Improvement in the Thermal Stability of Pyrophosphatase by Conjugation to Poly(N-isopropylacrylamide): Application to the Polymerase Chain Reaction

Pathogenic Bacteria Detection Using RNA-Based Loop-Mediated Isothermal-Amplification-Assisted Nucleic Acid Amplification via Droplet Microfluidics

Nucleic acid amplifications, such as polymerase chain reaction (PCR), are very beneficial for diagnostic applications, especially in the context of bacterial or viral outbreaks due to their high specificity and sensitivity. However, the need for bulky instrumentation and complicated protocols makes these methods expensive and slow, particularly for low numbers of RNA or DNA templates. In addition, implementing conventional nucleic acid amplification in a high-throughput manner is both reagent- and time-consuming. We bring droplet-based microfluidics and loop-mediated isothermal amplification (LAMP) together in an optimized operational condition to provide a sensitive biosensor for amplifying extracted RNA templates for the detection of Salmonella typhimurium (targeting the invA gene). By simultaneously performing ∼10⁶ LAMP-assisted amplification reactions in picoliter-sized droplets and applying a new mathematical model for the number of droplets necessary to screen for the first positive droplet, we study the detection limit of our platform with pure culture and real samples (bacterial contaminated milk samples). Our LAMP-assisted droplet-based microfluidic technique was simple in operation, sensitive, specific, and rapid for the detection of pathogenic bacteria Salmonella typhimurium in comparison with well-established conventional methods. More importantly, the high-throughput nature of this technique makes it suitable for many applications in biological assays.

Gold nanoparticle–protein conjugate dually-responsive to pH and temperature for modulation of enzyme activity

The enzymatic activity of the dual-responsive gold nanoparticle–protein–polymer conjugate can be modulated almost in a full range under different pH and temperature conditions.

An update on smart biocatalysts for industrial and biomedical applications

Recently, smart biocatalysts, where enzymes are conjugated to stimuli-responsive (smart) polymers, have gained significant attention. Based on the presence or absence of external stimuli, the polymer attached to the enzyme changes its conformation to protect the enzyme from the external environment and regulate the enzyme activity, thus acting as a molecular switch. Owing to this behaviour, smart biocatalysts can be separated easily from a reaction mixture and re-used several times. Several such smart polymer-based biocatalysts have been developed for industrial and biomedical applications. In addition, they have been used in biosensors, biometrics and nano-electronic devices. This review article covers recent advances in developing different kinds of stimuli-responsive enzyme bioconjugates, including conjugation strategies, and their applications.

A photosensitizer loaded hemoglobin–polymer conjugate as a nanocarrier for enhanced photodynamic therapy

A hemoglobin–polymer conjugate (HbTcMs) with oxygen supply was applied to generate more singlet oxygen for enhanced photodynamic therapy.

Multifunctional gold nanoparticle layers for controllable capture and release of proteins

Protein modified functional surfaces have been applied extensively in the field of biomaterials and medicine. Regulation of the amount and activity of proteins on the material surface is always a challenge and a key research issue. A multifunctional micro/nano-composite based surface system for efficient controllable capture and release of proteins is proposed and studied in the present paper. This novel system contains (1) gold nanoparticles (AuNPs) co-modified with an enzyme and poly(methacrylic acid) (PMAA), e.g., AuNP-pyrophosphatase (PPase)-PMAA, as nanostructured protein carriers; (2) gold nanoparticle layers (GNPLs) modified with poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA), i.e., GNPL-PDMAEMA, as a micro/nano-structured support platform for surface bioactivity regulation. The capture-release of proteins and the regulation of surface bioactivity in this composite surface system were investigated under different conditions. The results showed that the proposed system is capable of protein capture and release with simple adjustment of the pH value from neutral pH to basic pH. When the pH of the system is stabilized at 7.0, the GNPL-PDMAEMA surface could adsorb plenty of AuNP-PPase-PMAA conjugates and maximum surface bioactivity occurred, but when the pH of the system is adjusted to 10.0, the GNPL-PDMAEMA surface could liberate almost all the AuNP-PPase-PMAA conjugates and thus surface bioactivity disappeared. Meanwhile, by cyclical variations between pH 7.0 and pH 10.0, this surface protein capture/release system could realize recycling and reuse of one certain protein multiple times, a series of proteins acting sequentially in accordance with pre-designed procedures, and a functional combination of multiple proteins. This recyclable multifunctional surface with the capability of protein capture/release has great potential in many applications, such as biomonitoring and biomolecule immobilization.

Nano-thin walled micro-compartments from transmembrane protein-polymer conjugates

The high interfacial activity of protein-polymer conjugates has inspired their use as stabilizers for Pickering emulsions, resulting in many interesting applications such as synthesis of templated micro-compartments and protocells or vehicles for drug and gene delivery. In this study we report, for the first time, the stabilization of Pickering emulsions with conjugates of a genetically modified transmembrane protein, ferric hydroxamate uptake protein component A (FhuA). The lysine residues of FhuA with open pore (FhuA ΔCVF^tev) were modified to attach an initiator and consequently controlled radical polymerization (CRP) carried out via the grafting-from technique. The resulting conjugates of FhuA ΔCVF^tev with poly(N-isopropylacrylamide) (PNIPAAm) and poly((2-dimethylamino)ethyl methacrylate) (PDMAEMA), the so-called building blocks based on transmembrane proteins (BBTP), have been shown to engender larger structures. The properties such as pH-responsivity, temperature-responsivity and interfacial activity of the BBTP were analyzed using UV-Vis spectrophotometry and pendant drop tensiometry. The BBTP were then utilized for the synthesis of highly stable Pickering emulsions, which could remain non-coalesced for well over a month. A new UV-crosslinkable monomer was synthesized and copolymerized with NIPAAm from the protein. The emulsion droplets, upon crosslinking of polymer chains, yielded micro-compartments. Fluorescence microscopy proved that these compartments are of micrometer scale, while cryo-scanning electron microscopy and scanning force microscopy analysis yielded a thickness in the range of 11.1 ± 0.6 to 38.0 ± 18.2 nm for the stabilizing layer of the conjugates. Such micro-compartments would prove to be beneficial in drug delivery applications, owing to the possibility of using the channel of the transmembrane protein as a gate and the smart polymer chains as trigger switches to tune the behavior of the capsules.

