Chenbo Dong

Preparation of highly photoluminescent sulfur-doped carbon dots for Fe(III) detection

Sulfur-doped carbon dots (S-doped C-dots)were synthesized using a simple and straightforward hydrothermal method. The as-prepared S-doped C-dots exhibit significant fluorescence quantum yield (67%) and unique emission behavior. The spherical S-doped C-dots have an average diameter of 4.6 nm and the fluorescence of S-doped C-dots can be effectively and selectively quenched by Fe3+ ions. Thus, S-doped C-dots were applied as probes toward Fe3+ detection, exhibiting a limit of detection of 0.1 μM.

Self-Assembling Peptide Nanofibrous Hydrogel as a Versatile Drug Delivery Platform

Molecular hydrogels have been widely explored in various biomedical applications, such as cell culture, tissue engineering and drug delivery. Peptide-based hydrogel nanoparticles represent a promising alternative to current drug delivery approaches and cell carriers for tissue engineering, due to their encapsulation stability, water solubility and biocompatibility. This review focuses on recent advances in the use of self-assembling peptide nanogels for applications in drug delivery. We firstly introduce a self-assembly mechanism for small molecules used in the peptide hydrogel, and then describe recent methods for controlling the assembly of molecular hydrogelations. A particular emphasis is placed on recent advances in the use of different types of peptide hydrogels as drug delivery carriers. Lastly, the current challenges and future perspectives for self-assembling peptide hydrogels in drug delivery applications are discussed.

Synthesis, mechanistic investigation, and application of photoluminescent sulfur and nitrogen co-doped carbon dots

Heteroatom doped carbon dots (CDs) with consummate photoluminescence quantum yield (PLQY) are of great interest in various applications such as trace element detection, biomolecule markers, and chemical sensing. However, due to the low doping efficiency of the reaction, a high precursor ratio is routinely used to obtain CDs with considerable photoluminescence quantum yield (PLQY). In this contribution, we report a single-step hydrothermal method having the highest doping efficiency to synthesize sulfur and nitrogen co-doped semi-crystalline carbon dots (S,N-CDs) with superior quantum yield (QY). Here, the unprecedented doping efficiency of the reaction enables an order of magnitude reduction in the starting precursor ratio, in comparison with previous reports. Moreover, for the first time, complementary theoretical and comprehensive spectroscopic techniques were employed to derive deep insight into the photoluminescence mechanism and the shifting of specific energy levels in doped CDs was identified as the reason behind the enhanced photoluminescence of doped CDs. The PLQY and luminescent characteristics of the S,N-CDs can be tuned by controlling the precursor molar ratio, the extent of surface oxidation, and chemical status of S in the CDs. While most methods report high PLQY for amorphous CDs, our technique produces semi-crystalline CDs with more than 55% QY. Another unique attribute of the S,N-CDs is the high monodispersity and defined surface chemistry and the resultant highly robust excitation-independent luminescence that is stable over a broad range of pH values and in an extremely reactive environment. The detailed structural and chemical investigations using spectroscopic and microscopic techniques combining molecular simulation revealed that the superior PLQY and luminescence of S,N-CDs are due to the heteroatom directed, oxidized carbon-based surface passivation. The remarkable, robust fluorescence properties of S,N-CDs were applied for the ultra-trace detection of Hg2+ with a detection limit of 100 pM. The novel insights into the photoluminescence of doped CDs, the robust luminescence, and enhanced doping reaction efficiency reported here are envisaged to drive transformative changes in the design of CDs with peerless properties for futuristic applications.

Effect of Fiber Length on Carbon Nanotube-Induced Fibrogenesis

Given their extremely small size and light weight, carbon nanotubes (CNTs) can be readily inhaled by human lungs resulting in increased rates of pulmonary disorders, particularly fibrosis. Although the fibrogenic potential of CNTs is well established, there is a lack of consensus regarding the contribution of physicochemical attributes of CNTs on the underlying fibrotic outcome. We designed an experimentally validated in vitro fibroblast culture model aimed at investigating the effect of fiber length on single-walled CNT (SWCNT)-induced pulmonary fibrosis. The fibrogenic response to short and long SWCNTs was assessed via oxidative stress generation, collagen expression and transforming growth factor-beta (TGF-β) production as potential fibrosis biomarkers. Long SWCNTs were significantly more potent than short SWCNTs in terms of reactive oxygen species (ROS) response, collagen production and TGF-β release. Furthermore, our finding on the length-dependent in vitro fibrogenic response was validated by the in vivo lung fibrosis outcome, thus supporting the predictive value of the in vitro model. Our results also demonstrated the key role of ROS in SWCNT-induced collagen expression and TGF-β activation, indicating the potential mechanisms of length-dependent SWCNT-induced fibrosis. Together, our study provides new evidence for the role of fiber length in SWCNT-induced lung fibrosis and offers a rapid cell-based assay for fibrogenicity testing of nanomaterials with the ability to predict pulmonary fibrogenic response in vivo.

