein nanoparticles (GlowDots) are reported here. Bovine serum albumin was cross-linked under controlled conditions to form nanoparticles, where particle size was controlled from 20 to 100 ± 10 nm by choosing appropriate reaction conditions. The absorption as well as the emission wavelengths were controlled without changing the particle size, unlike quantum dots. Each GlowDot was loaded with up to 214 ± 50 chromophores, and hence, the particles have high molar absorptivities (10⁶ M^-1 cm^-1) as well as high brightness (10⁵ to 10⁶ M^-1 cm^-1). A large number of functional groups cover the particle surface and these are further functionalized to enhance cellular uptake. GlowDots that were labeled with fluorescein and functionalized with taurine, for example, were quickly taken up by HeLa, MDA-MB-231, PC3, and L6 myoblast cells, as interrogated by fluorescence imaging studies. GlowDots were biocompatible, size tunable, biodegradable, strongly fluorescent, and stable for months at room temperature, and they may serve as substitutes for quantum dots in a variety of practical applications.

Preparation of fluorescently labeled silica nanoparticles using an amino acid-catalyzed seeds regrowth technique: Application to latent fingerprints detection and hemocompatibility studies

The efficiency of an amino acid catalyzed seed regrowth technique (ACSRT) in synthesizing twelve fluorescently labeled core-shell silica nanoparticles (FLSNPs) with tunable sizes, tailored hydrophobicity, low polydispersity as well as high labeling efficiency and minimized dye leakage using different combinations of organosilicate monomers and fluorophores have been systematically investigated in this report. The utilization of some of these FLSNPs in some applications that are facilitated by hydrophobicity such as developing and visualizing latent fingerprints (LFPs) on different surfaces was also investigated. The non-specific binding affinity of the developed nanoparticles to human serum albumin (HSA) and immunoglobulin G (IgG) has also been studied. Fluorescein, fluorescein isothiocyanate and its more hydrophilic butenamine derivative (WA6) have been used in this study. Also, the alkoxysilane precursor, tetraethoxyorthosilicate (TEOS) and its binary mixture with phenyltriethoxysilane (PTEOS) or 3-aminopropyl triethoxysilane (APTES) have been used in preparing the FLSNPs with tailored compositions for the core and shell of the nanoparticles. The mean diameters of the PTEOS-coated FLSNPs were between 33.4±5.9 and 42.2±10.8 nm as shown by the SEM measurements. The obtained results highlight the advantages of having a hydrophobic surface along with proper selection of the monomers forming the core to match the properties of the fluorescent reporters for clear detection of LFPs even using dyes of low hydrophobicity such as fluorescein and WA6. Furthermore, some of the developed FLSNPs were compared with bare silica nanoparticles in terms of nonspecific protein adsorption and hemolysis. The obtained results proved that the selected FLSNPs had a superior hemocompatibility in comparison with bare silica nanoparticles. These FLSNPs could also be used in some bio-related and diagnostic applications such as immunoassays and cell imaging purposes.

Optimization of gold nanoparticle-based real-time colorimetric assay of dipeptidyl peptidase IV activity

Dipeptidyl peptidase IV (DPP-IV also referred to as CD-26) is a serine protease enzyme with remarkable diagnostic and prognostic value in a variety of health and disease conditions. Herein, we describe a simple and real-time colorimetric assay for DPP-IV/CD-26 activity based on the aggregation of gold nanoparticles (AuNPs) functionalized with the peptide substrates: Gly-Pro-Asp-Cys (GPDC) or Val-Pro-ethylene diamine-Asp-Cys (VP-ED-DC). Cleavage of the substrates by DPP-IV resulted in aggregation of the AuNPs with accompanying color change in the solution from red to blue that was monitored using either a UV-visible spectrophotometer or by the naked eye. Factors, such as time course of the reaction, stability of the functionalized AuNPs and the structure of the substrate that influence the cleavage reaction in solution were investigated. The effects of potential interference from serum proteins (lysozyme, thrombin and trypsin) on the analytical response were negligible. The detection limits when GPDC or VP-EN-DC functionalized AuNPs were used for DPP-IV assay were 1.2U/L and 1.5U/L, respectively. The VP-EN-DC method was preferred for the quantitative determination of DPP-IV activity in serum because of its wide linear range 0-30U/L compared to 0-12U/L for the GPDC assay. Recoveries from serum samples spiked with DPP-IV activity, between 5 and 25U/L, and using the VP-EN-DC modified AuNPs method ranged between 83.6% and 114.9%. The two colorimetric biosensors described here are superior to other conventional methods because of their simplicity, stability, selectivity and reliability.

