Biomimetic Silica Research Articles

Synthesis of gold-spikes decorated biomimetic silica microrod for photothermal agents

Photo-absorbing molecules or nanoparticles as microscopic heat sources are expected to improve the therapeutic accuracy and reduce side effect on normal tissues. Herein, gold (Au)-spikes decorated silica structure based on a unicellular organism (Escherichia coli) as a framework was synthesized using E@SiO2-Au spikes as the reusable photothermal agents. The synthesized E@SiO2-Au spikes were stable under the irradiation of 808nm NIR laser after 5 times recycling experiments, with no temperature decrease tendencies. As a result of temperature evaluation measurements, E@SiO2-Au spikes showed better performance with higher conversion efficiency and more stable activity during multiple reaction runs.

Superhydrophilic Conversion of Stainless Steel Surfaces by Biomimetic Silica Coating and Its Effect on Marine Fouling

Superhydrophilic Conversion of Stainless Steel Surfaces by Biomimetic Silica Coating and Its Effect on Marine Fouling

Biomimetic Silica Nanocapsules for Tunable Sustained Release and Cargo Protection.

Silica nanocapsules have attracted tremendous interest for encapsulation, protection, and controlled release of various cargoes due to their unique hierarchical core-shell structure. However, it remains challenging to synthesize silica nanocapsules having high cargo-loading capacity and cargo-protection capability without compromising process simplicity and biocompatibility properties. Here, we synthesized oil-core silica-shell nanocapsules under environmentally friendly conditions by a novel emulsion and biomimetic dual-templating approach using a dual-functional protein, in lieu of petrochemical surfactants, thus avoiding the necessities for the removal of toxic components. A light- and pH-sensitive compound can be facilely encapsulated in the silica nanocapsules with the encapsulation efficiency of nearly 100%. Release of the encapsulated active from the nanocapsules was not shown an indication of undesired burst release. Instead, the release can be tuned by controlling the silica-shell thicknesses (i.e., 40 and 77 nm from which the cargo released at 42.0 and 31.3% of the initial amount after 32 days, respectively). The release kinetics were fitted well to the Higuchi model, enabling the possibility of the prediction of release kinetics as a function of shell thickness, thus achieving design-for-purpose silica nanocapsules. Furthermore, the nanocapsules showed excellent alkaline- and sunlight-shielding protective efficacies, which resulted in significantly prolonged half-life of the sensitive cargo. Our biomimetic silica nanocapsules provide a nanocarrier platform for applications that demand process scalability, sustainability, and biocompatibility coupled with unique cargo-protection and controlled-release properties.

Hierarchically Branched Nanostructures in Biomimetic Silica Films, Controlled by Counteranion-Exchange

Hierarchically Branched Nanostructures in Biomimetic Silica Films, Controlled by Counteranion-Exchange

Novel Plasma Based Microfluidic Assay for Measuring Fibrin Formation,Thrombin Generation and Fibrinolysis Under Flow: Monitoring Patients with Hemophilia on Inhibitors

INTRODUCTIONThe unpredictable clinical response of patients to bypassing therapy and the lack of a proper laboratory tools to measure clot formation and stability renders prophylaxis and surgery on these patients a huge challenge. These patients are at a risk for bleeding or thromboembolic complications.AIMSIn this study we introduce a novel plasma based microfluidic assay that can qualitatively and quantitatively measure fibrin deposition, thrombin and plasmin generation, and fibrinolysis under flow.We then examined the dynamics of thrombus formation in patients with hemophilia and their response to replacement and bypass therapies under flow conditions.METHODSCoagulation in the plasma based assay was initiated by spherical 1µm lipidated- Tissue Factor biomimetic silica beads which were patterned into 200µm circles on a substrate surface. Plasma samples were obtained from Hemophilia patients and inhibitor patients, before and after replacement or bypassing treatment and perfused over the tissue factor rich surfaces at a sheer rate of 100 s-1 Fibrinolysis was initiated with the addition of tPAto the plasma samples before perfusion.RESULTSThe microfluidic assay was sensitive enough to measure the activation of coagulation triggered by the bypassing agents. Fibrin generation and thrombin generation were measurable both qualitatively and quantitatively using three metrics; lag time, rate of production and maximum quantity produced. Individuals on replacement therapy showed normalized fibrin formation with a 69% increase in fibrin formation, a decrease in lag time and an overall increase in maximum fibrin and thrombin production (See attached Figure).The microfluidic assay was also able to show an increase in overall fibrin generation in certain Individuals that were given more bypassing treatment than needed. Compared to healthy controls the rate of fibrin generation and maximum fibrin was greater, thereby identifying a risk for prothrombotic state. (See attached Figure). Finally, using the microfluidic assay we were able to observe both clot formation and lysis and asses the the stability of the fibrin clot produced when these inhibitor patients were on and off treatments, which reflects a more complete picture of the coagulation process.CONCLUSIONWe are able to show that individuals, treated by replacement therapies showed normalized clot formation. Individuals with hemophilia treated by bypassing therapies also showed normalized clot formation. Sometimes however, the fibrin production is more than a normal control, which could lead to a risk of prothrombosis. By using microfluidic assay, the treatment can be given in doses and fibrin production observed, to decrease the overall fibrin formation from a hypocoagulable to a hemostatic state, avoiding hypercoagulability. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Encapsulated Laccases for the Room-Temperature Oxidation of Aromatics: Towards Synthetic Low-Molecular-Weight Lignins.

A new approach for the encapsulation of laccases with enhanced activity and stability by biomimetic silica mineralisation is reported. A range of lignin model compounds, which includes syringol, syringyl acid, 4-vinylphenol, gallic acid, vanillic acid and guaiacol, was oxidised to lignin-type polymers by the silica-immobilised laccase systems at room temperature. The oxidation rate of the immobilised systems was lower than that of the free enzyme counterparts, but interesting products were observed with the new bio-catalytic materials, which showed reusability and good stability.

Recent developments and applications of bioinspired silicification

Bioinspired synthesis of silica has attracted attention from a wide range of researchers as novel route for fabrication of various nanomaterials. Proteins including silaffins and silicateins as well as polyamines from marine diatoms and sponges are key biomolecules in these biomimetic silicification processes. These methods allow silica mineralization from various silica precursors under mild, biologically compatible conditions in an unprecedentedly fast and facile manner. Notably, the silica polycondensation entails the concomitant encapsulation of other molecules in the reaction solutions. Due to the efficient encapsulation and synergetic effects brought by the encapsulated molecules and the characteristics of biomimetic silica synthesis as well as the mechanical and chemical properties of silica itself, the silica- biomolecule nanocomposites have broad applications in biocatalysis, biosensor, and biomedical areas. Introduction and combination of novel template, precursors, inorganics, or enzymes with the previously used strategies will allow construction of more efficient, purpose-optimized silica nanomaterials with controlled size, composition, and morphology.

Insights into the Role of Biomineralizing Peptide Surfactants on Making Nanoemulsion-Templated Silica Nanocapsules.

We recently developed a novel approach for making oil-core silica-shell nanocapsules using designed bifunctional peptides (also called biomineralizing peptide surfactants) having both surface activity and biomineralization activity. Using the bifunctional peptides, oil-in-water nanoemulsion templates can be readily prepared, followed by the silicification directed exclusively onto the oil droplet surfaces and thus the formation of the silica shell. To explore their roles in the synthesis of silica nanocapsules, two bifunctional peptides, AM1 and SurSi, were systematically studied and compared. Peptide AM1, which was designed as a stimuli-responsive surfactant, demonstrated quick adsorption kinetics with a rapid decrease in the oil-water interfacial tension, thus resulting in the formation of nanoemulsions with a droplet size as small as 38 nm. Additionally, the nanoemulsions showed good stability over 4 weeks because of the formation of a histidine-Zn(2+) interfacial network. In comparison, the SurSi peptide that was designed by modularizing an AM1-like surface-active module with a highly cationic biosilicification-active module was unable to effectively reduce the oil-water interfacial tension because of its high molecular charge at neutral pH. The slow adsorption resulted in the formation of less stable nanoemulsions with a larger size (60 nm) than that of AM1. Besides, both AM1 and SurSi were found to be able to induce biomimetic silica formation. SurSi produced well-dispersed and uniform silica nanospheres in the bulk solution, whereas AM1 generated only irregular silica aggregates. Consequently, well-defined silica nanocapsules were synthesized using SurSi nanoemulsion templates, whereas silica aggregates instead of nanocapsules predominated when templating AM1 nanoemulsions. This finding indicated that the capability of peptide surfactants to form isolated silica nanospheres might play a role in the successful fabrication of silica nanocapsules. This fundamental study provides insights into the design of bifunctional peptides for making silica nanocapsules.

Janus Silica Hollow Spheres Prepared via Interfacial Biosilicification.