Controlled protein adsorption and delivery of thermosensitive poly(N-isopropylacrylamide) nanogels

Controlled protein adsorption and delivery of thermosensitive poly(N-isopropylacrylamide) nanogels by tailoring the temperature and pH value of the medium.

Silica-coated triangular gold nanoprisms as distance-dependent plasmon-enhanced fluorescence-based probes for biochemical applications

Plasmon-enhanced fluorescence (PEF)-based anisotropic nanostructures are considered extremely promising tools for improving the inherent problems of traditional fluorophores and for detecting important biomolecules with high sensitivity. Herein, a novel triangular gold nanoprism (AuNPR)-based fluorescence probe, AuNPR@SiO₂@12,17-tetramethyl-3-dihydro-(2s-trans)-thyl-7(Ce6), was developed for PEF by virtue of multiple "hot spots" of AuNPRs. Fluorescence enhancement of fluorophores can be realized owing to the larger and stronger electromagnetic fields located at the sharp tips of AuNPRs than those on spherical particles and nanorods. A silica shell was employed as a rigid spacer to precisely adjust the distance between the AuNPR and Ce6 for optimal PEF. Owing to the improved fluorescence signal, core-shell PEF-based AuNPRs can be applied as a turn-on probe for highly selective and sensitive detection of pyrophosphate (PPi) with a desirable detection limit of 0.2 μM using a displacement approach. Meanwhile, we demonstrated that these nanomaterials have great potential for real-time monitoring of polymerase chain reaction (PCR) products, successfully revealing an approximately 240 times higher detectable fluorescence response than that of traditional gel electrophoresis. Furthermore, cell imaging indicates the potential applications of PEF-based probes in living cells.

Improvement of Site-Directed Protein-Polymer Conjugates: High Bioactivity and Stability Using a Soft Chain-Transfer Agent

Protein has been widely applied in biotechnology and biomedicine thanks to its unique properties of high catalytic activity, outstanding receptor-ligand specificity, and controllable sequence mutability. Owing to the easily induced structural variation and thus the inactivation of protein, there has been much effort to improve the structural stability and biological activity of proteins by the use of polymers to modify protein to construct protein-polymer conjugates. However, during the conjugation of polymer to protein active center, the great loss in the original biological activity of the protein is still a serious and so far unsolved question. Here, for the purpose of preparing site-directed and highly structurally stable protein-polymer conjugate, which would possess at least a substantially similar level of biological activity as the original unmodified protein, we proposed a new strategy by using a pyridine chain-transfer agent (CTA-Py) with a soft pyridine-terminated chain for visible-light-induced reversible addition-fragmentation chain transfer (RAFT) polymerization specifically on a number of sites close to the protein active center. The results showed that all the intermediate conjugates PPa-CTA-Py at different modification sites could retain full enzymatic activities (about 110-130% of the unmodified PPa). It was demonstrated by dynamic computer simulation that introducing of CTA-Py had little interference to the protein spatial structure as compared to the popular maleimide chain-transfer agent (CTA-Ma) with rigid maleimide-terminated. Moreover, intermediate conjugates PPa-CTA-Py is facile and ready for further light polymerization under mild conditions. Final PPa-PNIPAAm conjugate produced from CTA-Py exhibited excellent temperature responsiveness and maintained its enzymatic activity even at high temperature. These highly stable and responsive protein-polymer conjugates have great potential and could be widely used in various industrial, chemical, biological, and pharmaceutical applications.

Design of Self-Assembling Protein-Polymer Conjugates

Protein-polymer conjugates are of particular interest for nanobiotechnology applications because of the various and complementary roles that each component may play in composite hybrid-materials. This chapter focuses on the design principles and applications of self-assembling protein-polymer conjugate materials. We address the general design methodology, from both synthetic and genetic perspective, conjugation strategies, protein vs. polymer driven self-assembly and finally, emerging applications for conjugate materials. By marrying proteins and polymers into conjugated bio-hybrid materials, materials scientists, chemists, and biologists alike, have at their fingertips a vast toolkit for material design. These inherently hierarchical structures give rise to useful patterning, mechanical and transport properties that may help realize new, more efficient materials for energy generation, catalysis, nanorobots, etc.

Protein–polymer conjugates prepared via host–guest interactions: effects of the conjugation site, polymer type and molecular weight on protein activity

Protein–polymer conjugates are prepared via host–guest interactions and the effects of various parameters on protein activity are investigated.

One-step synthesis of glycoprotein mimics in vitro: improvement of protein activity, stability and application in CPP hydrolysis

Glycoprotein mimics produced in vitro by one-step conjugation of glycopolymer and pyrophosphatase have improved bioactivity and stability for potential biomedical applications.