Bioprobes Based on Aptamer and Silica Fluorescent Nanoparticles for Bacteria Salmonella typhimurium Detection

In this study, we have developed an efficient method based on single-stranded DNA (ssDNA) aptamers along with silica fluorescence nanoparticles for bacteria Salmonella typhimurium detection. Carboxyl-modified Tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate (RuBPY)-doped silica nanoparticles (COOH-FSiNPs) were prepared using reverse microemulsion method, and the streptavidin was conjugated to the surface of the prepared COOH-FSiNPs. The bacteria S. typhimurium was incubated with a specific ssDNA biotin-labeled aptamer, and then the aptamer-bacteria conjugates were treated with the synthetic streptavidin-conjugated silica fluorescence nanoprobes (SA-FSiNPs). The results under fluorescence microscopy show that SA-FSiNPs can be applied effectively for the labeling of bacteria S. typhimurium with great photostable property. To further verify the specificity of SA-FSiNPs out of multiple bacterial conditions, variant concentrations of bacteria mixtures composed of bacteria S. typhimurium, Escherichia coli, and Bacillus subtilis were treated with SA-FSiNPs.In addition, the feasibility of SA-FSiNPs for bacteria S. typhimurium detection in chicken samples was assessed. All the results display that the established aptamer-based nanoprobes exhibit the superiority for bacteria S. typhimurium detection, which is referentially significant for wider application prospects in pathogen detection.

Ultrasensitive microarray bioassays using cyanine5 dye-doped silica nanoparticles

Herein we report the use of high brightness Cyanine5-doped silica nanoparticles (NPs) for the detection of antibodies or DNA in microarray bioassays. NP labels showed negligible non-specific binding, greater sensitivity and lower limits of detection when compared to free dye-labelled biomolecules. Moreover, the spotted microarrays used in this study required low NP and antibody concentrations to generate large data sets with improved statistical accuracy. These NPs have significant potential for use in biosensing for disease detection.

Synthesis and stability of IR-820 and FITC doped silica nanoparticles

Fluorescent silica nanoparticles (NPs) have potential in biomedical applications as diagnostics and traceable drug delivery agents. In this study, we have synthesized fluorescent dye grafted silica NPs in two step process. First, a stable method to synthesize various sizes of silica NPs ranging from 20 to 52, 95, 210 and 410nm have been successfully demonstrated. Secondly, as-synthesized silica NPs are readily grafted with some fluorescent dyes like IR-820 and fluorescein isothiocyanate (FITC) dyes by simple impregnation method. IR-820 and FITC dyes are 'activated' by (3-mercaptopropyl)trimethoxysilane (MPTMS) and (3-aminopropyl)triethoxysilane (APTS) respectively prior to the grafting on silica NPs. UV-vis spectroscopy is used to test the stability of dye grafted silica NPs. The fluorescent dye grafted silica NPs are quite stable in aqueous solution. Also, a new type of dual dye-doped hybrid silica nanoparticles has been developed. The combination of microscopic and spectroscopic techniques shows that the synthesis parameters have significant effects on the particle shape and size and is tuneable from a few nanometers to a few hundred nanometers. The ability to create size controlled nanoparticles with associated (optical) functionality may have significant importance in bio-medical imaging.

A direct detection of human papillomavirus 16 genomic DNA using gold nanoprobes

Nanoparticles have been investigated as flagging tests for the sensitive DNA recognition that can be utilized as a part of field applications to defeat restrictions. Gold nanoparticles (AuNPs) have been widely utilized due to its optical property and capacity to get functionalized with a mixed bag of biomolecules. This study exhibits the utilization of AuNPs functionalized with single-stranded oligonucleotide (AuNP-oligo test) for fast the identification of Human Papillomavirus (HPV). This test is displayed on interdigitated electrode sensor and supported by colorimetric assay. DNA conjugated AuNP has optical property that can be controlled for the applications in diagnostics. With its identification abilities, this methodology incorporates minimal effort, strong reagents and basic identification of HPV.