A poly(ethylene glycol)-b-poly(L-lysine)-b-poly(styrene) (PEG-PLL-PS) triblock copolymer, which contains a cationic PLL block as the middle block, is synthesized via a combination of ring-opening polymerization (ROP) and atom-transfer radical polymerization (ATRP). The PEG-PLL-PS (ELS) triblock is employed as a macromolecular surfactant to form a stable oil-in-water (O/W) emulsion, which is subsequently used as the template to prepare Janus silica hollow spheres (JHS) via a one-pot biosilicification reaction. For the emulsion template, the middle PLL block assembles at the O/W interface and directs the biomimetic silica synthesis in the presence of phosphate buffer and silicic acid precursors. This biosilicification process takes place only in the intermediate layer between water and the organic interior phase, leading to the formation of silica JHSs with hydrophobic PS chains tethered to the inner surface and PEG attached to the outer surface. The three-layer JHSs, namely, PEG/silica-polylysine/PS composites, were verified by electron microscopy. Upon further breaking these JHSs into species, polymer-grafted Janus silica nanoplates (JPLs) can be obtained. Our studies provide an efficient one-step method for preparing hybrid silica Janus structures within minutes.

Biomimetic Growth of Ultrathin Silica Sheets Using Artificial Amphiphilic Peptides

Biomimetic silica sheets synthesized by synthetic leucine–lysine peptides with different foldings from tetramethyl orthosilicate are presented. The nanometer-thin and micrometer-size silica sheets are stable and self-supported. Moreover, the morphology of the sheets is controlled by the secondary structure of the peptides when interacting with the silica. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Mesoporous CLEAs-silica composite microparticles with high activity and enhanced stability.

A novel enzyme immobilization approach was used to generate mesoporous enzymes-silica composite microparticles by co-entrapping gelatinized starch and cross-linked phenylalanine ammonia lyase (PAL) aggregates (CLEAs) containing gelatinized starch into biomemitic silica and subsequently removing the starch by α-amylase treatment. During the preparation process, the gelatinzed starch served as a pore-forming agent to create pores in CLEAs and biomimetic silica. The resulting mesoporous CLEAs-silica composite microparticles exhibited higher activity and stability than native PAL, conventional CLEAs, and PAL encapsulated in biomimetic silica. Furthermore, the mesoporous CLEAs-silica composite microparticles displayed good reusability due to its suitable size and mechanical properties, and had excellent stability for storage. The superior catalytic performances were attributed to the combinational unique structure from the intra-cross-linking among enzyme aggregates and hard mesoporous silica shell, which not only decreased the enzyme-support negative interaction and mass-transfer limitations, but also improved the mechanical properties and monodispersity. This approach will be highly beneficial for preparing various bioactive mesoporous composites with excellent catalytic performance.

Magnetic mesoporous enzyme–silica composites with high activity and enhanced stability

AbstractBACKGROUNDEncapsulation of enzymes in biomimetic silica seems to be a promising immobilization method due to mild processing conditions and short preparation time. However, biomimetic silica particles may be considered too small for industrial applications because they result in difficult recovery. Furthermore, the use of R5 peptide or polymers as catalyst usually causes protein denaturation. To overcome these drawbacks, a new stable and recyclable biocatalyst based on co‐encapsulation of magnetic nanoparticles and phenylalanine ammonia lyase (PAL) in biomimetic silica has been prepared using enzyme‐assisted direct condensation reactions of silicon oxide with tetramethoxysilane (TMOS).RESULTSUnder optimal conditions (10 mg mL−1 nanoparticles, 4.5 U mL−1 PAL, 0.8 mol L−1 TMOS), the highest activity recovery (52%) of encapsulated PAL was obtained. Compared with conventional PAL encapsulated in biomimetic silica (28%), the activity recovery was increased 1.86‐fold. TEM, CLSM, magnetisation measurements, and FTIR confirmed that the magnetic nanopaticles and PAL had been co‐encapsulated into the biomimetic silica. The resulting immobilized PAL exhibited higher activity and stability than native PAL, and the immobilized PAL can be easily separated by applying a magnetic field.CONCLUSIONSThis work provides a convenient strategy to prepare stable and easy recycled biocatalyst with excellent catalytic performance. © 2015 Society of Chemical Industry

Silaffins in Silica Biomineralization and Biomimetic Silica Precipitation.

Biomineralization processes leading to complex solid structures of inorganic material in biological systems are constantly gaining attention in biotechnology and biomedical research. An outstanding example for biomineral morphogenesis is the formation of highly elaborate, nano-patterned silica shells by diatoms. Among the organic macromolecules that have been closely linked to the tightly controlled precipitation of silica in diatoms, silaffins play an extraordinary role. These peptides typically occur as complex posttranslationally modified variants and are directly involved in the silica deposition process in diatoms. However, even in vitro silaffin-based peptides alone, with and without posttranslational modifications, can efficiently mediate biomimetic silica precipitation leading to silica material with different properties as well as with encapsulated cargo molecules of a large size range. In this review, the biomineralization process of silica in diatoms is summarized with a specific focus on silaffins and their in vitro silica precipitation properties. Applications in the area of bio- and nanotechnology as well as in diagnostics and therapy are discussed.

Bienzyme system immobilized in biomimetic silica for application in antifouling coatings

Antifouling coatings are used extensively on vessels and underwater structures. Conventional antifouling coatings contain toxic biocides and heavy metals, which may induce unwanted adverse effects such as toxicity to non-target organisms, imposex in gastropods and increased multiresistance among bacteria. Therefore, enzyme-based coatings could be a new alternative solution. A H2O2-producing bienzyme system was developed in this study. H2O2 can be produced from starch by the cooperation of α-amylase and glucose oxidase, which promotes the hydrolysis of polymeric chain and oxidizes the glucose to produce H2O2, respectively. The encapsulated bienzyme (A-G@BS) exhibits enhanced stabilities of thermal, pH, recycling and tolerance of xylene. The A-G@BS-containing coating releases H2O2 at rates exceeding a target of 36nmol·cm−2·d−1 for 90days in a laboratory assay. The results demonstrate that the method is a promising coating technology for entrapping active enzymes, presenting an interesting avenue for enzyme-based antifouling solutions.

Stabilization of Phenylalanine Ammonia Lyase from Rhodotorula glutinis by Encapsulation in Polyethyleneimine-Mediated Biomimetic Silica.

Phenylalanine ammonia lyase (PAL) from Rhodotorula glutinis was encapsulated within polyethyleneimine-mediated biomimetic silica. The main factors in the preparation of biomimetic silica were optimized by response surface methodology (RSM). Compared to free PAL (about 2U), the encapsulated PAL retained more than 43% of their initial activity after 1h of incubation time at 60°C, whereas free PAL lost most of activity in the same conditions. It was clearly indicated that the thermal stability of PAL was improved by encapsulation. Moreover, the encapsulated PAL exhibited the excellent stability of the enzyme against denaturants and storage stability, and pH stability was improved by encapsulation. Operational stability of 7 reaction cycles showed that the encapsulated PAL was stable. Nevertheless, the K m value of encapsulated PAL in biomimetic silica was higher than that of the free PAL due to lower total surface area and increased mass transfer resistance.

Protein-templated biomimetic silica nanoparticles.

Biomimetic silica particles can be synthesized as a nanosized material within minutes in a process mimicked from living organisms such as diatoms and sponges. In this work, we have studied the effect of bovine serum albumin (BSA) as a template to direct the synthesis of silica nanoparticles (NPs) with the potential to associate proteins on its surface. Our approach enables the formation of spheres with different physicochemical properties. Particles using BSA as a protein template were smaller (∼250-380 nm) and were more monodisperse than those lacking the proteic core (∼700-1000 nm) as seen by dynamic light scattering (DLS), scanning electron microscopy (SEM), and environmental scanning electron microscopy (ESEM) analysis. The absence of BSA during synthesis produced silica nanoparticles without any porosity that was detectable by nitrogen adsorption, whereas particles containing BSA developed porosity in the range of 4 to 5 nm which collapsed on the removal of BSA, thus producing smaller pores. These results were in accordance with the pore size calculated by high-resolution transmission electron microscopy (HTEM). The reproducibility of the BSA-templated nanoparticle properties was determined by analyzing four batches of independent synthesizing experiments that maintained their properties. The high positive superficial charge of the nanoparticles facilitated adsorption under mild conditions of a range of proteins from an E. coli extract and a commercial preparation of laccase from Trametes versicolor. All of the proteins were quantitatively desorbed. Experiments conducted showed the reusability of the particles as supports for the ionic adsorption of the biomolecules. The protein loading capacity of the BSA-based biomimetic particles was determined using laccase as 98.7 ± 6.6 mg·g(-1) of particles.

