A chemically functionalized magnetic nanoplatform for rapid and specific biomolecular recognition and separation

Surface Design for Antibacterial Materials: From Fundamentals to Advanced Strategies

Healthcare-acquired infections as well as increasing antimicrobial resistance have become an urgent global challenge, thus smart alternative solutions are needed to tackle bacterial infections. Antibacterial materials in biomedical applications and hospital hygiene have attracted great interest, in particular, the emergence of surface design strategies offer an effective alternative to antibiotics, thereby preventing the possible development of bacterial resistance. In this review, recent progress on advanced surface modifications to prevent bacterial infections are addressed comprehensively, starting with the key factors against bacterial adhesion, followed by varying strategies that can inhibit biofilm formation effectively. Furthermore, "super antibacterial systems" through pre-treatment defense and targeted bactericidal system, are proposed with increasing evidence of clinical potential. Finally, the advantages and future challenges of surface strategies to resist healthcare-associated infections are discussed, with promising prospects of developing novel antimicrobial materials.

Nanobioconjugates for Signal Amplification in Electrochemical Biosensing

Nanobioconjugates are hybrid materials that result from the coalescence of biomolecules and nanomaterials. They have emerged as a strategy to amplify the signal response in the biosensor field with the potential to enhance the sensitivity and detection limits of analytical assays. This critical review collects a myriad of strategies for the development of nanobioconjugates based on the conjugation of proteins, antibodies, carbohydrates, and DNA/RNA with noble metals, quantum dots, carbon- and magnetic-based nanomaterials, polymers, and complexes. It first discusses nanobioconjugates assembly and characterization to focus on the strategies to amplify a biorecognition event in biosensing, including molecular-, enzymatic-, and electroactive complex-based approaches. It provides some examples, current challenges, and future perspectives of nanobioconjugates for the amplification of signals in electrochemical biosensing.

Solventless mechanochemical preparation of novel magnetic bioconjugates

A solventless mechanochemical approach was employed to obtain a bioconjugate (BSA-DA-Fe₂O₃) based on bovine serum albumin (BSA) and dopamine (DA) coated iron oxide magnetic nanoparticles. UV-vis measurements of the obtained material showed a distinctive peak at 280 nm which, together with the presence of N on the surface of the nanomaterial (a band at 400 eV in the XPS spectrum) and zeta potential measurements, confirmed the successful immobilization of the protein. Additionally, the presence of two bands at 1652 and 1545 cm^-1 in the FT-IR spectra of both BSA and BSA-DA-Fe₂O₃ and steady-state fluorescence analysis validated that the protein preserved its native-like structure after the mechanochemical milling process. Also the functionalized MNPs preserved their magnetic properties as have been demonstrated by their magnetic susceptibility value.

Inhibition of the lethality of Shiga-like toxin-1 by functional gold nanoparticles

Escherichia coli O157:H7 is a pathogen, which can generate Shiga-like toxins (SLTs) and cause hemolytic-uremic syndrome. Foodborne illness outbreaks caused by E. coli O157:H7 have become a global issue. Since SLTs are quite toxic, effective medicines that can reduce the damage caused by SLTs should be explored. SLTs consist of a single A and five B subunits, which can inhibit ribosome activity for protein synthesis and bind with the cell membrane of host cells, respectively. Pigeon ovalbumin (POA), i.e. a glycoprotein, is abundant in pigeon egg white (PEW) proteins. The structure of POA contains Gal-α(1→4)-Gal-β(1→4)-GlcNAc ligands, which have binding affinity toward the B subunit in SLT type-1 (SLT-1B). POA immobilized gold nanoparticles (POA-Au NPs) can be generated by reacting PEW proteins with aqueous tetrachloroauric acid in one-pot. The generated POA-Au NPs have been demonstrated to have selective trapping-capacity toward SLT-1B previously. Herein, we explore that POA-Au NPs can be used as protective agents to neutralize the toxicity of SLT-1 in SLT-1-infected model cells. The results show that the cells can be completely rescued when a sufficient amount of POA-Au NPs is used to treat the SLT-1-infected cells within 1 h.

Selective Detection of Shiga-like Toxin 1 from Complex Samples Using Pigeon Ovalbumin Functionalized Gold Nanoparticles as Affinity Probes