Fluorescent Protein Nanowire-Mediated Protein Microarrays for Multiplexed and Highly Sensitive Pathogen Detection

Protein microarrays are powerful tools for high-throughput and simultaneous detection of different target molecules in complex biological samples. However, the sensitivity of conventional fluorescence-labeling protein detection methods is limited by the availability of signal molecules for binding to the target molecule. Here, we built a multifunctional fluorescent protein nanowire (FNw) by harnessing self-assembly of yeast amyloid protein. The FNw integrated a large number of fluorescent molecules, thereby enhancing the fluorescent signal output in target detection. The FNw was then combined with protein microarray technology to detect proteins derived from two pathogens, including influenza virus (hemagglutinin 1, HA1) and human immunodeficiency virus (p24 and gp120). The resulting detection sensitivity achieved a 100-fold improvement over a commercially available detection reagent.

Ultrasensitive fluorescence immunoassay for detection of ochratoxin A using catalase-mediated fluorescence quenching of CdTe QDs

Herein, for the first time we report an improved competitive fluorescent enzyme linked immunosorbent assay (ELISA) for the ultrasensitive detection of ochratoxin A (OTA) by using hydrogen peroxide (H2O2)-induced fluorescence quenching of mercaptopropionic acid-modified CdTe quantum dots (QDs). In this immunoassay, catalase (CAT) was labeled with OTA as a competitive antigen to connect the fluorescence signals of the QDs with the concentration of the target. Through the combinatorial use of H2O2-induced fluorescence quenching of CdTe QDs as a fluorescence signal output and the ultrahigh catalytic activity of CAT to H2O2, our proposed method could be used to perform a dynamic linear detection of OTA ranging from 0.05 pg mL(-1) to 10 pg mL(-1). The half maximal inhibitory concentration was 0.53 pg mL(-1) and the limit of detection was 0.05 pg mL(-1). These values were approximately 283- and 300-folds lower than those of horseradish peroxidase (HRP)-based conventional ELISA, respectively. The reported method is accurate, highly reproducible, and specific against other mycotoxins in agricultural products as well. In summary, the developed fluorescence immunoassay based on H2O2-induced fluorescence quenching of CdTe QDs can be used for the rapid and highly sensitive detection of mycotoxins or haptens in food safety monitoring.

Efficient synthesis of polyoxazoline-silica hybrid nanoparticles by using the “grafting-onto” approach

The first preparation of silica hybrid nanoparticles by comparing the click chemistry approach with the silane coupling of α-telechelic poly(2-methyl-2-oxazoline)s is reported.

Formation of polyoxazoline-silica nanoparticles via the surface-initiated cationic polymerization of 2-methyl-2-oxazoline

The fabrication of silica hybrid nanoparticles by a surface-initiated cationic ring-opening polymerization of poly(2-methyl-2-oxazoline)s has been described.

Determination of the ratio of fluorophore/nanoparticle for fluorescence-labelled nanoparticles

Accurate analytical methodology to determine the ratio of fluorophore molecules attached per nanoparticle; applicable to diverse fluorophore–NP conjugates.

Ru(bpy)2(phen-5-NH2)2+ doped ultrabright and photostable fluorescent silica nanoparticles

Ru(bpy)₂(phen-5-NH₂)²⁺ doped silica nanoparticles with high fluorescence brightness and controllable size are synthesized via reverse microemulsion method by introducing ethanol to reaction system.

Aggregation-induced emission enhancement and cell imaging of a novel (carbazol-N-yl)triphenylamine–BODIPY

The AIEE fluorogen BCPA–BODIPY emits strong red fluorescence and shows a good uptake by MCF-7 cells.

