One-step and high-density protein immobilization on epoxysilane-modified silica nanoparticles

Poly-L-lysine functionalized silica membrane-enhanced colorimetric loop-mediated isothermal amplification for sensitive and rapid detection of Vibrio parahaemolyticus

Traditional detection of foodborne pathogen relies on advanced analyzers, which is inadequate for the rapid control of infections, particularly in resource-limited regions, highlighting the necessity of developing detection systems for point-of-care testing (POCT). Herein, taking Vibrio parahaemolyticus as a detecting target, we reported poly-L-lysine functionalized silica membrane (PL-SM) based loop-mediated isothermal amplification (pLAMP) platform for sensitive on-site detection. This platform utilized PL-SM for DNA capture driven by the electrostatic attraction between protonated amine groups of poly-L-lysine and negatively charged phosphate groups of DNA, followed by introducing a colorimetric indicator calcein for LAMP amplification. After optimization, the colorimetric mode of pLAMP allowed the screening of V. parahaemolyticus with the visual limit of detection (vLOD) of 1 CFU/mL in 50 min, 1000-fold lower than methods based on commercial kits. Validation was performed using 174 seafoods, which was 97 % concordant to those of real-time PCR. Furthermore, an image processing approach was developed based on the analysis of the RGB under UV light. Paired with a smartphone, the objective analytical method could be readily conducted in the field. Thus, we propose a sensitive and visual detection platform, which may play a crucial role in improving testing efficiency and accuracy in food safety, medical diagnostics, and environmental monitoring.

Immobilizing calcium-dependent affinity ligand onto iron oxide nanoparticles for mild magnetic mAb separation

Current downstream processing of monoclonal antibodies (mAbs) is limited in throughput and requires harsh pH conditions for mAb elution from Protein A affinity ligands. The use of an engineered calcium-dependent ligand (ZCa) in magnetic separation applications promises improvements due to mild elution conditions, fast processability, and process integration prospects. In this work, we synthesized and evaluated three magnetic nanoparticle types immobilized with the cysteine-tagged ligand ZCa-cys. Ligand homodimers were physically immobilized onto bare iron oxide nanoparticles (MNP) and MNP coated with tetraethyl orthosilicate (MNP@TEOS). In contrast, ZCa-cys was covalently and more site-directedly immobilized onto MNP coated with (3-glycidyloxypropyl)trimethoxysilane (MNP@GPTMS) via a preferential cysteine-mediated epoxy ring opening reaction. Both coated MNP showed suitable characteristics, with MNP@TEOS@ZCa-cys demonstrating larger immunoglobulin G (IgG) capacity (196 mg g -1) and the GPTMS-coated particles showing faster magnetic attraction and higher IgG recovery (88 %). The particles pave the way for the development of calcium-dependent magnetic separation processes.

Preparation of the immobilized α1A-adrenoceptor column by the ultra-high affinity protein pair CL7/Im7 and its application in drug-protein interaction analysis

Immobilizing the target protein on a solid surface with controlled orientation, high specificity, and maintained activity is a proven strategy to enhance the stability of the protein. In this study, we employed an ultra-high affinity protein pair consisting of a mutant of colicin E7 Dnase and its corresponding inhibitor, immunity protein 7(Im7), to develop an immobilized α1A-adrenoceptor (α1A-AR) column. Briefly, we expressed α1A-AR fused with CL7 as a tag at its C-terminus in Escherichia coli cells. Meanwhile, we got His-tagged Im7 at the same manner. Following purification, the His-tagged Im7 was utilized to functionalize the macro-porous silica gel. Leveraging the ultra-high affinity between the protein pair, we achieved robust and specific covalent immobilization of α1A-AR covalently at ambient conditions in buffer solutions, without the requirement for additional regents. The successful immobilization of the receptor, without extraneous protein adsorption, was confirmed through X ray photoelectron spectroscopy and chromatographic investigations. Frontal analysis and adsorption energy distribution analysis further validated the feasibility of the immobilization method. Our findings align well with those reported in the literature. This work is poised to provide a modular platform for conducting effective investigations into the binding interactions between other functional proteins and the drugs.