Preparation and application of biomimetic superhydrophobic silica and polyurethane composite coating

A nanosilica (SiO2)/polyurethane (PU) micro-nanocomposite coating with similar surface structure as a lotus leaf was prepared using a simple spraying process via a biomimetic method. In this process, SiO2 and organosilicon-modified PU were used as raw materials, and ethyl acetate was used as a dispersing agent. The formation mechanism and structural characteristics of the coating were analysed. The coating surface was also characterised via scanning electron microscopy. The influence of the contents of SiO2, PU, organosilicon on the coating surface structure and contact angle (CA) was studied and the coating was applied to the surface of different materials. The results showed that the coating surface had a similar micro-nanostructure as the lotus leaf surface. The mass ratio of SiO2 and PU was between 4:5 and 3:5. When the content of organosilicon was greater than 15%, the water CA of the coating and sliding angles were 158° and 3°, respectively. The prepared SiO2/PU micro-nanocomposite coating had superhydrophobic properties.

Immobilising proteins on silica with site-specifically attached modified silaffin peptides

Immobilisation of proteins on solid supports such as silica is commonly applied to improve performance of enzymes under detrimental conditions and to allow enzyme recycling. Silica biomineralisation processes occurring in nature have recently inspired approaches towards mild, biomimetic silica formation. In diatoms, complex posttranslationally modified silaffin peptides are directly involved in formation and patterning of silica cell walls. Here, chemically modified silaffin peptides are used to establish a novel strategy for silica immobilisation of target proteins. Silaffin variants carrying different modifications are covalently linked to eGFP and thioredoxin using expressed protein ligation. Covalent eGFP- and thioredoxin-silaffin conjugates are able to efficiently precipitate silica and control silica properties by choice of different silaffin modifications leading to functional encapsulation of these proteins in silica particles. Covalent protein-silaffin conjugates lead to a distinctly more efficient and homogenous encapsulation of proteins in silica, superior to random protein entrapment resulting from simple co-precipitation. Silica-immobilised proteins are confirmed to be fully active and stabilised against denaturation.

Chitosan-mediated formation of biomimetic silica nanoparticles: An effective method for manganese peroxidase immobilization and stabilization

Our work here, for the first time, reported the use of chitosan-mediated biomimetic silica nanoparticles in enzyme immobilization. In order to make clear the relationship among silicification process, silica nanoparticle structure and immobilized enzyme activity, a mechanism of chitosan-mediated silicification using sodium silicate as the silica source was primarily evaluated. Chitosan was demonstrated effectively to promote the silicification not only in accelerating the aggregation rate of sodium silicate, but also in templating the formation of silica nanoparticles. Although the whole biomimetic silicification process contained polycondensation-aggregation-precipitation three stages, the elemental unit in precipitated silica was confirmed to be nanoparticles with 100nm diameter regardless of the chitosan and silicate concentration used. Furthermore, the effect of enzyme on silicification process was also investigated. The introducing of manganese peroxidase (MnP) to silica precursor solution had no obvious effect on the silicification rate and nanoparticle morphology. The residual activity and embedding rate of immobilized MnP were 64.2% and 36.4% respectively under the optimum conditions. In addition, compared to native MnP, the MnP embedded in chitosan/silica nanoparticles exhibited improved stability against organic solvent and ultrasonic wave. After ultrasonic treatment for 20min, 77% of the initial activity was remained due to the protective effect of chitosan/silica nanoparticles, while native MnP lost almost all of its original activity.

Effects of external force fields on peptide self-assembly and biomimetic silica synthesis

Abstract This study investigated the influence of physical parameters on the dynamic self-assembly of short peptide amphiphiles (A 6 K and V 6 K) and the peptide-mediated silica morphologies by applying external force fields (electric and flow fields). Diverse self-assembled structures (nanofibers, nanorods, or lamellar stacks) can be obtained depending on field intensities and molecular architectures. Although the trend in the structural transitions observed from the electrostatic stimulation differed from that obtained in flow field, the common features indicate that the formed structures exhibit a higher extent of end-to-end merging or lateral association. These self-assembled peptide-based nanostructures then were used as organic templates to tailor silica deposition. It was found that the application of flow fields can stably produce fibril morphology. However, in the case of electric fields, different silica structures were obtained by using different systems. The silica morphologies directed by V 6 K peptide were transformed from fibrils to plate-like structures, and A 6 K peptide produced fibril silica materials. The difference may be attributed to different biomimetic conditions, including external forces, solubility of hydrophobic blocks, and intensity of peptide–silicate interactions. This understanding of the mechanism by which external fields affect the self-assembled amphiphilic peptide nanostructures and the silicification process allows us to manipulate the role of short amphiphilic peptides in silica formation in vitro .