Nanoparticle growth and surface chemistry changes in cell-conditioned culture medium

When biomolecules attach to engineered nanoparticle (ENP) surfaces, they confer the particles with a new biological identity. Physical format may also radically alter, changing ENP stability and agglomeration state within seconds. In order to measure which biomolecules are associated with early ENP growth, we studied ENPs in conditioned medium from A549 cell culture, using dynamic light scattering (DLS) and linear trap quadrupole electron transfer dissociation mass spectrometry. Two types of 100 nm polystyrene particles (one uncoated and one with an amine functionalized surface) were used to measure the influence of surface type. In identically prepared conditioned medium, agglomeration was visible in all samples after 1 h, but was variable, indicating inter-sample variability in secretion rates and extracellular medium conditions. In samples conditioned for 1 h or more, ENP agglomeration rates varied significantly. Agglomerate size measured by DLS was well correlated with surface sequestered peptide number for uncoated but not for amine coated polystyrene ENPs. Amine-coated ENPs grew much faster and into larger agglomerates associated with fewer sequestered peptides, but including significant sequestered lactose dehydrogenase. We conclude that interference with extracellular peptide balance and oxidoreductase activity via sequestration is worthy of further study, as increased oxidative stress via this new mechanism may be important for cell toxicity.

A Label-Free Photoluminescence Genosensor Using Nanostructured Magnesium Oxide for Cholera Detection

Nanomaterial-based photoluminescence (PL) diagnostic devices offer fast and highly sensitive detection of pesticides, DNA, and toxic agents. Here we report a label-free PL genosensor for sensitive detection of Vibrio cholerae that is based on a DNA hybridization strategy utilizing nanostructured magnesium oxide (nMgO; size >30 nm) particles. The morphology and size of the synthesized nMgO were determined by transmission electron microscopic (TEM) studies. The probe DNA (pDNA) was conjugated with nMgO and characterized by X-ray photoelectron and Fourier transform infrared spectroscopic techniques. The target complementary genomic DNA (cDNA) isolated from clinical samples of V. cholerae was subjected to DNA hybridization studies using the pDNA-nMgO complex and detection of the cDNA was accomplished by measuring changes in PL intensity. The PL peak intensity measured at 700 nm (red emission) increases with the increase in cDNA concentration. A linear range of response in the developed PL genosensor was observed from 100 to 500 ng/μL with a sensitivity of 1.306 emi/ng, detection limit of 3.133 ng/μL and a regression coefficient (R(2)) of 0.987. These results show that this ultrasensitive PL genosensor has the potential for applications in the clinical diagnosis of cholera.

Multivalent linkers for improved covalent binding of oligonucleotides to dye-doped silica nanoparticles

This paper describes the fabrication of oligonucleotide-coated Cy5-doped silica nanoparticles using a combination of multivalent linkers and their use in surface-based DNA sandwich hybridization assays. Dipodal silane is introduced as a means to fabricate amine-coated silica nanoparticles and its advantages compared to monopodal silanes are discussed. The use of dipodal silane in conjunction with three different polymer linkers (oxidized dextran, linear and 8-arm polyethylene glycol (PEG)) to immobilize single-stranded DNA to Cy5-doped nanoparticles is investigated and dynamic light scattering measurements and Fourier transform infrared spectroscopy are used to follow the progression of the functionalization of the nanoparticles. We observe a significant improvement in the binding stability of the single-stranded DNA when the dipodal silane and 8-arm PEG are used in combination, when compared to alternative conjugation strategies. Both 8mer and 22mer oligonucleotides are securely conjugated to the high-brightness nanoparticles and their availability to hybridize with a complementary strand is confirmed using solution-based DNA hybridization experiments. In addition, a full surface-based sandwich assay demonstrates the potential these nanoparticles have in the detection of less than 500 femtomolar of a DNA analogue of micro RNA, miR-451.

Investigating the colloidal stability of fluorescent silica nanoparticles under isotonic conditions for biomedical applications

Fluorescent silica nanoparticle (NP) labels are of great interest in biomedical diagnostics, however, when used in bioassays under physiological conditions they rapidly agglomerate and precipitate from solution leading to high levels of non-specific binding. In this work, using size and zeta-potential data obtained from Dynamic and Electrophoretic Light Scattering analysis, the improvement in colloidal stability of silica NPs under physiological conditions was correlated with an increase in the concentration of three additives: (1) a protein, bovine serum albumin (BSA); (2) a neutral surfactant, Tween 20®; and (3) a charged surfactant, sodium dodecyl sulfate (SDS). The number of BSA molecules present in the NP corona at each concentration was calculated using UV-Vis spectroscopy and a bicinchoninic acid protein assay (BCA). The optimal concentration of each additive was also effective in stabilizing antibody labeled fluorescent nanoparticles (αNPs) under physiological conditions. Using a fourth additive, trehalose, the colloidal stability of αNPs after freeze-drying and long-term storage also significantly improved. Both as-prepared and freeze-dried αNPs were tested in a standard fluorescence immunoassay for the detection of human IgG. The as-prepared assay showed a higher sensitivity at low concentration and a lower limit of detection when compared to a free dye assay. Assays performed with freeze dried αNPs after 4 and 22 days also showed good reproducibility.

CEA-targeted nanoparticles allow specific in vivo fluorescent imaging of colorectal cancer models

Fluorescent imaging of colorectal tumor cells would improve tumor localization and allow intra-operative staging, facilitating stratification of surgical resections thereby improving patient outcomes. We aimed to develop and test fluorescent nanoparticles capable of allowing this in vivo. Dye-doped silica nanoparticles were synthesized. Anti-CEA (carcinoembryonic antigen) or control IgGs were conjugated to nanoparticles using various chemical strategies. Binding of CEA-targeted or control nanoparticles to colorectal cancer cells was quantified in vitro, and in vivo after systemic-delivery to murine xenografts. CEA-targeted, polyamidoamine dendrimer-conjugated, nanoparticles, but not control nanoparticles, allowed strong tumor-specific imaging. We are the first to demonstrate live, specific, in vivo imaging of colorectal cancer cells using antibody-targeted fluorescent nanoparticles. These nanoparticles have potential to allow intra-operative fluorescent visualization of tumor cells.

Lanthanide-doped luminescent nano-bioprobes for the detection of tumor markers

Sensitive and specific biodetection of tumor markers is essential for early-stage cancer diagnosis and therapy, and will ultimately increase the patient survival rate. As a new generation of luminescent bioprobes, lanthanide (Ln(3+))-doped inorganic luminescent nanoparticles have attracted considerable interest for a variety of biomedical applications due to their superior physicochemical properties. In this feature article, we provide a brief overview of the most recent advances in the development of Ln(3+)-doped luminescent nano-bioprobes and their promising applications for in vitro detection of tumor markers with an emphasis on the establishment of state-of-the-art assay techniques, such as heterogeneous time-resolved (TR) luminescent bioassay, dissolution-enhanced luminescent bioassay, upconversion (UC) luminescent bioassay, homogeneous TR Förster resonance energy transfer (TR-FRET) and UC-FRET bioassays. Some future prospects and efforts towards this emerging field are also envisioned.

Nanoparticle-based signal generation and amplification in microfluidic devices for bioanalysis

Signal generation and amplification based on nanomaterials and microfluidic techniques have both attracted considerable attention separately due to the demands for ultrasensitive and high-throughput detection of biomolecules. This article reviews the latest development of signal amplification strategies based on nanoparticles for bioanalysis and their integration and applications in microfluidic systems. The applications of nanoparticles in bioanalysis were categorized based on the different approaches of signal amplification, and the microfluidic techniques were summarized based on cell analysis and biomolecule detection with a focus on the integration of nanoparticle-based amplification in microfluidic devices for ultrasensitive bioanalysis. The advantages and limitations of the combination of nanoparticles-based amplification with microfluidic techniques were evaluated, and the possible developments for future research were discussed.