Metal Oxide Nanostructures Enhanced Microfluidic Platform for Efficient and Sensitive Immunofluorescence Detection of Dengue Virus

Rapid and sensitive detection of Dengue virus remains a critical challenge in global public health. This study presents the development and evaluation of a Zinc Oxide nanorod (ZnO NR)-surface-integrated microfluidic platform for the early detection of Dengue virus. Utilizing a seed-assisted hydrothermal synthesis method, high-purity ZnO NRs were synthesized, characterized by their hexagonal wurtzite structure and a high surface-to-volume ratio, offering abundant binding sites for bioconjugation. Further, a comparative analysis demonstrated that the ZnO NR substrate outperformed traditional bare glass substrates in functionalization efficiency with 4G2 monoclonal antibody (mAb). Subsequent optimization of the functionalization process identified 4% (3-Glycidyloxypropyl)trimethoxysilane (GPTMS) as the most effective surface modifier. The integration of this substrate within a herringbone-structured microfluidic platform resulted in a robust device for immunofluorescence detection of DENV-3. The limit of detection (LOD) for DENV-3 was observed to be as low as 3.1 × 10-4 ng/mL, highlighting the remarkable sensitivity of the ZnO NR-integrated microfluidic device. This study emphasizes the potential of ZnO NRs and the developed microfluidic platform for the early detection of DENV-3, with possible expansion to other biological targets, hence paving the way for enhanced public health responses and improved disease management strategies.

Magnetic Nanoplatforms for Covalent Protein Immobilization Based on Spy Chemistry

Immobilization of proteins on magnetic nanoparticles (MNPs) is an effective approach to improve protein stability and facilitate separation of immobilized proteins for repeated use. Herein, we exploited the efficient SpyTag-SpyCatcher chemistry for conjugation of functional proteins onto MNPs and established a robust magnetic-responsive nanoparticle platform for protein immobilization. To maximize the loading capacity and achieve outstanding water dispersity, the SpyTag peptide was incorporated into the surface-charged polymers of MNPs, which provided abundant active sites for Spy chemistry while maintaining excellent colloidal stability in buffer solution. Conjugation between enhanced green fluorescence protein (EGFP)-SpyCatcher-fused proteins and SpyTag-functionalized MNPs was efficient at ambient conditions without adding enzymes or chemical cross-linkers. Benefiting from the excellent water dispersity and interface compatibility, the surface Spy reaction has fast kinetics, which is comparable to that of the solution Spy reaction. No activity loss was observed on EGFP after conjugation due to the site-selective nature of Spy chemistry. The immobilization process of EGFP on MNPs was highly specific and robust, which was not affected by the presence of other proteins and detergents, such as bovine serum albumin and Tween 20. The MNP platform was demonstrated to be protective to the conjugated EGFP and significantly improved the shelf life of immobilized proteins. In addition, experiments confirmed the retained magnetophoresis of the MNP after protein loading, demonstrating fast MNP recovery under an external magnetic field. This MNP is expected to provide a versatile and modular platform to achieve effective and specific immobilization of other functional proteins, enabling easy reuse and storage.

Improving the Protective Properties of Shellac-Based Varnishes by Functionalized Nanoparticles

