Spontaneous Cross-linking Research Articles

Mangostanin hyaluronic acid hydrogel as an effective biocompatible alternative to chlorhexidine

Periodontal disease (PD) prevention and treatment products typically demonstrate excellent antibacterial activity, but recent studies have raised concerns about their toxicity on oral tissues. Therefore, finding a biocompatible alternative that retains antimicrobial properties is imperative. In this study, a chemically modified hyaluronic acid (HA) hydrogel containing mangostanin (MGTN) was developed. Native HA was chemically modified, incorporating amino and aldehyde groups in different batches of HA, allowing spontaneous crosslinking and gelation when combined at room temperature. MGTN at different concentrations was incorporated before gelation. The structure, swelling characteristics MGTN release, rheological parameters, and in vitro degradation performance of the loaded hydrogel were first evaluated in the study. Then, antimicrobial properties were tested on Porphyromonas gingivalis and its biocompatibility in 3D-engineered human gingiva. HA hydrogel was very stable and showed a sustained release for MGTN for at least 7 days. MGTN-loaded HA hydrogel showed equivalent antimicrobial activity compared to a commercial gel of HA containing 0.2 % chlorhexidine (CHX). In contrast, while MGTN HA hydrogel was biocompatible, CHX gel showed high cytotoxicity, causing cell death and tissue damage. Modified HA hydrogel allows controlled release of MGTN, resulting in a highly biocompatible hydrogel with antibacterial properties. This hydrogel is a suitable alternative therapy to prevent and treat PD.

A Conserved Intramolecular Ion-Pair Plays a Critical but Divergent Role in Regulation of Dimerization and Transport Function among the Monoamine Transporters.

The monoamine transporters, including the serotonin transporter (SERT), dopamine transporter (DAT), and norepinephrine transporter (NET), are the therapeutic targets for the treatment of many neuropsychiatric disorders. Despite significant progress in characterizing the structures and transport mechanisms of these transporters, the regulation of their transport functions through dimerization or oligomerization remains to be understood. In the present study, we identified a conserved intramolecular ion-pair at the third extracellular loop (EL3) connecting TM5 and TM6 that plays a critical but divergent role in the modulation of dimerization and transport functions among the monoamine transporters. The disruption of the ion-pair interactions by mutations induced a significant spontaneous cross-linking of a cysteine mutant of SERT and an increase in cell surface expression but with an impaired specific transport activity. On the other hand, similar mutations of the corresponding ion-pair residues in both DAT and NET resulted in an opposite effect on their oxidation-induced dimerization, cell surface expression, and transport function. Reversible biotinylation experiments indicated that the ion-pair mutations slowed down the internalization of SERT but stimulated the internalization of DAT. In addition, cysteine accessibility measurements for monitoring SERT conformational changes indicated that substitution of the ion-pair residues resulted in profound effects on the rate constants for cysteine modification in both the extracellular and cytoplasmatic substrate permeation pathways. Furthermore, molecular dynamics simulations showed that the ion-pair mutations increased the interfacial interactions in a SERT dimer but decreased it in a DAT dimer. Taken together, we propose that the transport function is modulated by the equilibrium between monomers and dimers on the cell surface, which is regulated by a potential compensatory mechanism but with different molecular solutions among the monoamine transporters. The present study provided new insights into the structural elements regulating the transport function of the monoamine transporters through their dimerization.

In-Situ Polymer Framework Strategy Enabling Printable and Efficient Perovskite Solar Cells by Mitigating "Coffee Ring" Effect.

Organic-inorganic hybrid perovskites are considered ideal candidates for future photovoltaic applications due to their excellent photovoltaic properties. Although solution-printed manufacturing has shown inherent potential for the low-cost, high-throughput production of thin-film semiconductor electronics, the high-quality and high-reproducibility deposition of large-area perovskite remains a bottleneck that restricts their commercialization due to the droplet coffee-ring effect (CRE). In this study, these issues are addressed by introducing an in situ polymer framework. The 3D framework formed by spontaneous cross-linking improves the precursor viscosity and homogenizes its heat diffusion coefficient, counteracting the lateral capillary flow of the colloidal particles and anchoring their flocculent movement. Thus, the Marangoni convection intensity is properly controlled to ensure high-quality perovskite films, which significantly enhances reproducibility in printing efficient photovoltaics by mitigating the CRE. Subsequently, the perovskite solar cells and modules achieve power conversion efficiencies of 23.94 and 17.53%, and exhibit positive environmental stability, retaining over 90 and 78% efficiency after storage for 2500 and 1600h, respectively. This work may serves as a foundation for exploring precursor rheology to match the homogeneous deposition requirements of perovskite photovoltaics and facilitating the advancement of their printing manufacturing and commercialization transition.

Efficient and stable CO2 capture using a scalable and spontaneous cross-linking amine-functionalized nano-Al2O3 adsorbent

The spontaneous cross-linking between polyethyleneimine and nano-Al2O3 facilitates efficient and stable CO2 capture.

Yeast Display Enables Identification of Covalent Single-Domain Antibodies against Botulinum Neurotoxin Light Chain A.

While covalent drug discovery is reemerging as an important route to small-molecule therapeutic leads, strategies for the discovery and engineering of protein-based irreversible binding agents remain limited. Here, we describe the use of yeast display in combination with noncanonical amino acids (ncAAs) to identify irreversible variants of single-domain antibodies (sdAbs), also called VHHs and nanobodies, targeting botulinum neurotoxin light chain A (LC/A). Starting from a series of previously described, structurally characterized sdAbs, we evaluated the properties of antibodies substituted with reactive ncAAs capable of forming covalent bonds with nearby groups after UV irradiation (when using 4-azido-l-phenylalanine) or spontaneously (when using O-(2-bromoethyl)-l-tyrosine). Systematic evaluations in yeast display format of more than 40 ncAA-substituted variants revealed numerous clones that retain binding function while gaining either UV-mediated or spontaneous crosslinking capabilities. Solution-based analyses indicate that ncAA-substituted clones exhibit site-dependent target specificity and crosslinking capabilities uniquely conferred by ncAAs. Interestingly, not all ncAA substitution sites resulted in crosslinking events, and our data showed no apparent correlation between detected crosslinking levels and distances between sdAbs and LC/A residues. Our findings highlight the power of yeast display in combination with genetic code expansion in the discovery of binding agents that covalently engage their targets. This platform streamlines the discovery and characterization of antibodies with therapeutically relevant properties that cannot be accessed in the conventional genetic code.

Model of abasic site DNA cross-link repair; from the architecture of NEIL3 DNA binding domains to the X-structure model.

Covalent DNA interstrand crosslinks are toxic DNA damage lesions that block the replication machinery that can cause a genomic instability. Ubiquitous abasic DNA sites are particularly susceptible to spontaneous cross-linking with a base from the opposite DNA strand. Detection of a crosslink induces the DNA helicase ubiquitination that recruits NEIL3, a DNA glycosylase responsible for the lesion removal. NEIL3 utilizes several zinc finger domains indispensable for its catalytic NEI domain repairing activity. They recruit NEIL3 to the repair site and bind the single-stranded DNA. However, the molecular mechanism underlying their roles in the repair process is unknown. Here, we report the structure of the tandem zinc-finger GRF domain of NEIL3 and reveal the molecular details of its interaction with DNA. Our biochemical data indicate the preferential binding of the GRF domain to the replication fork. In addition, we obtained a structure for the catalytic NEI domain in complex with the DNA reaction intermediate that allowed us to construct and validate a model for the interplay between the NEI and GRF domains in the recognition of an interstrand cross-link. Our results suggest a mechanism for recognition of the DNA replication X-structure by NEIL3, a key step in the interstrand cross-link repair.

Oxi-HA/ADH Hydrogels: A Novel Approach in Tissue Engineering and Regenerative Medicine

Hyaluronic acid (HA) is a natural polyelectrolyte abundant in mammalian connective tissues, such as cartilage and skin. Both endogenous and exogenous HA produced by fermentation have similar physicochemical, rheological, and biological properties, leading to medical and dermo-cosmetic products. Chemical modifications such as cross-linking or conjugation in target groups of the HA molecule improve its properties and in vivo stability, expanding its applications. Currently, HA-based scaffolds and matrices are of great interest in tissue engineering and regenerative medicine. However, the partial oxidation of the proximal hydroxyl groups in HA to electrophilic aldehydes mediated by periodate is still rarely investigated. The introduced aldehyde groups in the HA backbone allow spontaneous cross-linking with adipic dihydrazide (ADH), thermosensitivity, and noncytotoxicity to the hydrogels, which are advantageous for medical applications. This review provides an overview of the physicochemical properties of HA and its usual chemical modifications to better understand oxi-HA/ADH hydrogels, their functional properties modulated by the oxidation degree and ADH concentration, and the current clinical research. Finally, it discusses the development of biomaterials based on oxi-HA/ADH as a novel approach in tissue engineering and regenerative medicine.

Hierarchical Porous Polymers via a Microgel Intermediate: Green Synthesis and Applications toward the Removal of Pollutants

Exploring a synthetic approach to prepare processable hierarchical porous polymers (PPs) is challenging. In the article, a strategic approach is presented, where polymerization (hyperbranching)-induced self-assembly in water leads to the formation of porous microgels (containing both micropores and mesopores), which is followed by spontaneous cross-linking of those intermediate microgels, leading to the formation of PPs. The synthetic process involves simple and green reactions. During this process, hydrophobicity of chosen monomers controls the morphology and porosity of the microgel, which in turn dictates the hierarchical porous morphology of the PPs. Such a synthetic hierarchy during the PP formation in water ensures increase of both surface area and active functionalities among different prototypes. Furthermore, under right conditions, the microgel-based emulsion can be used to form homogeneous porous thin films (average thickness 2–10 nm), which is important in the context of processability of such polymers. The synthesized hierarchical PPs have excellent adsorption capacities for different pollutants, such as iodine (3020 mg/g), methyl orange (1571 mg/g), congo red (1125 mg/g), and high CO2 uptake capacity with good selectivity.

Synthesis of precision antibody conjugates using proximity-induced chemistry.

Rationale: Therapeutic antibody conjugates allow for the specific delivery of cytotoxic agents or immune cells to tumors, thus enhancing the antitumor activity of these agents and minimizing adverse systemic effects. Most current antibody conjugates are prepared by nonspecific modification of antibody cysteine or lysine residues, inevitably resulting in the generation of heterogeneous conjugates with limited therapeutic efficacies. Traditional strategies to prepare homogeneous antibody conjugates require antibody engineering or chemical/enzymatic treatments, processes that often affect antibody folding and stability, as well as yield and cost. Developing a simple and cost-effective way to precisely couple functional payloads to native antibodies is of great importance.Methods: We describe a simple proximity-induced antibody conjugation method (pClick) that enables the synthesis of homogeneous antibody conjugates from native antibodies without requiring additional antibody engineering or post-synthesis treatments. A proximity-activated crosslinker is introduced into a chemically synthesized affinity peptide modified with a bioorthogonal handle. Upon binding to a specific antibody site, the affinity peptide covalently attaches to the antibody via spontaneous crosslinking, yielding an antibody molecule ready for bioorthogonal conjugation with payloads.Results: We have prepared well-defined antibody-drug conjugates and bispecific small molecule-antibody conjugates using pClick technology. The resulting conjugates exhibit excellent in vitro cytotoxic activity against cancer cells and, in the case of bispecific conjugates, superb antitumor activity in mouse xenograft models.Conclusions: Our pClick technology enables efficient, simple, and site-specific conjugation of various moieties to the existing native antibodies. This technology does not require antibody engineering or additional UV/chemical/enzymatic treatments, therefore providing a general, convenient strategy for developing novel antibody conjugates.

Synthesis of Precision Antibody Conjugates Using Proximity-Induced Chemistry

To produce homogeneous antibody conjugates, antibody engineering or chemical/enzymatic treatments are required, processes that often affect antibody folding and stability, as well as yield and cost. Here, we describe a simple proximity-induced antibody conjugation method (pClick) that enables the synthesis of homogeneous antibody conjugates from native antibodies without requiring additional antibody engineering or post-synthesis treatment. A proximity-activated crosslinker is introduced into a chemically synthesized affinity peptide modified with a bioorthogonal handle. Upon binding to a specific antibody site, the affinity peptide covalently attaches to the antibody via spontaneous crosslinking, yielding an antibody molecule ready for bioorthogonal conjugation with payloads. We have prepared well-defined antibody-drug conjugates and bispecific small molecule-antibody conjugates, exhibiting excellent in vitro cytotoxic activity against cancer cells and superb antitumor activity in mouse xenograft models. This technology does not require antibody engineering or additional UV/chemical/enzymatic treatments, therefore providing a general, convenient strategy for developing novel antibody conjugates.

Facile two-step phosphazine-based network coating for flame retardant cotton

There is a need for durable flame retardant treatments for cotton fabric in order to reduce the risk associated with fires. Many current industrial treatments make use of toxic halogenated organic flame retardants or utilize formaldehyde-evolving chemistry. A facile two-step process is described to coat cotton fabric based on a spontaneous crosslinking reaction between branched polyethyleneimine (PEI) and hexachlorocyclotriphosphazene (HCCP). A coating produced from solutions of 10 wt% PEI and 5 wt% HCCP endows the cotton fabric with a high limiting oxygen index (33.8%), self-extinguishing behavior in open flame testing, and an 85% reduction in peak heat release rate. This treated fabric also maintains self-extinguishing behavior after a simulated washing test. This unique combination of properties is the result of a strongly networked coating that intumesces during burning. The simplicity of this treatment and its formaldehyde-free chemistry make it a good option for replacing organo-halogen and formaldehyde-evolving treatments.

Microfluidic Formation of Hydrogel Microcapsules with a Single Aqueous Core by Spontaneous Cross-Linking in Aqueous Two-Phase System Droplets.

We report a simple process to fabricate monodisperse tetra-arm poly(ethylene glycol) (tetra-PEG) hydrogel microcapsules with an aqueous core and a semipermeable hydrogel shell through the formation of aqueous two-phase system (ATPS) droplets consisting of a dextran-rich core and a tetra-PEG macromonomer-rich shell, followed by a spontaneous cross-end coupling reaction of tetra-PEG macromonomers in the shell. Different from conventional techniques, this process enables for the continuous production of hydrogel microcapsules from water-in-oil emulsion droplets under mild conditions in the absence of radical initiators and external stimuli such as heating and ultraviolet light irradiation. We find that rapid cross-end coupling reaction of tetra-PEG macromonomers in ATPS droplets in the range of pH from 7.4 to 7.8 gives hydrogel microcapsules with a kinetically arrested core-shell structure. The diameter and core-shell ratio of the microcapsules can be easily controlled by adjusting flow rates and ATPS compositions. On the other hand, the slow cross-end coupling reaction of tetra-PEG macromonomers in ATPS droplets at pH 7.0 and lower induces structural change from core-shell to Janus during the reaction, which eventually forms hydrogel microparticles with a thermodynamically stable crescent structure. We believe that these hydrogel microparticles with controlled structures can be used in biomedical fields such as cell encapsulation, biosensors, and drug delivery carriers for sensitive biomolecules.

Spontaneous cross-linking of proteins at aspartate and asparagine residues is mediated via a succinimide intermediate.

The breakdown of long-lived proteins (LLPs) is associated with aging, as well as disease; however, our understanding of the molecular processes involved is still limited. Of particular relevance, cross-linked proteins are often reported in aged tissues but the mechanisms for their formation are poorly understood. In the present study, sites of protein cross-linking in human ocular lenses were characterized using proteomic techniques. In long-lived lens proteins, several sites of cross-linking were found to involve the addition of Lys to Asp or Asn residues. Using model peptides containing Asp or Asn, a mechanism was elucidated that involves a succinimide intermediate. Succinimides formed readily from Asn at neutral pH, whereas a higher rate of formation from Asp peptides was observed at more acidic pHs. Succinimides were found to be relatively stable in the absence of nucleophiles. Since racemization of Asp residues, as well as deamidation of Asn, involves a succinimide intermediate, sites of d-Asp and isoAsp in LLPs should also be considered as potential sites of protein covalent cross-linking.

Simple and efficient fabrication of pomegranate-like Fe2O3@C on carbon cloth as an anode for lithium-ion batteries

Pomegranate-like Fe2O3@C nanoparticles on carbon cloth (CC) as an anode for lithium-ion batteries are synthesized via a combination of dip-coating and hydrothermal synthesis. The spontaneous crosslinking reaction between sodium alginate (SA) and Fe3+ first creates a chelate compound, and then the SA-Fe3+ chelate is converted to Fe2O3@C nanoparticles after a simple hydrothermal treatment. The Fe2O3@C nanoparticles exhibit pomegranate-like morphology with an average diameter of 118 nm and are composed of smaller Fe2O3@C secondary nanoparticles of 13.7 nm. Such a hierarchical nanostructure can increase the accessible surface area of the Fe2O3@C/CC electrode, leading to enhanced electrochemical efficiency for the Li+ insertion/deinsertion reaction. Furthermore, by carefully controlling dip-coating time, the Fe2O3@C nanoparticles are individually and uniformly distributed on the CC surface, which supplies expansion space for Li+ insertion and protects the electrode from structural cracks. Owing to these structural characteristics, the Fe2O3@C/CC anode material shows superior electrochemical properties for lithium-ion batteries. The first discharge capacity is as high as 1006 mAh g−1 at the current density of 0.2 A g−1, and it remains up to 1091 mAh g−1 after 100 charge/discharge cycles, implying a stable cycling ability.

Cross-Linking-Derived Synthesis of Porous CoxNiy/C Nanocomposites for Excellent Electromagnetic Behaviors

The magnet/dielectric composites with tunable structure and composition have drawn much attention because of their particular merits in magnetoelectric properties compared with the sole dielectric or magnetic composites. In addition, porous materials at the nanoscale can satisfy the growing requirements in many industries. Therefore, constructing porous metal alloy/carbon nanocomposites is to be an admirable option. Unfortunately, traditional synthesis methods involve multistep routes and complicated insert-and-remove templates approaches. Here we report a facile process to synthesize CoxNiy/C composites via a spontaneous cross-linking reaction and subsequent calcination process, during which multiple processes, including reducing polyvalent metal ions, forming alloy, and encapsulating alloy nanoparticles into porous carbon matrix, are achieved almost simultaneously. By adjusting the feed ratio of Co2+ to Ni2+ ions, controllable composition of CoxNiy/C composites can be gained. It should be noted that the CoxNiy/C composites are demonstrated to be excellent microwave absorbers from every aspect of assessment criteria including reflection loss, effective bandwidth, thickness, and weight of absorber. Our study opens up a promising technique for the synthesis of alloy/carbon composites with porous nanostructures with target functionalities.

PH-Responsive Tumor-Targetable Theranostic Nanovectors Based on Core Crosslinked (CCL) Micelles with Fluorescence and Magnetic Resonance (MR) Dual Imaging Modalities and Drug Delivery Performance.

The development of novel theranostic nanovectors is of particular interest in treating formidable diseases (e.g., cancers). Herein, we report a new tumor-targetable theranostic agent based on core crosslinked (CCL) micelles, possessing tumor targetable moieties and fluorescence and magnetic resonance (MR) dual imaging modalities. An azide-terminated diblock copolymer, N3-POEGMA-b-P(DPA-co-GMA), was synthesized via consecutive atom transfer radical polymerization (ATRP), where OEGMA, DPA, and GMA are oligo(ethylene glycol)methyl ether methacrylate, 2-(diisopropylamino)ethyl methacrylate, and glycidyl methacrylate, respectively. The resulting diblock copolymer was further functionalized with DOTA(Gd) (DOTA is 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrakisacetic acid) or benzaldehyde moieties via copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) chemistry, resulting in the formation of DOTA(Gd)-POEGMA-b-P(DPA-co-GMA) and benzaldehyde-POEGMA-b-P(DPA-co-GMA) copolymers. The resultant block copolymers co-assembled into mixed micelles at neutral pH in the presence of tetrakis[4-(2-mercaptoethoxy)phenyl]ethylene (TPE-4SH), which underwent spontaneous crosslinking reactions with GMA residues embedded within the micellar cores, simultaneously switching on TPE fluorescence due to the restriction of intramolecular rotation. Moreover, camptothecin (CPT) was encapsulated into the crosslinked cores at neutral pH, and tumor-targeting pH low insertion peptide (pHLIP, sequence: AEQNPIYWARYADWLFTTPLLLLDLALLVDADEGTCG) moieties were attached to the coronas through the Schiff base chemistry, yielding a theranostic nanovector with fluorescence and MR dual imaging modalities and tumor-targeting capability. The nanovectors can be efficiently taken up by A549 cells, as monitored by TPE fluorescence. After internalization, intracellular acidic pH triggered the release of loaded CPT, killing cancer cells in a selective manner. On the other hand, the nanovectors labeled with DOTA(Gd) contrast agents exhibited increased relaxivity (r1 = 16.97 mM−1·s−1) compared to alkynyl-DOTA(Gd) small molecule precursor (r1 = 3.16 mM−1·s−1). