It is an active research field to develop fiber-shaped smart materials for biomedical applications. Here we report the development of the multifunctional core-shell hybrid microfibers with excellent mechanical and electrical performance as a new smart biomaterial. The microfibers were synthesized using a combination of co-axial spinning with a microfluidic device and subsequent dip-coating, containing a hydrogel core of bacterial cellulose (BC) and a conductive polymer shell layer of poly(3,4-ethylenedioxythiophene) (PEDOT). The hybrid microfibers were featured with a well-controlled microscopic morphology, exhibiting enhanced mechanic properties. A model drug, diclofenac sodium, can be loaded in the core layer of the microfibers in situ during the process of synthesis. Our experiments suggested that the releasing behaviors of the drug molecules from the microfibers were enhanced by external electrical stimulation. Interestingly, we demonstrated an excellent biocompatibility and electroactivity of the hybrid microfibers for PC12 cell culture, thus promising a flexible template for the reconstruction of electrically-responsive tissues mimicking muscle fibers or nerve networks.Statement of SignificanceFiber-shaped biomaterials are useful in creating various functional objects from one dimensional to three-dimensional. The fabrication of microfibers with integrated physicochemical properties and bio-performance has drawn an increasing attention on researchers from chemical to biomedical. This study combined biocompatible bacterial cellulose with electroconductive poly(3,4-ethylenedioxythiophene) and further reduced them to a highly electroactive BC/PEDOT core-shell microfiber electrode for electrochemical actuator design. The result showed that the microfibers were well fabricated and the release of drugs from the microfibers was enhanced and could be controlled under electrical stimulation externally. Considering the excellent biocompatibility and electroactive toward PC12 cells, these microfibers may find use as templates for the reconstruction of fiber-shaped functional tissues that mimic muscle fibers, blood vessels or nerve networks in vivo.Download high-res image (96KB)Download full-size image

The research field in enzyme-based biotechnology urgently requires the discovery of new materials and methods with high-performance. Here we report that highly crystalline graphite dots (GDs) can modulate enzyme activities, and simultaneously allow for real-time measurements on enzyme kinetics in combination with mass spectrometry (MS). A well-defined modulation of lipolytic activities from inhibition to enhancement can be realized by selectively coupling lipase enzymes with GDs containing specific functional groups on the surface. As a unique feature of our approach, GDs in the enzyme reaction can simultaneously serve as a versatile matrix for rapid and sensitive detection of the residual enzyme substrate, the intermediate or final product of lipolytic digestion using MS technology. Therefore, enzyme kinetic data can be collected in a real-time, high-throughput format. This work provides a new platform for enzymological research in hybrid bio-catalytic processes with advanced nanotechnology.

Radiotherapy is an important technology for the clinical treatment of cancer, but the patients suffer from the severe side effects after exposure to radiation. There is an urgent need to develop theranostic agents with excellent imaging capability and effective radiosensitization in order to minimize X-ray irradiation. Herein, we report an approach to synthesize peptide-templated Au nanoclusters (AuNCs) for theranostic radiosensitization. A new peptide (CCYKFR) is designed for the preparation of AuNCs with uniform size distribution and fluorescence (656 nm) of high photostability. CCYKFR–AuNCs feature highly efficient targeting/accumulation on mitochondria after endocytosis. With a series of experiments, we demonstrate that CCYKFR–AuNCs irradiated by 4 Gy X-rays can introduce a burst of mitoROS and severe DNA damage leading to cancer cell death. This study presents an important strategy to design theranostic nanomaterials with improved radiosensitization for the development of new anti-cancer therapies.

Currently there is a great need to design nano-carriers which enable multi-modal imaging of tumors and administration of therapeutics with high efficacy simultaneously. Herein we report a facile and robust approach to fabricate multifunctional nano-capsules based on double emulsions. The hybrid nano-capsules were loaded with BSA capped gold nanoclusters (AuNCs) and indocyanine green (ICG) for dual-modal imaging and effective photothermal therapy. RGD peptides were conjugated onto the surface of the hybrid nano-capsules to target cells overexpressing integrin ανβ3. We demonstrated that the as-prepared nano-capsules can be used for both one-photon and two-photon fluorescence imaging of tumor cells, and subsequent photothermal ablation with high effectiveness. The background noise of tissue autofluorescence was dramatically suppressed in the two-photon imaging mode. Therefore, it assisted a great deal to acquire images with a high signal-to-noise ratio using the hybrid nano-capsules. Due to a unique combination of the one-photon/two-photon fluorescence imaging and highly-effective photothermal properties, the hybrid nano-capsules may find broad biomedical applications as attractive theranostic nanomaterials.

