Calcium carbonate nanoparticles: a host matrix for the construction of highly sensitive amperometric phenol biosensor

Multifaceted Materials for Enhanced Osteogenesis and Antimicrobial Properties on Bioplastic Polyetheretherketone Surfaces: A Review

Implant-associated infections and the increasing number of bone implants loosening and falling off after implantation have become urgent global challenges, hence the need for intelligent alternative solutions to combat implant loosening and falling off. The application of polyetheretherketone (PEEK) in biomedical and medical therapy has aroused great interest, especially because its elastic modulus close to bone provides an effective alternative to titanium implants, thereby preventing the possibility of bone implants loosening and falling off due to the mismatch of elastic modulus. In this Review, we provide a comprehensive overview of recent advances in surface modifications to prevent bone binding deficiency and bacterial infection after implantation of bone implants, starting with inorganics for surface modification, followed by organics that can effectively promote bone integration and antimicrobial action. In addition, surface modifications derived from cells and related products of biological activity have been proposed, and there is increasing evidence of clinical potential. Finally, the advantages and future challenges of surface strategies against medical associated poor osseointegration and infection are discussed, with promising prospects for developing novel osseointegration and antimicrobial PEEK materials.

A Robust Triboelectric Impact Sensor with Carbon Dioxide Precursor-Based Calcium Carbonate Layer for Slap Match Application

As an urgent international challenge, the sudden change in climate due to global warming needs to be addressed in the near future. This can be achieved through a reduction in fossil fuel utilization and through carbon sequestration, which reduces the concentration of CO2 in the atmosphere. In this study, a self-sustainable impact sensor is proposed through implementing a triboelectric nanogenerator with a CaCO3 contact layer fabricated via a CO2 absorption method. The triboelectric polarity of CaCO3 with the location between the polyimide and the paper and the effects of varying the crystal structure are investigated first. The impact sensing characteristics are then confirmed at various input frequencies and under applied forces. Further, the high mechanical strength and strong adherence of CaCO3 on the surface of the device are demonstrated through enhanced durability compared to the unmodified device. For the intended application, the as-fabricated sensor is used to detect the turning state of the paper Ddakji in a slap match game using a supervised learning algorithm based on a support vector machine presenting a high classification accuracy of 95.8%. The robust CaCO3-based triboelectric device can provide an eco-friendly advantage due to its self-powered characteristics for impact sensing and carbon sequestration.

Effect of amino acids on biomineralization of lead ions by Aspergillus niger

This study investigates the biomineralization of lead ions by Aspergillus niger from aqueous environments, focusing on the dynamic effects of fungal metabolism and biological components. Three biomolecules (glutamate, methionine, and lysine) were used to induce lead oxalate mineralization under lead stress. Comparative experiments were conducted to analyze the growth characteristics and Pb (II) removal ability of A. niger, as well as the morphological and structural properties of the resulting lead oxalate minerals using inductively coupled plasma atomic emission spectroscopy, X-ray powder diffraction, and scanning electron microscopy-energy dispersive spectroscopy techniques. The findings reveal that A. niger plays a crucial role in controlling the mineralization process of Pb (II), with biomineralization experiments demonstrating the specific morphogenesis of lead oxalate over time. Additionally, the inclusion of the three biomolecules in the system indirectly influenced the rate of Pb (II) removal and mineral morphology. These results contribute to a better understanding of A. niger-mediated biomineralization process of lead oxalate and suggest its potential application in the removal of Pb (II) from aqueous environments, particularly in combination with amino acids for enhanced immobilization and mineral recovery. PRACTITIONER POINTS: Fungal activity and amino acids play a crucial role in shaping lead oxalate crystals during water treatment processes. Specific amino acids can effectively delay lead oxalate recrystallization, enhancing the stability and removal efficiency of the crystals. Biomineralization mediated by fungi offers a promising and eco-friendly approach for lead removal and recovery in wastewater treatment. Exploring the influence of organic additives and fungal metabolism on crystal growth provides valuable insights for developing efficient remediation strategies. Further research on the utilization of fungi and amino acids can help with innovative and sustainable wastewater treatment technologies.

Comparison of Physicochemical Properties of Noodles Fortified with Commercial Calcium Salts versus Calcium Citrate from Oyster Shells

This study examined the physicochemical effects of the fortification of noodles with 0.25-1.00% (w/w) calcium salts, viz. calcium acetate, calcium carbonate, calcium citrate, and calcium lactate. Fortification with calcium citrate, calcium acetate, and calcium carbonate increased the pH and breaking force of the dried noodles. However, the fortification of noodles with any concentration of calcium did not increase the extent of elongation of the control raw noodles. The L* and b* values of the raw and dried noodle color increased with increasing concentrations of calcium salts, except for noodles with added calcium citrate. Fortification with calcium citrate yielded no significant influence on color, texture, adhesiveness, springiness, flavor, and overall scores for cooked noodles. Noodles fortified with 0.5% calcium citrate made from oyster shells were compared with a control sample of noodles and noodles fortified with commercially available calcium citrate. The particle size of the calcium citrate made from oyster shells (258 nm) was smaller than that of the purchased calcium citrate (2631 nm). Noodles fortified with calcium citrate made from oyster shells showed no significantly difference compared to noodles fortified with commercially available calcium citrate. These results suggest that calcium citrate made from oyster shells may be used as the additive of choice for the manufacture of calcium-fortified noodles.

Calcium carbonate nano- and microparticles: synthesis methods and biological applications

Calcium carbonate micro- and nanoparticles are considered as chemically inert materials. Therefore, they are widely considered in the field of biosensing, drug delivery, and as filler material in plastic, paper, paint, sealant, and adhesive industries. The unusual properties of calcium carbonate-based nanomaterials, such as biocompatibility, high surface-to-volume ratio, robust nature, easy synthesis, and surface functionalization, and ability to exist in a variety of morphologies and polymorphs, make them an ideal candidate for both industrial and biomedical applications. Significant research efforts have been devoted for developing novel synthesis methods of calcium carbonate particles in micrometer and nanometer dimensions. This review highlights different approaches of the synthesis of calcium carbonate micro- and nanoparticles, such as precipitation, slow carbonation, emulsion, polymer-mediated method, including in-situ polymerization, mechano-chemical, microwave-assisted method, and biological methods. The applications of these versatile calcium carbonate micro- and nanoparticles in the biomedical field (such as in drug delivery, therapeutics, tissue engineering, antimicrobial activity, biosensing applications), in industries, and environmental sector has also been comprehensively covered.

Functionalized tungsten disulfide nanotubes for dopamine and catechol detection in a tyrosinase-based amperometric biosensor design

WS2 nanotubes functionalized with carboxylic acid functions (WS2-COOH) were used for improved immobilization of the enzyme tyrosinase in order to form an electrochemical biosensor towards catechol and dopamine. The nanotubes were deposited on glassy carbon electrodes using a dispersion-filtration-transfer procedure to assure the reproducibility of the deposits. After the electrochemical and morphological characterization of these WS2-COOH nanotube deposits, the formed biosensors showed very satisfying performance towards catechol detection with a linear range of 0.6-70 μmol L-1 and a sensitivity of 10.7 ± 0.2 mA L mol-1. The apparent Michaelis Menten constant of this system is slightly lower than the KM value of tyrosinase in solution, reflecting an excellent accessibility of the active site of the enzyme combined with a good mass transport of the target molecule through the deposit. For dopamine detection, we observed an accumulation of this substrate due to electrostatic interactions between the amine function of dopamine and the carboxylic acid groups of the nanotubes. This led to improved signal capture at low dopamine concentrations. With linear ranges of 0.5-10 μmol L-1 and 10-40 μmol L-1, and respective sensitivities of 6.2 ± 0.7 mA L mol-1 and 3.4 ± 0.4 mA L mol-1, the overall sensor performance is within the average of comparable results using carbon nanotubes. Nonetheless, the simplified handling of these nanotubes and their reduced environmental impact make these WS2-COOH nanotubes a promising nanomaterial for biosensing applications.

Variations and similarities in structural, chemical, and elemental properties on the ashes derived from the coal due to their combustion in open and controlled manner