Shellac is a natural varnish still known as one of the most elegant finishes for furniture and musical instruments, and currently used for restoration and refinishing of wooden antiques. However, it displays some limitations such as (i) sensitivity to alcoholic solvents (ii) softness of the coating, and (iii) considerable weathering due to photo- and bio-degradation. Hence, the main aim of this study was to improve the properties of shellac-based finish by introducing functionalized nanoparticles. Two inorganic nano-sized materials were considered: ZnO that was expected to reduce photo- and bio-degradation problems, and ZrO2 that was expected to improve the hardness of the varnish. Nanoparticles were synthesized and treated with a bifunctional silane coupling agent. Both plain and functionalized nanoparticles were extensively characterized using different experimental techniques. Functionalized nanoparticles were grafted on shellac through a reaction involving the epoxy-rings introduced on their surface. The resulting modified varnishes were applied on maple wood specimens according to traditional procedures. Different instrumental techniques and testing methods were used to characterize both nano-sized materials and the corresponding nanocomposites, as well as to evaluate the performance of the new coatings. The investigated composite materials display the same aesthetic appearance as plain shellac, while some other properties were improved. In particular, both nanocomposites are distinctly less soluble in alcohols than plain shellac and display antifungal properties. Moreover, coating containing functionalized ZnO nanoparticles displays photo-protection behavior, while shellac modified with ZrO2 nanoparticles exhibits a higher hardness when compared to the traditional varnish.

Dye-doped silica nanoparticles: synthesis, surface chemistry and bioapplications

Background

Fluorescent silica nanoparticles have been extensively utilised in a broad range of biological applications and are facilitated by their predictable, well-understood, flexible chemistry and apparent biocompatibility. The ability to couple various siloxane precursors with fluorescent dyes and to be subsequently incorporated into silica nanoparticles has made it possible to engineer these fluorophores-doped nanomaterials to specific optical requirements in biological experimentation. Consequently, this class of nanomaterial has been used in applications across immunodiagnostics, drug delivery and human-trial bioimaging in cancer research.

Main body

This review summarises the state-of-the-art of the use of dye-doped silica nanoparticles in bioapplications and firstly accounts for the common nanoparticle synthesis methods, surface modification approaches and different bioconjugation strategies employed to generate biomolecule-coated nanoparticles. The use of dye-doped silica nanoparticles in immunoassays/biosensing, bioimaging and drug delivery is then provided and possible future directions in the field are highlighted. Other non-cancer-related applications involving silica nanoparticles are also briefly discussed. Importantly, the impact of how the protein corona has changed our understanding of NP interactions with biological systems is described, as well as demonstrations of its capacity to be favourably manipulated.

Conclusions

Dye-doped silica nanoparticles have found success in the immunodiagnostics domain and have also shown promise as bioimaging agents in human clinical trials. Their use in cancer delivery has been restricted to murine models, as has been the case for the vast majority of nanomaterials intended for cancer therapy. This is hampered by the need for more human-like disease models and the lack of standardisation towards assessing nanoparticle toxicity. However, developments in the manipulation of the protein corona have improved the understanding of fundamental bio–nano interactions, and will undoubtedly assist in the translation of silica nanoparticles for disease treatment to the clinic.

Lipase mediated synthesis of polycaprolactone and its silica nanohybrid

In this study, rice husk ash (RHA) silanized with 3-glycidyloxypropyl trimethoxysilane was used as support material to immobilize Candida antarctica lipase B. The developed biocatalyst was then utilized in the ring opening polymerization (ROP) of ε-caprolactone and in situ development of PCL/Silica nanohybrid. The silanization degree of RHA was determined as 4 % (w) by thermal gravimetric analysis (TGA). Structural investigations and calculation of molecular weights of nanohybrids were realized by proton nuclear magnetic resonance (1H NMR). Crystallinity was determined by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Scanning Electron Microscopy (SEM) was used for morphological observations. Accordingly, the PCL composition in the nanohybrid was determined as 4 %, approximately. Short chained amorphous PCL was synthesized with a number average molecular weight of 4400 g/mol and crystallinity degree of 23 %. In regards to these properties, synthesized PCL/RHA composite can find use biomedical applications.

GPTMS-Modified Bredigite/PHBV Nanofibrous Bone Scaffolds with Enhanced Mechanical and Biological Properties

Bioceramic nanoparticles with high specific surface area often tend to agglomerate in the polymer matrix, which results in undesirable mechanical properties of the composites and poor cell spreading and attachment. In the present work, bredigite (BR) nanoparticles were modified with an organosilane coupling agent, 3-glycidoxypropyltrimethoxysilane (GPTMS), to enhance its dispersibility in the polymer matrix. The polyhydroxybutyrate-co-hydroxyvaletare (PHBV) nanofibrous scaffolds containing either bredigite or GPTMS-modified bredigite (G-BR) nanoparticles were fabricated using electrospinning technique and characterized using scanning electron microscopy, transmission electron microscopy, and tensile strength. Results demonstrated that modification of bredigite was effective in enhancing nanoparticle dispersion in the PHBV matrix. PHBV/G-BR scaffold showed improved mechanical properties compared to PHBV and PHBV/BR, especially at the higher concentration of nanoparticles. In vitro bioactivity assay performed in the simulated body fluid (SBF) indicated that composite PHBV scaffolds were able to induce the formation of apatite deposits after incubation in SBF. From the results of in vitro biological assay, it is concluded that the synergetic effect of BR and GPTMS provided an enhanced hFob cells attachment and proliferation. The developed PHBV/G-BR nanofibrous scaffolds may be considered for application in bone tissue engineering.

Highly Flexible Platform for Tuning Surface Properties of Silica Nanoparticles and Monitoring Their Biological Interaction

The following work presents a simple, reliable and scalable seeding-growth methodology to prepare silica nanoparticles (SiO2 NPs) (20, 30, 50 and 80 nm) directly in aqueous phase, both as plain- as well as fluorescent-labeled silica. The amount of fluorescent label per particle remained constant regardless of size, which facilitates measurements in terms of number-based concentrations. SiO2 NPs in dispersion were functionalized with an epoxysilane, thus providing a flexible platform for the covalent linkage of wide variety of molecules under mild experimental conditions. This approach was validated with ethylenediamine, two different amino acids and three akylamines to generate a variety of surface modifications. Accurate characterization of particle size, size distributions, morphology and surface chemistry is provided, both for as-synthesized particles and after incubation in cell culture medium. The impact of physicochemical properties of SiO2 NPs was investigated with human alveolar basal epithelial cells (A549) such as the effect in cytotoxicity, cell internalization and membrane interaction.

Designing the nanoparticle-biomolecule interface for "targeting and therapeutic delivery"

The endogenous transport mechanisms which occur in living organisms have evolved to allow selective transport and processing operate on a scale of tens of nanometers. This presents the possibility of unprecedented access for engineered nanoscale materials to organs and sub-cellular locations, materials which may in principle be targeted to precise locations for diagnostic or therapeutic gain. For this reason, nano-architectures could represent a truly radical departure as delivery agents for drugs, genes and therapies to treat a host of diseases. Thus, for active targeting, unlike the case of small molecular drugs where molecular structure has evolved to promote higher physiochemical affinity to specific sites, one aims to exploit these energy dependant endogenous processes. Many active targeting strategies have been developed, but despite this truly remarkable potential, in applications they have met with mixed success to date. This situation may have more to do with our current understanding and integration of knowledge across disciplines, than any intrinsic limitation on the vision itself. In this review article we suggest that much more fundamental and detailed control of the nanoparticle-biomolecule interface is required for sustained and general success in this field. In the simplest manifestation, pristine nanoparticles in biological fluids act as a scaffold for biomolecules, which adsorb rapidly to the nanoparticles' surface, conferring a new biological identity to the nanoparticles. It is this nanoparticle-biomolecule interface that is 'read' and acted upon by the cellular machinery. Moreover, where targeting moieties are grafted onto nanoparticles, they may not retain their function as a result of poor orientation, and structural or conformational disruption. Further surface adsorption of biomolecules from the surrounding environment i.e. the formation of a biomolecule corona may also obscure specific surface recognition. To transfer the remarkable possibilities of nanoscale interactions in biology into therapeutics one may need a more focused and dedicated approach to the understanding of the in situ (in vivo) interface between engineered nanomaedicines and their targets.