Photosensitive fluorescent dye contributes to phototoxicity and inflammatory responses of dye-doped silica NPs in cells and mice

Dye-doped fluorescent silica nanoparticles provide highly intense and photostable fluorescence signals. However, some dopant dye molecules are photosensitive. A widely-used photosensitive fluorescent dopant, RuBpy, was chosen to systematically investigate the phototoxicity of the dye-doped silica nanoparticles (NPs). We investigated cell viability, DNA damage, and Reactive Oxygen Species (ROS) levels in alveolar macrophages using the dye-doped NPs with or without irradiation. Our results showed that the RuBpy-doped silica NPs could induce significant amount of ROS, DNA damage, apoptosis and impaired proliferation in MH-S cells. In vivo studies in mice showed that RuBpy-doped silica NPs induced significant inflammatory cytokine production and lowered expression in signaling proteins such as ERK1/2 and NF-κB as well as increased lung injury determined by myeloperoxidase and lipid peroxidation. Strikingly, we also found that both RuBpy alone and NPs induced systemic signaling activation in the kidney compared to the liver and lung where showed highly selective signaling patterns, which is more pronounced than RuBpy-doped silica NPs. Moreover, we discovered a critical biomarker (e.g., HMGB1) for silica NPs-induced stress and toxicity and demonstrated differentially-regulated response patterns in various organs. Our results indicate for the first time that the RuBpy-doped silica NPs may impose less inflammatory responses but stronger thermotherapeutic effects on target cells in animals than naked NPs in a time- and dose-dependent manner.

Elucidation of photophysical changes and orientation of acridine orange dye on the surface of borate capped gold nanoparticles using multi-spectroscopic techniques

In the present work, we have carried out a detailed investigation on the binding interaction of acridine orange (AO) with borate capped gold nanoparticles (Au NPs) by multi spectroscopic techniques.

Silica nanoparticles for cell imaging and intracellular sensing

There is increasing interest in the use of nanoparticles (NPs) for biomedical applications. In particular, nanobiophotonic approaches using fluorescence offers the potential of high sensitivity and selectivity in applications such as cell imaging and intracellular sensing. In this review, we focus primarily on the use of fluorescent silica NPs for these applications and, in so doing, aim to enhance and complement the key recent review articles on these topics. We summarize the main synthetic approaches, namely the Stöber and microemulsion processes, and, in this context, we deal with issues in relation to both covalent and physical incorporation of different types of dyes in the particles. The important issue of NP functionalization for conjugation to biomolecules is discussed and strategies published in the recent literature are highlighted and evaluated. We cite recent examples of the use of fluorescent silica NPs for cell imaging in the areas of cancer, stem cell and infectious disease research, and we review the current literature on the use of silica NPs for intracellular sensing of oxygen, pH and ionic species. We include a short final section which seeks to identify the main challenges and obstacles in relation to the potential widespread use of these particles for in vivo diagnostics and therapeutics.

Volume labeling with Alexa Fluor dyes and surface functionalization of highly sensitive fluorescent silica (SiO2) nanoparticles

A new synthesis approach is described that allows the direct incorporation of fluorescent labels into the volume or body of SiO2 nanoparticles. In this process, fluorescent Alexa Fluor dyes with different emission wavelengths were covalently incorporated into the SiO2 nanoparticles during their formation by the hydrolysis of tetraethoxysilane. The dye molecules were homogeneously distributed throughout the SiO2 nanoparticles. The quantum yields of the Alexa Fluor volume-labeled SiO2 nanoparticles were much higher than nanoparticles labeled using conventional organic dyes. The size of the resulting nanoparticles was controlled using microemulsion reaction media with sizes in the range of 20-100 nm and a polydispersity of <15%. In comparison with conventional surface tagged particles created by post-synthesis modification, this process maintains the physical and surface chemical properties that have the most pronounced effect on colloidal stability and interactions with their surroundings. These volume-labeled nanoparticles have proven to be extremely robust, showing excellent signal strength, negligible photobleaching, and minimal loss of functional organic components. The native or "free" surface of the volume-labeled particles can be altered to achieve a specific surface functionality without altering fluorescence. Their utility was demonstrated for visualizing the association of surface-modified fluorescent particles with cultured macrophages. Differences in particle agglomeration and cell association were clearly associated with differences in observed nanoparticle toxicity. The capacity to maintain particle fluorescence while making significant changes to surface chemistry makes these particles extremely versatile and useful for studies of particle agglomeration, uptake, and transport in environmental and biological systems.