Coal fly ash (CFA) and coal-based incense sticks ash (ISA) have several similarities and differences due to the presence of coal as a common component in both of them. CFA are produced from the combustion of pulverized coal during electricity production in the thermal power plants while ISA are produced from the burning of incense sticks at religious places and at houses. A typical black colored Indian, incense sticks are mainly are comprised of coal powder or potassium nitrate, wood chip, fragrance, binder or binding agent, and bamboo sticks. The black colored incense sticks have coal powder or charcoal as a facilitator for smoother burning of incense sticks. The detailed investigation of CFA and ISA by X-ray fluorescence spectroscopy (XRF), electron diffraction spectroscopy (EDS), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), Fourier transform-infrared (FTIR), X-ray diffraction (XRD), particle size analyzer (PSA), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) revealed the morphological, chemical, and elemental properties. Both the coal based ashes comprises minerals like calcites, silicates, ferrous, alumina, and traces of Mg, Na, K, P, Ti, and numerous toxic heavy metals as confirmed by the XRF, ICP-AES, and EDS. While, microscopy revealed the presence of well-organized spherical shaped particles, namely cenospheres, plerospheres, and ferrospheres of size varying from 0.02 μm to 7 microns in CFA. Whereas, ISA particles are irregular, aggregated, calcium to carbon rich whose size varies from 60 nm to 9 microns and absence of well-organized spherical structures. The well developed and crystalline structure in CFA is due to the controlled combustion parameter in thermal power plants during the burning of coal while incense sticks (IS) burning is under uncontrolled manner. So, FTIR and XRD confirmed that the major portion of fly ash constitutes crystalline minerals whereas ISA have mainly amorphous phase minerals. CFA have ferrospheres of both rough and smooth surfaced, which was absent from the ISA and hence ferrous particles of CFA are of high magnetic strength. The detailed investigation of ashes will lead to the applications of ashes in new fields, which will minimize the solid waste pollution in the environment.

Mesoporous carbon nitride based biosensor for highly sensitive and selective analysis of phenol and catechol in compost bioremediation

Herein, we reported here a promising biosensor by taking advantage of the unique ordered mesoporous carbon nitride material (MCN) to convert the recognition information into a detectable signal with enzyme firstly, which could realize the sensitive, especially, selective detection of catechol and phenol in compost bioremediation samples. The mechanism including the MCN based on electrochemical, biosensor assembly, enzyme immobilization, and enzyme kinetics (elucidating the lower detection limit, different linear range and sensitivity) was discussed in detail. Under optimal conditions, GCE/MCN/Tyr biosensor was evaluated by chronoamperometry measurements and the reduction current of phenol and catechol was proportional to their concentration in the range of 5.00 × 10(-8)-9.50 × 10(-6)M and 5.00 × 10(-8)-1.25 × 10(-5)M with a correlation coefficient of 0.9991 and 0.9881, respectively. The detection limits of catechol and phenol were 10.24 nM and 15.00 nM (S/N=3), respectively. Besides, the data obtained from interference experiments indicated that the biosensor had good specificity. All the results showed that this material is suitable for load enzyme and applied to the biosensor due to the proposed biosensor exhibited improved analytical performances in terms of the detection limit and specificity, provided a powerful tool for rapid, sensitive, especially, selective monitoring of catechol and phenol simultaneously. Moreover, the obtained results may open the way to other MCN-enzyme applications in the environmental field.

Optimization of process parameters of polymer solution mediated growth of calcium carbonate nanoparticles

With the advent of nanotechnology, many methods of synthesis of nanoparticles have come into practice and the 'polymer mediated growth' technique is among them. In this route, ions of one of the reactants are allowed to diffuse from an external solution into a polymer matrix where the other reactant is complexed and bound. The exact role of ionic diffusion in the formation of nanoparticles was investigated in the current study by studying the patterns of kinetics of nanoparticle formation using UV vis spectroscopy. Typically, calcium carbonate nanoparticles were formed by the aforementioned technique using polyethylene glycol solution. The particle size was calculated using Scherrer's formula on x-ray diffraction plots and was reconfirmed with field emission scanning electron microscope and transmission electron microscope images. Energy-dispersive x-ray analysis was used to study the composition and purity of the nanoparticles formed. The reactant to polymer ratio, reaction temperature and molecular weight of polyethylene glycol affected the size of the particles formed. Through this knowledge we optimized these parameters to obtain particles as small as 20 nm and confirmed that this technique can be used to control the size of nanoparticles.