Enzyme Catalytic Efficiency: A Function of Bio–Nano Interface Reactions

Biocatalyst immobilization onto carbon-based nanosupports has been implemented in a variety of applications ranging from biosensing to biotransformation and from decontamination to energy storage. However, retaining enzyme functionality at carbon-based nanosupports was challenged by the non-specific attachment of the enzyme as well as by the enzyme-enzyme interactions at this interface shown to lead to loss of enzyme activity. Herein, we present a systematic study of the interplay reactions that take place upon immobilization of three pure enzymes namely soybean peroxidase, chloroperoxidase, and glucose oxidase at carbon-based nanosupport interfaces. The immobilization conditions involved both single and multipoint single-type enzyme attachment onto single and multi-walled carbon nanotubes and graphene oxide nanomaterials with properties determined by Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray analysis (EDX), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Our analysis showed that the different surface properties of the enzymes as determined by their molecular mapping and size work synergistically with the carbon-based nanosupports physico-chemical properties (i.e., surface chemistry, charge and aspect ratios) to influence enzyme catalytic behavior and activity at nanointerfaces. Knowledge gained from these studies can be used to optimize enzyme-nanosupport symbiotic reactions to provide robust enzyme-based systems with optimum functionality to be used for fermentation, biosensors, or biofuel applications.

Rejuvenation of chondrogenic potential in a young stem cell microenvironment

Autologous cells suffer from limited cell number and senescence during ex vivo expansion for cartilage repair. Here we found that expansion on extracellular matrix (ECM) deposited by fetal synovium-derived stem cells (SDSCs) (FE) was superior to ECM deposited by adult SDSCs (AE) in promoting cell proliferation and chondrogenic potential. Unique proteins in FE might be responsible for the rejuvenation effect of FE while advantageous proteins in AE might contribute to differentiation more than to proliferation. Compared to AE, the lower elasticity of FE yielded expanded adult SDSCs with lower elasticity which could be responsible for the enhancement of chondrogenic and adipogenic differentiation. MAPK and noncanonical Wnt signals were actively involved in ECM-mediated adult SDSC rejuvenation.

Graphene and graphene oxide: advanced membranes for gas separation and water purification

Advanced membrane systems with excellent permeance are important for controllable separation processes, such as gas separation and water purification. The ideal candidate materials should be very thin to provide high permeance, be stiff enough to withstand working under high applied pressure, with a large surface area and micro- or nano-pore structure for excellent selectivity. Graphene oxide (GO) nanosheets are graphene with oxygen-containing functional groups, obtained by treating graphite with strong oxidizers. Graphene-based materials, by virtue of their high mechanical strength, large surface area, single-atom-thick unique two-dimensional honeycomb lattice structure, and narrow pore distribution, provide exciting opportunities to assemble novel types of advanced, ultra-thin, high-efficiency membrane devices. In this contribution, we discuss the progress made in the direction of using graphene oxide as high-efficiency membranes for gas separation and water purification. The primary focus will be on introducing the fabrication processes, exceptional properties, and innovative membrane applications of two-dimensional graphene oxide materials for controllable separation processes. This state-of-the-art review will provide a platform for understanding the intricate details of gas and water molecular transport through laminar graphene oxide membranes, as well as a summary of the latest process in the field.

Crosslink density of a biomimetic poly(HEMA)-based hydrogel influences growth and proliferation of attachment dependent RMS 13 cells