Bifunctional silica nanoparticles for the exploration of biofilms of Pseudomonas aeruginosa

Luminescent silica nanoparticles are frequently employed for biotechnology applications mainly because of their easy functionalization, photo-stability, and biocompatibility. Bifunctional silica nanoparticles (BSNPs) are described here as new efficient tools for investigating complex biological systems such as biofilms. Photoluminescence is brought about by the incorporation of a silylated ruthenium(II) complex. The surface properties of the silica particles were designed by reaction with amino-organosilanes, quaternary ammonium-organosilanes, carboxylate-organosilanes and hexamethyldisilazane. BSNPs were characterized extensively by DRIFT, (13)C and (29)Si solid state NMR, XPS, and photoluminescence. Zeta potential and contact angle measurements exhibited various surface properties (hydrophilic/hydrophobic balance and electric charge) according to the functional groups. Confocal laser scanning microscopy (CLSM) measurements showed that the spatial distribution of these nanoparticles inside a biofilm of Pseudomonas aeruginosa PAO1 depends more on their hydrophilic/hydrophobic characteristics than on their size. CLSM observations using two nanosized particles (25 and 68 nm) suggest that narrow diffusion paths exist through the extracellular polymeric substances matrix.

Fluorescent Ru(phen)3(2+)-doped silica nanoparticles-based ICTS sensor for quantitative detection of enrofloxacin residues in chicken meat

A Ru(phen)3(2+)-doped silica fluorescent nanoparticle (FN)-based immunochromatographic test strip (ICTS) sensor was developed for rapid, high sensitivity, easy to use, and low cost quantitative detection of enrofloxacin (ENR) residues in chicken meat. The fluorescence signal intensity of the FNs at the test line (FI(T)) and control line (FI(C)) was determined with a prototype of a portable fluorescent strip reader. Unique properties of Ru(phen)3(2+) doped silica nanoparticles (e.g., large Stokes shift, high emission quantum yield, and long fluorescence lifetime) were combined with the advantages of ICTS and an easy to make portable fluorescent strip reader. The signal was based on FI(T)/FI(C) ratio to effectively eliminate strip to strip variation and matrix effects. Various parameters that influenced the strip were investigated and optimized. Quantitative ENR detection with the FNs ICTS sensor using 80 μL sample took only 20 min, which is faster than the commercial ELISA kit (that took 90 min). The linear range of detection in chicken extract was established at 0.025-3.500 ng/mL with a half maximal inhibitory concentration at 0.22 ± 0.02 ng/mL. Using the optimized parameters, the limit of detection (LOD) for ENR using the FNs ICTS sensor was recorded at 0.02 ng/mL in chicken extract. This corresponds to 0.12 μg/kg chicken meat which is two (2) orders of magnitude better that the maximum residue limits (MRLs) imposed in Japan (10 μg/kg) and three (3) orders of magnitude better than those imposed in China. The intra- and inter-assay coefficient of variations (CVs) were 6.04% and 12.96% at 0.5 ng/mL, 6.92% and 12.61% at 1.0 ng/mL, and 6.66% and 11.88% at 2.0 ng/mL in chicken extract, respectively. The recoveries using the new FNs ICTS sensor from fifty (50) ENR-spiked chicken samples showed a highly significant correlation (R(2) = 0.9693) with the commercial enzyme-linked immunosorbent assay (ELISA) kit. The new FNs ICTS sensor is a simple, rapid, sensitive, accurate, and inexpensive quantitative detection of ENR residues in chicken meat and extracts.

Bacteria species identification by the statistical analysis of bacterial colonies Fresnel patterns

It was demonstrated that statistical analysis of bacteria colonies Fresnel patterns recorded in the optical system with converging spherical wave illumination is suitable for highly effective bacteria species classification. The proposed method includes Fresnel patterns recording followed by image processing and the statistical analysis based on feature extraction, feature selection, classification and classification performance methods. Examination performed on various bacteria species (Salmonella enteritidis, Staphylococcus aureus, Staphylococcus intermedius, Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa and Citrobacter freundii) revealed that the proposed method achieved very high accuracy of over 98%.