Escherichia coli O157:H7 is a foodborne pathogen. This bacterial strain can generate Shiga-like toxins (SLTs), which can cause serious sickness and even death. Thus, it is important to develop effective and sensitive methods that can be used to rapidly identify the presence of SLTs from complex samples. Pigeon egg white (PEW) contains abundant glycoproteins, including pigeon ovalbumin (POA) (∼60%). POA possesses Gal-α(1→4)-Gal-β(1→4)-GlcNAc termini, which can recognize the B subunits in SLT type 1 (SLT-1B). Thus, POA is a suitable probe for trapping SLT-1B. In this work, we used PEW proteins as starting materials to react with aqueous tetrachloroauric acid for generation of PEW-protein-immobilized gold nanoparticles (AuNPs@PEW) via one-pot reactions. We demonstrated that the generated AuNPs@PEW were mainly dominated by POA-immobilized Au NPs. The as-prepared AuNPs@PEW were used as affinity probes to selectively probe SLT-1B from complex cell lysates derived from E. coli O157:H7. The selective trapping step can be completed within ∼90 s under microwave heating (power = 450 W) to enrich sufficient SLT-1B for matrix-assisted laser desorption/ionization (MALDI) mass spectrometric analysis. Furthermore, this approach can be used to detect SLT-1B at a concentration as low as ∼40 pM. The feasibility of using the proposed method to selectively detect SLT-1B from ham contaminated by E. coli O157:H7 was also demonstrated.

Light-controlled active release of photocaged ciprofloxacin for lipopolysaccharide-targeted drug delivery using dendrimer conjugates

We report an active delivery mechanism targeted specifically to Gram(-) bacteria based on the photochemical release of photocaged ciprofloxacin carried by a cell wall-targeted dendrimer nanoconjugate.

Novel Functionalized Polythiophene-Coated Fe₃O₄ Nanoparticles for Magnetic Solid-Phase Extraction of Phthalates

Poly(phenyl-(4-(6-thiophen-3-yl-hexyloxy)-benzylidene)-amine) (P3TArH) was successfully synthesized and coated on the surface of Fe₃O₄ magnetic nanoparticles (MNPs). The nanocomposites were characterized by Fourier transform infra-red (FTIR), X-ray diffractometry (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, analyzer transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM). P3TArH-coated MNPs (MNP@P3TArH) showed higher capabilities for the extraction of commonly-used phthalates and were optimized for the magnetic-solid phase extraction (MSPE) of environmental samples. Separation and determination of the extracted phthalates, namely dimethyl phthalate (DMP), diethyl phthalate (DEP), dipropyl phthalate (DPP), dibutyl phthalate (DBP), butyl benzyl phthalate (BBP), dicyclohexyl phthalate (DCP), di-ethylhexyl phthalate (DEHP) and di-n-octyl phthalate (DNOP), were conducted by a gas chromatography-flame ionization detector (GC-FID). The best working conditions were as follows; sample at pH 7, 30 min extraction time, ethyl acetate as the elution solvent, 500-µL elution solvent volumes, 10 min desorption time, 10-mg adsorbent dosage, 20-mL sample loading volume and 15 g·L-1 concentration of NaCl. Under the optimized conditions, the analytical performances were determined with a linear range of 0.1⁻50 µg·L-1 and a limit of detection at 0.08⁻0.468 µg·L-1 for all of the analytes studied. The intra-day (n = 7) and inter-day (n = 3) relative standard deviations (RSD%) of three replicates were each demonstrated in the range of 3.7⁻4.9 and 3.0⁻5.0, respectively. The steadiness and reusability studies suggested that the MNP@P3TArH could be used up to five cycles. The proposed method was executed for the analysis of real water samples, namely commercial bottled mineral water and bottled fresh milk, whereby recoveries in the range of 68%⁻101% and RSD% lower than 7.7 were attained.

Polymer functionalized magnetic nanoconstructs for immunomagnetic separation of analytes

Core–shell polymer functionalized magnetic nanoparticles are promising material for rapid immunomagnetic separation and detection of analyte.

Highly stable water-soluble magnetic nanoparticles synthesized through combined co-precipitation, surface-modification, and decomposition of a hybrid hydrogel

The synthesized magnetic nanoparticles were stable not only in aqueous media but also in mixtures of water and hydrophilic organic solvents.

Magnetic Nanoparticle-Based Platform for Characterization of Shiga-like Toxin 1 from Complex Samples

Foodborne illness outbreaks resulting from contamination of Escherichia coli O157:H7 remain a serious concern in food safety. E. coli O157:H7 can cause bloody diarrhea, hemolytic uremic syndrome, or even death. The pathogenicity of E. coli O157:H7 is mainly caused by the expression of Shiga-like toxins (SLTs), i.e., SLT-1 and SLT-2. SLTs are pentamers composed of a single A and five B subunits. In this study, we propose a magnetic nanoparticle (MNP)-based platform to rapidly identify SLT-1 from the complex cell lysate of E. coli O157:H7. The core of the MNPs is made of iron oxide, whereas the surface of the core is coated with a thin layer of alumina (Fe3O4@Al2O3 MNPs). The Fe3O4@Al2O3 MNPs are functionalized with pigeon ovalbumin (POA), which contains Gal-α(1→4)-Gal-β(1→4)-GlcNAc termini that can bind SLT-1B selectively. Furthermore, POA is a phosphate protein. Thus, it can be easily immobilized on the surface of the Fe3O4@Al2O3 MNPs through aluminum phosphate chelation under microwave heating within 1.5 min. The generated POA-Fe3O4@Al2O3 MNPs are capable of effectively enriching SLT-1B from complex cell lysates simply by pipetting 20 μL of the sample in and out of the tip in a vial for ∼1 min. To release SLT-1 from the MNPs, Gal-α(1→4)-Gal disaccharides were used for displacement. The released target species are sufficient to be identified by matrix-assisted laser desorption/ionization mass spectrometry. Although the sample volume used in this approach is small (20 μL) and the enrichment time is short (1 min), the selectivity of this approach toward SLT-1B is quite good. We have demonstrated the effectiveness of this approach for rapid determination of the presence of SLT-1 from complex cell lysates and ham/juice samples based on the detection of SLT-1B.