The mechanical properties of biomaterials have profound consequences on cellular and host responses, however, the underlying mechanisms remain poorly understood. Presented are findings that confirm a clear relationship between the elastic modulus, the bulk-to-bound water ratio and the adaptive attachment of attachment dependent cells. We show that biomimetic hydrogels possessing no specific integrin binding motifs but that are of lower elastic modulus and lower bulk-to-bound water ratio, preferentially support cell attachment. Anchorage-dependent human muscle fibroblasts (RMS 13) were cultured on tetraethylene glycol (TEGDA) cross-linked poly(2-hydroxyethyl methacrylate) [poly(HEMA)]-based biomimetic hydrogels containing phosphorylcholine (PC) (1 mol%) and dimethylamino amino ethyl methacrylate (DMAEMA), a 3° amine (5 mol%), as well as on silicone and agarose controls. Changes in the cross-link density (1 to 12 mol%) of the hydrogel produced a monotonic reduction in the glass transition temperature, Tg (131.8 °C at 1 mol% TEGDA to 110.4 °C at 12 mol% TEGDA), but an exponential increase in the bulk-to-bound water (4.25 at 1 mol% to 27.04 at 12 mol%) that exactly parallels the increase in elastic modulus as measured by nano-indentation AFM (152 ± 62 kPa at 1 mol% TEGDA to 1777 ± 1152 kPa at 12 mol% TEGDA). Enumeration, MTT assay and fluorescence microscopy following 4, 8 and 12 days of culture confirms that short-term cell viability and long term proliferation were favored on low cross-link density, low modulus hydrogels and that cells were preferentially attached to low cross-link density hydrogels. Bound water is central to the adaptive attachment of attachment dependent cells.

The effect of the physicochemical properties of bioactive electroconductive hydrogels on the growth and proliferation of attachment dependent cells

The physicochemical properties of soft electrode materials for the abio-bio interface of advanced biosensors and next generation bionic devices in the form of electroconductive hydrogels (ECH) of interpenetrating networks of polypyrrole formed within poly(hydroxyethylmethacrylate)-based hydrogels were examined. The 1.5 mol% UV-crosslinked tetraethyleneglycol diacrylate (TEGDA) (step 1) poly(HEMA) and the electropolymerized (step 2) polypyrrole co-networks were covalently joined by the inclusion of a bifunctional monomer (1.5 mol%), 2-methacryloyloxyethyl-4(3-pyrrolyl)butanate (MPB) that served to covalently link the two networks. The optical absorbance, degree of hydration, the frequency dependent electrical impedance and the elastic modulus were examined as a function of electropolymerization charge density (step 2) (1-900 mC/cm(2)) used to prepare the linked, interpenetrating co-networks. The absorption at 430 nm showed a monotonic increase with electropolymerization charge density and correlated with the increase in elastic modulus [56 (± 32)-499 (± 293) kPa], the decrease in % hydration (68-0%) and the decrease in membrane electrical resistance. Polypyrrole (PPy) grows initially from the gel-electrode interface to fill voids within the hydrogel and ultimately onto the surface of the hydrogel. Growth of attachment dependent Rhabdomyosarcoma (RMS13) and pheochromocytoma (PC 12) cells reflects this evolution, showing an increase to a maximal value and then to decrease again at high electropolymerization charge density.

Highly fluorescent Zn-doped carbon dots as Fenton reaction-based bio-sensors: an integrative experimental–theoretical consideration

Heteroatom doped carbon dots (CDs), with high photoluminescence quantum yield (PLQY), are of keen interest in various applications such as chemical sensors, bio-imaging, electronics, and photovoltaics. Zinc, an important element assisting the electron-transfer process and an essential trace element for cells, is a promising metal dopant for CDs, which could potentially lead to multifunctional CDs. In this contribution, we report a single-step, high efficiency, hydrothermal method to synthesize Zn-doped carbon dots (Zn-CDs) with a superior PLQY. The PLQY and luminescence characteristic of Zn-CDs can be tuned by controlling the precursor ratio, and the surface oxidation in the CDs. Though a few studies have reported metal doped CDs with good PLQY, the as prepared Zn-Cds in the present method exhibited a PLQY up to 32.3%. To the best of our knowledge, there is no report regarding the facile preparation of single metal-doped CDs with a QY more than 30%. Another unique attribute of the Zn-CDs is the high monodispersity and the resultant highly robust excitation-independent luminescence that is stable over a broad range of pH values. Spectroscopic investigations indicated that the superior PLQY and luminescence of Zn-CDs are due to the heteroatom directed, oxidized carbon-based surface passivation. Furthermore, we developed a novel and sensitive biosensor for the detection of hydrogen peroxide and glucose leveraging the robust fluorescence properties of Zn-CDs. Under optimal conditions, Zn-CDs demonstrated high sensitivity and response to hydrogen peroxide and glucose over a wide range of concentrations, with a linear range of 10-80 μM and 5-100 μM, respectively, indicating their great potential as a fluorescent probe for chemical sensing.