There has been growing interest in utilizing highly photostable iridium(III) complexes as new luminescent probes for biotechnology and life science. Herein, iridium(III) complex with carboxyl group was synthesized and activated with N-hydroxysuccinimide, followed by tagging to the amino terminate of single-stranded DNA (ssDNA). The Ir-ssDNA probe was further combined with graphene oxide (GO) nanosheets to develop a GO-based biosensor for target ssDNA detection. The quenching efficiency of GO, and the photostability of iridium(III) complex and GO-Ir-ssDNA biosensor, were also investigated. On the basis of the high luminescence quenching efficiency of GO toward iridium(III) complex, the GO-Ir-ssDNA biosensor exhibited minimal background signals, while strong emission was observed when Ir-ssDNA desorbed from GO nanosheets and formed a double helix with the specific target, leading to a high signal-to-background ratio. Moreover, it was found that luminescent intensities of iridium(III) complex and GO-Ir-ssDNA biosensor were around 15 and 3 times higher than those of the traditional carboxyl fluorescein (FAM) dye and the GO-FAM-ssDNA biosensor after UV irradiation, respectively. Our study suggested the sensitive and selective Ir-ssDNA probe was suitable for the development of highly photostable GO-based detection platforms, showing promise for application beyond the OLED (organic light emitting diode) area.

Human mesenchymal stem cells (hMSCs) hold great promise for bone regeneration, yet the direction of MSC proliferation and induction of MSC differentiation remain challenging. Very recently, graphene provides a novel substrate for cell culture. Here, we report the utilization of mineralized three dimensional graphene (3DG) scaffolds for hMSC growth. The nano-structured hydroxyapatite (HA) particles decorated 3D graphene (HA-3DG) scaffolds were developed by mineralization in 10 times concentrated simulated body fluid (10SBF) containing 10 mM of HCO3−. The HA-3DG scaffolds showed higher roughness and cell proliferation compared with the 2D graphene films. More importantly, the mineralized 3DG scaffolds exhibited faster osteogenic commitment and stronger osteogenic differentiation (13.7, 10.9 and 1.89 fold at 7d, 10d and 14d respectively from the western blot analysis). These findings demonstrated the potential of mineralized 3DG scaffold as a promising platform for hMSC culture and bone regeneration.

The methodological development of nucleic acids detection is a rapidly growing research field. Here, we report a powerful method to detect nucleic acids by an integration of surface-enhanced Raman scattering and exonuclease III-assisted probe amplification. With a unique signal-on strategy, we have demonstrated that the target DNA of MnSOD gene in concentrations as low as 1 aM can reproducibly be detected, which offers a detection limit several orders of magnitude better than the previous reports in the literature. The new biosensor exhibits an excellent specificity in differentiating DNA sequences with a single-base mismatch. As a robust, flexible, and ultrasensitive approach, it promises important applications in clinical diagnostics and DNA identification where only a very limited amount of the biological sample is available.

Along with advances in life science and clinical research, there has been an increasing interest in enrichment technologies for proteins with post-translational modifications. Here we report a new platform to enrich and detect phosphopeptides using the hybrid nanofibers synthesized from bacterial cellulose (BC). Hydrothermal reactions have successfully been employed to synthesize BC@mTiO2 hybrid nanofibers. The morphology of the hybrid nanofibers has been characterized in detail. They are featured with tremendously increased specific surface areas and appropriate pore size for adsorption of phosphopeptides with high efficiency. The BC@mTiO2 tips allow improving both the sensitivity and selectivity of mass spectrometry by nearly two orders of magnitude compared with the commercial tips. As a robust and highly cost-effective platform, our approach has provided a nanotechnology invention to enrich and detect phosphorylated proteins with important biomedical applications.

Microbial infections continue to pose a serious threat to human health, thus calling attention to the development of new materials with better antibacterial applications. Here we report a microfluidic approach to fabricate core–shell GO-AgNPs/BC (graphene oxide–silver nanoparticles/bacterial cellulose) hydrogel microfibers with controlled-releasing and long-lasting antibacterial performance. Meters of the composite microfibers can be produced in 1 min by using a homemade microfluidic wet-spinning device. The as-prepared microfibers exhibit well-controlled morphological features at the nanoscale and excellent mechanical properties. We have demonstrated that the composite microfibers can effectively sterilize both Gram positive and negative bacterial strains, while remaining friendly to normal mammalian cells. This flexible approach of synthesizing core–shell composite microfibers promises important biomedical applications including materials science, tissue engineering, and regenerative medicine.Keywords: Antibacterial; Bacterial cellulose; Hydrogel Microfibers; Microfabrication; Sustainable;

It is currently a very active research area to develop new types of substrates which integrate various nanomaterials for surface-enhanced Raman scattering (SERS) techniques. Here we report a unique approach to prepare SERS substrates with reproducible performance. It features silicon mold-assisted magnetic assembling of superparamagnetic Fe3O4@Au nanoparticle clusters (NCs) into arrayed microstructures on a wafer scale. This approach enables the fabrication of both silicon-based and hydrogel-based substrates in a sequential manner. We have demonstrated that strong SERS signals can be harvested from these substrates due to an efficient coupling effect between Fe3O4@Au NCs, with enhancement factors >106. These substrates have been confirmed to provide reproducible SERS signals, with low variations in different locations or batches of samples. We investigate the spatial distributions of electromagnetic field enhancement around Fe3O4@Au NCs assemblies using finite-difference-time-domain (FDTD) simulations. The procedure to prepare the substrates is straightforward and fast. The silicon mold can be easily cleaned out and refilled with Fe3O4@Au NCs assisted by a magnet, therefore being re-useable for many cycles. Our approach has integrated microarray technologies and provided a platform for thousands of independently addressable SERS detection, in order to meet the requirements of a rapid, robust, and high throughput performance.

There is an increasing need to synthesize biocompatible nanofibers with excellent mechanical and electrical performance for electrochemical and biomedical applications. Here we report a facile approach to prepare electroactive and flexible 3D nanostructured biomaterials with high performance based on bacterial cellulose (BC) nanofibers. Our approach can coat BC nanofibers with poly(3,4-ethylenedioxythiophene) (PEDOT) by in situ interfacial polymerization in a controllable manner. The PEDOT coating thickness is adjustable by the monomer concentration or reaction time during polymerization, producing nanofibers with a total diameter ranging from 30 to 200 nm. This fabrication process also provides a convenient method to tune different parameters such as the average pore size and electrical conductivity on the demands of actual applications. Our experiments have demonstrated that the 3D BC/PEDOT nanofibers exhibit high specific surface area, excellent mechanical properties, electroactive stability, and low cell cytotoxicity. With electrical stimulation, calcium imaging of PC12 neural cells on BC/PEDOT nanofibers has revealed a significant increase in the percentage of cells with higher action potentials, suggesting an enhanced capacitance effect of charge injection. As an attractive solution to the challenge of designing better electrode-cell interfaces, 3D BC/PEDOT nanofibers promise many important applications such as biosensing devices, smart drug delivery systems, and implantable electrodes for tissue engineering.Keywords: bacterial cellulose; biocompatible; electroactive; electrode-cell interface; three-dimensional nanofibers

There is a great need for functional polymers in various applications. This study aims to develop a well-defined brush-type copolymer P(PEGMA-N3-co-PEGMEMA)-b-PMAA via the technique of atom transfer radical polymerization (ATRP), and further to demonstrate a plurality of plug-and-play functions of this copolymer.

Advanced neural research demands new electrode materials with high performance. Herein, we have developed a facile approach to synthesize amphiphilic reduced graphene oxide (rGO) and demonstrated its performance in electrically stimulating neural cells with high charge injection capacity. Synthesis of the amphiphilic rGO features covalent functionalization and simultaneous thermal reduction in a one-step manner. The covalent functionalization of methoxy poly(ethylene glycol) (mPEG) chains on the rGO surface not only provides a high dispersibility in various solvents, enabling convenient post-treatment processes, but also allows for an enhancement in double-layer charging capacitance. Calcium imaging of PC12 neural cells on the amphiphilic mPEG–rGO films has revealed a predominant increase in the percentage of cells with higher action potentials, derived from double-layer capacitance enhancement in charge injection. These results suggest that the new amphiphilic mPEG–rGO material is capable of providing a much safer and efficacious solution for neural prostheses applications.

A facile approach was developed to fabricate patterned substrates of nano-graphene oxide, demonstrating highly localized and efficient gene delivery to multiple cell lines in a substrate-mediated manner. The GO substrates served as a valid platform to preconcentrate PEI/pDNA complexes and maintain their gradual releasing for a relatively long period of time. Our approach allowed successful gene delivery in selected groups of cells on the stripe-patterned GO substrates, without transfecting their neighbor cells directly cultured on glass. These GO substrates exhibited excellent biocompatibility and enabled effective gene transfection for various cell lines including stem cells, thus promising important applications in stem cell research and tissue engineering.Keywords: localized gene delivery; nano-graphene oxide; nano−bio interface; patterned substrates;

There is a great need to develop multifunctional nanoparticles (MFNPs) for cancer biomarker-based detection and highly selective therapeutic treatment simultaneously. Here we describe a facile approach of layer-by-layer-assembled MFNPs conjugated with monoclonal antibody anti-HER2, demonstrating the specific detection of breast cancer BT474 cells (biomarker HER2 positive) with a high signal-to-noise ratio. The MFNPs contain a well-defined core–shell structure of UCNP@Fe3O4@Au coated by poly(ethylene glycol) (PEG) and anti-HER2 antibody, displaying excellent dispersity in various aqueous solutions. This unique combination of nanoparticles and ligand molecules allows us to perform photothermal treatment (PTT) of the cancer cells, while simultaneously quantifying the distribution of MFNPs on a cancer cell surface induced by antigen–antibody binding events. An important finding is that cancer cells adjacent to each other or in physical proximity within micrometers may end up with different fates of survival or death in PTT. This dramatic difference is determined by the antigen–antibody binding events at the interface of MFNPs and cells because of tumor cell heterogeneity. Therefore, our experiments reveal a new scale of the highly localized feature of the photothermal effect at the single−cell level illuminated by a continuous−wave near−IR laser.Keywords: detection of cancer cells; multifunctional nanoparticles; nano−bio interface; photothermal treatment; tumor heterogeneity;

Currently there is a great need to design nano-carriers which enable multi-modal imaging of tumors and administration of therapeutics with high efficacy simultaneously. Herein we report a facile and robust approach to fabricate multifunctional nano-capsules based on double emulsions. The hybrid nano-capsules were loaded with BSA capped gold nanoclusters (AuNCs) and indocyanine green (ICG) for dual-modal imaging and effective photothermal therapy. RGD peptides were conjugated onto the surface of the hybrid nano-capsules to target cells overexpressing integrin ανβ3. We demonstrated that the as-prepared nano-capsules can be used for both one-photon and two-photon fluorescence imaging of tumor cells, and subsequent photothermal ablation with high effectiveness. The background noise of tissue autofluorescence was dramatically suppressed in the two-photon imaging mode. Therefore, it assisted a great deal to acquire images with a high signal-to-noise ratio using the hybrid nano-capsules. Due to a unique combination of the one-photon/two-photon fluorescence imaging and highly-effective photothermal properties, the hybrid nano-capsules may find broad biomedical applications as attractive theranostic nanomaterials.

Advanced neural research demands new electrode materials with high performance. Herein, we have developed a facile approach to synthesize amphiphilic reduced graphene oxide (rGO) and demonstrated its performance in electrically stimulating neural cells with high charge injection capacity. Synthesis of the amphiphilic rGO features covalent functionalization and simultaneous thermal reduction in a one-step manner. The covalent functionalization of methoxy poly(ethylene glycol) (mPEG) chains on the rGO surface not only provides a high dispersibility in various solvents, enabling convenient post-treatment processes, but also allows for an enhancement in double-layer charging capacitance. Calcium imaging of PC12 neural cells on the amphiphilic mPEG–rGO films has revealed a predominant increase in the percentage of cells with higher action potentials, derived from double-layer capacitance enhancement in charge injection. These results suggest that the new amphiphilic mPEG–rGO material is capable of providing a much safer and efficacious solution for neural prostheses applications.

Radiotherapy is an important technology for the clinical treatment of cancer, but the patients suffer from the severe side effects after exposure to radiation. There is an urgent need to develop theranostic agents with excellent imaging capability and effective radiosensitization in order to minimize X-ray irradiation. Herein, we report an approach to synthesize peptide-templated Au nanoclusters (AuNCs) for theranostic radiosensitization. A new peptide (CCYKFR) is designed for the preparation of AuNCs with uniform size distribution and fluorescence (656 nm) of high photostability. CCYKFR–AuNCs feature highly efficient targeting/accumulation on mitochondria after endocytosis. With a series of experiments, we demonstrate that CCYKFR–AuNCs irradiated by 4 Gy X-rays can introduce a burst of mitoROS and severe DNA damage leading to cancer cell death. This study presents an important strategy to design theranostic nanomaterials with improved radiosensitization for the development of new anti-cancer therapies.