Choon Peng Teng

Protein Induces Layer-by-Layer Exfoliation of Transition Metal Dichalcogenides

Here, we report a general and facile method for effective layer-by-layer exfoliation of transition metal dichalcogenides (TMDs) and graphite in water by using protein, bovine serum albumin (BSA) to produce single-layer nanosheets, which cannot be achieved using other commonly used bio- and synthetic polymers. Besides serving as an effective exfoliating agent, BSA can also function as a strong stabilizing agent against reaggregation of single-layer nanosheets for greatly improving their biocompatibility in biomedical applications. With significantly increased surface area, single-layer MoS2 nanosheets also exhibit a much higher binding capacity to pesticides and a much larger specific capacitance. The protein exfoliation process is carefully investigated with various control experiments and density functional theory simulations. It is interesting to find that the nonpolar groups of protein can firmly bind to TMD layers or graphene to expose polar groups in water, facilitating the effective exfoliation of single-layer nanosheets in aqueous solution. The present work will enable to optimize the fabrication of various 2D materials at high yield and large scale, and bring more opportunities to investigate the unique properties of 2D materials and exploit their novel applications.

Effective near-infrared photodynamic therapy assisted by upconversion nanoparticles conjugated with photosensitizers

A drug model photosensitizer-conjugated upconversion nanoparticles nanocomplex was explored for application in near-infrared photodynamic therapy. As near-infrared penetrates deeper into the tissue, the model is useful for the application of photodynamic therapy in deeper tissue. The nanocomplex that was synthesized had low polydispersity, and the upconversion nanoparticle was covalently conjugated with the photosensitizer. The robust bond could prevent the undesired premature release of photosensitizer and also enhance the singlet-oxygen generation. Singlet-oxygen generation rate from this nanocomplex was evaluated in solution. The photodynamic therapy effect was assessed with MCF-7 cells in two different methods, 3-(4,5-dimethylth-iazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and live/dead assay. The assay results showed that promising efficacy (>90%) can be achieved with a low concentration (50 μg mL(-1)) of this nanocomplex and mild dosage (7 mW cm(-2)) of near-infrared laser treatment.

Plasmonic gold nanocrosses with multidirectional excitation and strong photothermal effect.

We report a facile chemical synthesis of well-defined gold nanocrosses through anisotropic growth along both <110> and <001>, whereas gold nanorods grow only along either <110> or <001>. The multiple branching was achieved by breaking the face-centered-cubic lattice symmetry of gold through copper-induced formation of single or double twins, and the resulting gold nanocrosses exhibited pronounced near-IR absorption with a great extension to the mid-IR region. As studied by discrete dipole approximation (DDA) simulations, the entire nanocross gets excited even when one of the branches is exposed to incident light. The above properties make them useful as octopus antennas for capturing near-IR light for effective photothermal destruction of cells. The cell damage process was analyzed using the Arrhenius model, and its intrinsic thermodynamic characteristics were determined quantitatively. Besides effective photothermal treatment and two-photon luminescence imaging, the near- and mid-IR-absorbing gold nanocrosses may also find applications in IR sensing, thermal imaging, telecommunications, and the like.

Intrinsically Colored and Luminescent Silk

A IO N Silk has been a highly prized material since its discovery a few thousand years ago, with a current annual industrial output of approximately 30 billion US dollars in China alone. [ 1 , 2 ] In silk industry, the outer layer of silk (sericin) needs to be removed in order to use the core of silk (fi broin) that has excellent mechanical properties combined with luster, smoothness, and comfort. To impart color to the fi nished products, silk fi broin is subjected to the dyeing process including steps to remove excess dye molecules and to restore the properties of silk that are altered due to the harsh conditions involved in the process. [ 3 ] Here, we demonstrate an in vivo uptake of dyes into domesticated silkworms, leading to the direct production of intrinsically colored silk by the silkworms. The biological incorporation of dyes into silk fi broin is a greener method of producing colored silk because it eliminates the need for an external dyeing process, along with the resources (water, energy, additional chemicals) and post-treatments associated with it. A series of fl uorescent dyes were successfully used as model compounds to investigate and understand their selective uptake into fi broin or sericin through fl uorescence imaging and spectroscopic quantifi cation. A better understanding of the molecular factors that determine the uptake of substances into silk fi broin was established to select and design appropriate molecules for producing intrinsically colored and luminescent silk fi broin, i.e., by controlling the structure-dependent hydrophobicity and self-assembly capability of these molecules. In addition to the production of intrinsically colored silk for textile applications, the current work also results in a biocompatible and luminescent silk scaffold that allows better visualization of cells and monitoring of the scaffold performance over time. When applied to other compounds with similar molecular properties, this process can potentially lead to functional silk for various biomedical applications including tissue engineering and bioelectronic, bio-optic, and biomicrofl uidic devices. [ 4–6 ]

Recent Progress in Energy-Driven Water Splitting

Hydrogen is readily obtained from renewable and non‐renewable resources via water splitting by using thermal, electrical, photonic and biochemical energy. The major hydrogen production is generated from thermal energy through steam reforming/gasification of fossil fuel. As the commonly used non‐renewable resources will be depleted in the long run, there is great demand to utilize renewable energy resources for hydrogen production. Most of the renewable resources may be used to produce electricity for driving water splitting while challenges remain to improve cost‐effectiveness. As the most abundant energy resource, the direct conversion of solar energy to hydrogen is considered the most sustainable energy production method without causing pollutions to the environment. In overall, this review briefly summarizes thermolytic, electrolytic, photolytic and biolytic water splitting. It highlights photonic and electrical driven water splitting together with photovoltaic‐integrated solar‐driven water electrolysis.

