As a new class of bio-abiotic hybrid materials, a series of highly fluorescent self-assembled protein-gold hybrid materials (PGHMs) with different emission wavelengths (blue (B), green (G), yellow (Y), and red (R) colored under UV irradiation) are synthesized by using various combinations of proteins and free amino acids as stabilizer and reducing agents. The synthesis process was controllable by modulating the pH of the reaction solutions. The synthesized PGHMs (PGHM-Blue (PGHM-B), PGHM-Green (PGHM-G), PGHM-Yellow (PGHM-Y), and PGHM-Red (PGHM-R)) exhibited distinct fluorescent properties and showed low cytotoxicity as justified by a bacteria-based test system. The sizes of PGHMs are approximately 100 nm with gold core diameters 0.8–1.8 nm as shown by SEM and TEM images. The assembly of PGHMs was dynamic and occurred through a free radical associated cross-linking process. This general strategy expanded the toolbox of protein-gold hybrid materials. The photostable bio-abiotic hybrid fluorescent nanomaterials can be an alternative to conventional fluorescent probes such as organic dyes and quantum dots for bioimaging studies.

Transformation of DNA into microbial cells via heat-shock approach has been well established in the field of molecular biology for decades. Herein we described an unexpected finding that heat-shock may not play an essential role in the transformation process. This observation was verified via UV-Vis and fluorescence spectroscopies, and confocal microscopy images for various DNAs and bacterial cells. The non-heat-shock approach proposed in this study can be a convenient and beneficial modification for DNA transformation, especially for those laboratories lacking ice machine and heat-shock equipment.

Functional DNA cannot pass through plasma membrane of living cells by itself. An efficient non-viral DNA carrier with low cytotoxicity and simple preparation procedure is in high demand. Herein, we describe that protein–gold hybrid nanocubes (PGHNs) could intrinsically recognize DNAs, and transform them into nanoflower-like structures. These supramolecular complexes can be internalized by living yeast cells and allow the coding information of the gene to be transmitted into proteins. PGHN–DNA can be a good model to study DNA–carrier interactions as well as a new carrier for gene delivery research.

In this report, we describe a new system in which mesoporous silica nanoparticles (MSNs) are gated with α-chymotrypsin A protein (CTRA) and the cargoes within the vehicles are released in the presence of phenylmethanesulfonyl fluoride (PMSF), a canonical inhibitor of CTRA. This cargo release switch is based on the specific interaction between CTRA and PMSF as well as structural changes upon their supramolecular complex formation. This host–guest gating system works smoothly both in vitro and within cells. This type of bio-switch may be extended to other drug carrier systems by using diverse protein–inhibitor pairs that exist in nature.

•AuNCs-p-h were synthesized rapidly within 3 min at approximately 100 °C and contain remarkable peroxidase-like activity.•A facile approach for TP sensing was developed based on the inhibition effect of TPs towards the peroxidase mimic activity of AuNCs-p-h.•This novel sensing system can be readily used for TP quantification from real tea samples.In this report, a rapid approach for the synthesis of protein conjugated gold nanoclusters under heating condition (AuNCs-protein(p)-heating(h)) was proposed. These AuNCs-p-h were synthesized within 3 min at approximately 100 °C and contain remarkable peroxidase-like activity. Notably, in the presence of tea polyphenols (TPs), the peroxidase-like activity of AuNCs-p-h is restrained, which is likely due to the TP-induced aggregation. A facile approach for TP sensing based on the inhibition effect of TPs towards the peroxidase mimic activity of AuNCs-p-h has been developed. Tea is one of the most popular and health beneficial beverages, the favourable effect of which attributes greatly to its key component, TPs. TP detection thus becomes an important task for various food and beverage companies. This novel TP colorimetric detecting method exhibits a linear response in the concentration range of 10 nM to 10 μM with detection limit of 10 nM as well as prominent selectivity towards various TP related molecules including tyrosol, protocatechuate, chlorogenic acid, theophylline, l-theanine, and l-norepinephrine hydrochloride. Comparing with the traditional tartaric acid colorimetric approach (Tac), this new system shows basically identical experimental results but with much higher sensitivity. AuNCs-p-h can be readily used for TP quantification from real tea samples.

Vehicles can deliver the drug molecules into cells, yet immunoreaction of the commonly used capping agents and release triggers limit their biomedical use. This shortcoming might be circumvented through replacing these chemicals with certain biomolecules. Here, we show a new and facile way to encapsulate the drug delivery vehicles and release the cargos in a highly controllable manner via modulating supramolecular interactions between enzyme, substrate, and vehicle. The cargo release from the vehicles within cells can be achieved upon substrate treatment. Yeast cells were used, allowing for a fast and cost-effective way for imaging and morphological analysis. We believe this new platform can be readily extended to various carrier systems for different purposes based on shifting the recognition pattern of enzyme–substrate pairs.Keywords: delivery; enzyme−substrate recognition; living cells; release control; yeast