Recent advances in biosensing using magnetic glyconanoparticles

In this critical review we discuss the most recent advances in the field of biosensing applications of magnetic glyconanoparticles. We first give an overview of the main synthetic routes to obtain magnetic-nanoparticle-carbohydrate conjugates and then we highlight their most promising applications for magnetic relaxation switching sensing, cell and pathogen detection, cell targeting and magnetic resonance imaging. We end with a critical perspective of the field, identifying the main challenges to be overcome, but also the areas where the most promising developments are likely to happen in the coming decades.

A lipopolysaccharide binding heteromultivalent dendrimer nanoplatform for Gram negative cell targeting

Heteromultivalent design of PAMAM dendrimer by conjugation with polymyxin B (PMB) ligand and excess auxiliary ethanolamine (EA) branches led to lipopolysaccharide (LPS) avidity two orders of magnitude greater than free PMB.

Recent advances in bacteria identification by matrix-assisted laser desorption/ionization mass spectrometry using nanomaterials as affinity probes

Identifying trace amounts of bacteria rapidly, accurately, selectively, and with high sensitivity is important to ensuring the safety of food and diagnosing infectious bacterial diseases. Microbial diseases constitute the major cause of death in many developing and developed countries of the world. The early detection of pathogenic bacteria is crucial in preventing, treating, and containing the spread of infections, and there is an urgent requirement for sensitive, specific, and accurate diagnostic tests. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is an extremely selective and sensitive analytical tool that can be used to characterize different species of pathogenic bacteria. Various functionalized or unmodified nanomaterials can be used as affinity probes to capture and concentrate microorganisms. Recent developments in bacterial detection using nanomaterials-assisted MALDI-MS approaches are highlighted in this article. A comprehensive table listing MALDI-MS approaches for identifying pathogenic bacteria, categorized by the nanomaterials used, is provided.

Multivalent glycosylated nanoparticles for studying carbohydrate–protein interactions

Glyconanoparticles decorated with multiple copies of various biologically relevant carbohydrates serve as scaffolds for protein binding assay, molecular imaging, targeted therapy, and bacterium detection.

Application of functionalized magnetic nanoparticles in sample preparation

Functionalized magnetic nanoparticles have attracted much attention in sample preparation because of their excellent performance compared with traditional sample-preparation sorbents. In this review, we describe the application of magnetic nanoparticles functionalized with silica, octadecylsilane, carbon-based material, surfactants, and polymers as adsorbents for separation and preconcentration of analytes from a variety of matrices. Magnetic solid-phase extraction (MSPE) techniques, mainly reported in the last five years, are presented and discussed.

BAD-lectins: boronic acid-decorated lectins with enhanced binding affinity for the selective enrichment of glycoproteins

The weak and variable binding affinities exhibited by lectin-carbohydrate interactions have often compromised the practical utility of lectin in capturing glycoproteins for glycoproteomic applications. We report here the development and applications of a new type of hybrid biomaterial, namely a boronic acid-decorated lectin (BAD-lectin), for efficient bifunctional glycoprotein labeling and enrichment. Our binding studies showed an enhanced affinity by BAD-lectin, likely to be mediated via the formation of boronate ester linkages between the lectin and glycan subsequent to the initial recognition process and thus preserving its glycan-specificity. Moreover, when attached to magnetic nanoparticles (BAD-lectin@MNPs), 2 to 60-fold improvement on detection sensitivity and enrichment efficiency for specific glycoproteins was observed over the independent use of either lectin or BA. Tested at the level of whole cell lysates for glycoproteomic applications, three different types of BAD-lectin@MNPs exhibited excellent specificities with only 6% overlapping among the 295 N-linked glycopeptides identified. As many as 236 N-linked glycopeptides (80%) were uniquely identified by one of the BAD-lectin@MNPs. These results indicated that the enhanced glycan-selective recognition and binding affinity of BAD-lectin@MNPs will facilitate a complementary identification of the under-explored glycoproteome.