Effective Targeted Photothermal Ablation of Multidrug Resistant Bacteria and Their Biofilms with NIR-Absorbing Gold Nanocrosses.

With the rapid evolution of antibiotic resistance in bacteria, antibiotic-resistant bacteria (in particular, multidrug-resistant bacteria) and their biofilms have been becoming more and more difficult to be effectively treated with conventional antibiotics. As such, there is a great demand to develop a nonantibiotic approach in efficiently eliminating such bacteria. Here, multibranched gold nanocrosses with strong near-infrared absorption falling in the biological window, which heat up quickly under near-infrared-light irradiation are presented. The gold nanocrosses are conjugated to secondary and primary antibodies for targeting PcrV, a type III secretion protein, which is uniquely expressed on the bacteria superbug, Pseudomonas aeruginosa. The conjugated gold nanocrosses are capable of completely destroying P. aeruginosa and its biofilms upon near-infrared-light irradiation for 5 min with an 800 nm laser at a low power density of ≈3.0 W cm(-2) . No bacterial activity is detected after 48 h postirradiation, which indicates that the heat generated from the irradiated plasmonic gold nanocrosses attached to bacteria is effective in eliminating and preventing the re-growth of the bacteria. Overall, the conjugated gold nanocrosses allow targeted and effective photothermal ablation of multidrug-resistant bacteria and their biofilms in the localized region with reduced nonspecific damage to normal tissue.

Metal nanostructures for non-enzymatic glucose sensing.

This review covers the recent development of metal nanostructures in electrochemical non-enzymatic glucose sensing. It highlights a variety of nanostructured materials including noble metals, other transition metals, bimetallic systems, and their hybrid with carbon-based nanomaterials. Particularly, attention is devoted to numerous approaches that have been implemented for improving the sensors performance by tailoring size, shape, composition, effective surface area, adsorption capability and electron-transfer properties. The correlation of the metal nanostructures to the glucose sensing performance is addressed with respect to the linear concentration range, sensitivity and detection limit. In overall, this review provides important clues from the recent scientific achievements of glucose sensor nanomaterials which will be essentially useful in designing better and more effective electrocatalysts for future electrochemical sensing industry.

Engineering polymeric microparticles as theranostic carriers for selective delivery and cancer therapy.

Multifunctional polymeric nano- and microparticles are engineered as theranostic carriers and their selective size-dependent cellular uptake is demonstrated. It is found that effective uptake and accumulation of nanoparticles occurs in both normal and cancer cells, whereas, that of microparticles occurs in cancer cells but not in normal cells, allowing cancer cells to be specifically targeted for local drug delivery.

Evaluation of Polymeric Nanoparticle Formulations by Effective Imaging and Quantitation of Cellular Uptake for Controlled Delivery of Doxorubicin

Various polymeric nanoparticles have been extensively engineered for applications in controlled drug release delivery in the last decades. Currently, there is a great demand to develop a strategy to qualitatively and quantitatively evaluate these polymeric nanoparticle formulations for producing innovative delivery systems. In this work, a screening platform is developed using luminescent quantum dots as drug model and imaging label to evaluate nanoparticle formulations incorporating either hydrophilic or hydrophobic drugs and imaging agents. It is validated that there is no influence of the incorporated entities on the cellular uptake profile. The use of quantum dots enables efficient detection and precise quantitation of cellular uptake of particles which occupy 25% of the cell volume. The correlation of quantum dot- and doxorubicin-incorporated nanoparticles is useful to develop an evaluation platform for nanoparticle formulations through imaging and quantitation. This platform is also used to observe the surface properties effect of other polymers such as chitosan and poly(ethylene) glycol on the cellular interaction and uptake. Moreover, quantum dots can be used to study microparticle theranostic delivery formulations by deliberately incorporating as visible ring surrounding the microparticles for their easy identifying and tracing in diagnostic and chemotherapeutic applications.

Microwave assisted synthesis of luminescent carbonaceous nanoparticles from silk fibroin for bioimaging

Bombyx mori silk as a natural protein based biopolymer with high nitrogen content, is abundant and sustainable because of its mass product all over the world per year. In this study, we developed a facile and fast microwave-assisted synthesis of luminescent carbonaceous nanoparticles using Bombyx mori silk fibroin and silk solution as the precursors. As a result, the obtained carbonaceous nanoparticles exhibit a photoluminescence quantum yield of ~20%, high stability, low cytotoxicity, high biocompatibility. Most importantly, we successfully demonstrated bioimaging using these luminescent carbonaceous nanoparticles with excitation dependent luminescence. In addition, the microwave-assisted hydrothermal method can be extended to convert other biomass into functional nanomaterials.