Multifunctional biocompatible nanomaterials containing both fluorescent and vehicle functions are highly favored in bioimaging, therapeutic, and drug delivery applications. Nevertheless, the rational design and synthesis of highly biocompatible multifunctional materials remain challenging. We present here the development of novel protein–gold hybrid nanocubes (PGHNs), which were assembled using gold nanoclusters, bovine serum albumin, and tryptophan as building blocks. The green-synthesized PGHNs in this study are blue-emitting under UV exposure and cube-shaped with a size of approximately 100 nm. These hybrid nanomaterials are highly biocompatible as shown by cytotoxicity experiments and can be readily internalized by different types of cells. Moreover, PGHNs can act as nanovehicles that successfully deliver dyes or drugs into the cells. The protein–metal hybrid nanocubes can serve as a new type of dual-purpose tool: a blue-emitting cell marker in bioimaging investigation and a nanocarrier in drug delivery studies.Keywords: blue emission; cell imaging; drug delivery; nanovehicle; protein−gold hybrid nanocubes

Carbon dots (CDs) are a new representative in the carbon-based material family, attracting tremendous interest in a large variety of fields, including biomedicine. In this report, we described a facile and green system for synthesizing DNA–CDs using genomic DNA isolated from Escherichia coli. DNA–CDs can be purified using a simple column centrifugation-based system. During DNA–CD synthesis, ribose was collapsed, accompanied by the release of nitrogen, and several new bonds (C–OH, N–O, and N–P) were formed, while the other covalent bonds of DNA were largely maintained. The presence of abundant chemical groups, such as amino or hydroxyl groups on DNA–CDs, may facilitate their future functionalization. These highly biocompatible DNA–CDs can serve as a new type of fluorescent vehicle for cell imaging and drug delivery studies. Our research may hasten the development of CDs for prominent future biomedical applications.Keywords: DNA−carbon dots; drug delivery; fluorescent vehicle; new bond formation

Selective adhesion, growth promotion, proliferation inhibition and in situ transformation of Saccharomyces cerevisiae cells have been realized in a limited space of honeycomb-patterned polystyrene films prepared through a microemulsion method.

Blot-based technology is widely used in biomedical research, serving as a remarkably efficient platform for biomolecule recognition and detection. In this report, highly fluorescent gold nanoclusters have been synthesized under mild conditions by using a proteolytic enzyme, α-chymotrypsin A (CTRA), as both the stabilizing and reducing agents. The synthesized AuNCs@CTRA was characterized by various techniques including UV-vis absorption, fluorescence, X-ray photoelectron spectroscopy and TEM. The fluorescent AuNCs@CTRA is fairly stable and responsive to mercury ions with high selectivity and sensitivity. These protein capped nanoclusters were electrophoresed on an SDS-PAGE gel and transferred to a cellulose membrane. Mercury ions can specifically quench the red fluorescent AuNCs@CTRA band and selectively stop the green band formation on the membrane through inhibition of the peroxidase mimic activity of AuNCs@CTRA toward the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) substrate in a concentration dependent manner. Therefore, using a blot-technology based system, we demonstrated the operation of the AuNCs@CTRA–cellulose hybrid material for mercury ion visual sensing that can be dually read out under UV light (fluorometric) and the naked eye (colorimetric). This approach also has potential for use in other blot-technology based applications.

•DTT capped AuNCs were synthesized at 22 °C and pH 8.•AuNCs@DTT recognizes copper ions with high selectivity and sensitivity.•AuNCs@DTT can be used for the determination of copper ion level in serum.We report here a Green method for the synthesis of fluorescent gold nanoclusters using dithiothreitol (DTT) as both a capping agent and reducing agent at 22 °C and pH 8. The physical and chemical properties of the synthesized AuNCs@DTT were studied by TEM and UV–vis absorption, fluorescence, and X-ray photoelectron spectroscopy. AuNCs@DTT recognizes cupric ions with high selectivity and sensitivity, which allows this material to act as a copper(II) sensor in aqueous solution. A linear relationship was observed between the fluorescence intensity of the DTT capped gold nanoclusters and the concentration of copper(II) ions, in the range of 0–60 μM with a detection limit of 80 nM. The copper content in serum was also analyzed by using this copper sensor. It was shown that data obtained using the proposed method was comparable to values obtained by the traditional colorimetric method. This technique represents an alternative method for the determination of serum copper in clinical diagnosis especially for those laboratories which lack expensive analytical facilities.

Fluorescent gold nanoclusters (AuNCs) were synthesized using a drug target bacterial enoyl-ACP reductase (FabI) as a template. The physical and chemical properties of the AuNCs were studied by UV-vis absorption, fluorescence, X-ray photoelectron spectroscopy and TEM. The AuNCs-FabI conjugate was prepared by in situ reduction of tetrachloroaurate in the presence of FabI. The conjugated particles were loaded onto nylon membranes by taking advantage of the electrostatic interaction between the negatively charged AuNCs@FabI and the nylon film which is positively charged at pH 7.4. This results in the formation of a test stripe with sensor spots that can be used to detect Hg(II) ion in the 1 nM to 10 μM concentration range. The test stripes are simple, convenient, selective, sensitive, and can be quickly read out with bare eyes after illumination with a UV lamp.

Selective adhesion, growth promotion, proliferation inhibition and in situ transformation of Saccharomyces cerevisiae cells have been realized in a limited space of honeycomb-patterned polystyrene films prepared through a microemulsion method.