Effect of cationic polyacrylamide adsorption kinetics and ionic strength on precipitated calcium carbonate flocculation

The effect of polymer adsorption kinetics and ionic strength on the dynamics of particle flocculation was quantified using a model system consisting of precipitated calcium carbonate (PCC) and cationic polyacrylamide (CPAM) at a low shear rate. All early flocculations detectable by a photodispersion analyzer (PDA) happened in nonequilibrium polymer adsorption regimes. We observed discrepancies in flocculation rates with the surface coverage theory, which is based on a simple monolayer adsorption model, in both early and late flocculation stages. For instance, the same amount of adsorbed CPAM reached at different polymer doses demonstrated different flocculating capabilities. This highlighted the importance of polymer adsorption kinetics upon flocculation. The transient conformation of the adsorbed CPAM during the kinetic process sometimes even superceded the adsorbed amount in the determination of PCC flocculation. Both antagonistic and synergetic effects of increased ionic strength on the CPAM-induced PCC aggregation were observed during early flocculation. However, late-stage PCC flocculation shared some similarities, irrespective of polymer dose and ionic strength. Despite the decreased amount of adsorbed polymer from the increased ionic strength, the combination of CPAM and salt, at certain concentrations, demonstrated a synergy to promote PCC aggregation more efficiently than the same amount of the respective components.

Biosensing applications of clay-modified electrodes: a review

Two-dimensional layered inorganic solids, such as cationic clays and layered double hydroxides (LDHs), also defined as anionic clays, have open structures which are favourable for interactions with enzymes and which intercalate redox mediators. This review aims to show the interest in clays and LDHs as suitable host matrices likely to immobilize enzymes onto electrode surfaces for biosensing applications. It is meant to provide an overview of the various types of electrochemical biosensors that have been developed with these 2D layered materials, along with significant advances over the last several years. The different biosensor configurations and their specific transduction procedures are discussed.

Biosensors for phenolic compounds by immobilization of tyrosinase in photocurable methacrylic-acrylic membranes of varying hydrophilicities

Electrochemical biosensors for phenolic compound determination were developed by immobilization of tyrosinase enzyme in a series of methacrylic-acrylic based biosensor membranes deposited directly using a photocuring method. By modifying the hydrophilicity of the membranes using different proportions of 2-hydroxyethyl methacrylate (HEMA) and butyl acrylate (nBA), we developed biosensor membranes of different hydrophilic characters. The differences in hydrophilicity of these membranes led to changes in the sensitivity of the biosensors towards different phenolic compounds. In general biosensors constructed from the methacrylic-acrylic based membranes showed the poorest response to catechol relative to other phenolic compounds, which is in contrast to many other biosensors based on tyrosinase. The decrease in hydrophilicity of the membrane also allowed better selectivity towards chlorophenols. However, phenol biosensors constructed from the more hydrophilic membrane materials demonstrated better analytical performance towards phenol compared with those made from less hydrophilic ones. For the detection of phenols, these biosensors with different membranes gave detection limits of 0.13-0.25 microM and linear response range from 6.2-54.2 microM phenol. The phenol biosensors also showed good phenol recovery from landfill leachate samples (82-117%).

Recent advances in nanotechnology applied to biosensors

In recent years there has been great progress the application of nanomaterials in biosensors. The importance of these to the fundamental development of biosensors has been recognized. In particular, nanomaterials such as gold nanoparticles, carbon nanotubes, magnetic nanoparticles and quantum dots have been being actively investigated for their applications in biosensors, which have become a new interdisciplinary frontier between biological detection and material science. Here we review some of the main advances in this field over the past few years, explore the application prospects, and discuss the issues, approaches, and challenges, with the aim of stimulating a broader interest in developing nanomaterial-based biosensors and improving their applications in disease diagnosis and food safety examination.

Effects of Gold Nanoparticles on the Response of Phenol Biosensor Containing Photocurable Membrane with Tyrosinase

The role of incorporation of gold nanoparticles (50-130 nm in diameter) into a series of photocurable methacrylic-acrylic based biosensor membranes containing tyrosinase on the response for phenol detection was investigated. Membranes with different hydrophilicities were prepared from 2-hydroxyethyl methacrylate and n-butyl acrylate via direct photocuring. A range of gold nanoparticles concentrations from 0.01 to 0.5 % (w/w) was incorporated into these membranes during the photocuring process. The addition of gold nanoparticles to the biosensor membrane led to improvement in the response time by a reduction of approximately 5 folds to give response times of 5-10 s. The linear response range of the phenol biosensor was also extended from 24 to 90 mM of phenol. The hydrophilicities of the membrane matrices demonstrated strong influence on the biosensor response and appeared to control the effect of the gold nanoparticles. For less hydrophilic methacrylic-acrylic membranes, the addition of gold nanoparticles led to a poorer sensitivity and detection limit of the biosensor towards phenol. Therefore, for the application of gold nanoparticles in the enhancement of a phenol biosensor response, the nanoparticles should be immobilized in a hydrophilic matrix rather than a hydrophobic material.