Enzyme-mimicking nanomaterials (nanozymes) are more cost-effective and robust than protein enzymes, but they lack specificity. Herein, molecularly imprinted polymers were grown on FeO nanozymes with peroxidase-like activity to create substrate binding pockets. Electron microscopy confirmed a shell of nanogel. By imprinting with an adsorbed substrate, moderate specificity was achieved with neutral monomers. Further introducing charged monomers led to nearly 100-fold specificity for the imprinted substrate over the nonimprinted compared to that of bare FeO. Selective substrate binding was further confirmed by isothermal titration calorimetry. The same method was also successfully applied for imprinting on gold nanoparticles (peroxidase mimics) and nanoceria (oxidase mimics). Molecular imprinting furthers the functional enzyme mimicking aspect of nanozymes, and such hybrid materials will find applications in biosensor development, separation, environmental remediation, and drug delivery.
DNA-functionalized gold nanoparticles (AuNPs) are popular hybrid materials with applications in directed assembly, biosensor development, and drug delivery. This system is particularly interesting due to the versatile optical and catalytic properties of AuNPs combined with the molecular recognition and programmable properties of DNA. Instead of emphasizing applications, this review focuses on the interfaces including adsorption of thiol and DNA bases, colloidal stability of AuNPs, and related methods for preparing this conjugate. The effects of salt, pH, proteins, and DNA base composition are discussed for controlling the conformation, density, and stability of DNA. Hybridization of DNA on AuNPs, DNA-directed growing of materials, and cellular uptake of this conjugate are discussed as examples to highlight the importance of the interfaces. Our understanding of these biointerfaces is still far from complete, and a few future research opportunities for engineering hybrid materials are described.
In a typical protocol for attaching DNA to a gold electrode, thiolated DNA is incubated with the electrode at neutral pH overnight. Here we report fast adsorption of non-thiolated DNA oligomers on gold electrodes at acidic pH (i.e., pH ~3.0). The peak-to-peak potential difference and the redox peak currents in typical cyclic voltammetry of [Fe(CN)6] 3-are investigated to monitor the attachment. Compared with incubation at neutral pH, the lower pH can significantly promote the adsorption processes, enabling efficient adsorption even in 30 min. The adsorption rate is DNA concentration-dependent, while the ionic strength shows no influence. Moreover, the adsorption is base-discriminative, with a preferred order of A >C>>G, T, which is attributed to the protonation of A and C at low pH and their higher binding affinity to gold surface. The immobilized DNA is functional and can hybridize with its complementary DNA but not a random DNA. This work is promising to provide a useful time-saving strategy for DNA assembly on gold electrodes, allowing fast fabrication of DNA-based biosensors and devices.3
Abstract. Precipitation of DNA from a large volume of aqueous solution is an important step in many molecular biology and analytical chemistry experiments. Currently, this is mainly achieved by ethanol precipitation, where a long-term incubation (usually overnight) at low temperature of -20 to -80 C with high salt concentration is required. This method also requires a large quantity of DNA to form a visible pellet and was tested mainly for double-stranded DNA. To improve DNA precipitation, coprecipitating polymers such as linear polyacrylamide has been used. In this work, we report that starch nanoparticles (SNPs) can achieve convenient DNA precipitation at room temperature with a low salt concentration and short incubation time. This method requires as low as 0.01-0.1% SNPs and can precipitate both single-and double-stranded DNA of various lengths. The effect of salt concentration, pH and the crosslinking density of SNPs has been systematically studied. Compared to other types of precipitating agents, SNPs are highly biocompatible and can be degraded by a common enzyme (amylase). This work suggests a novel application of a bio-based material that is prepared in mass production.
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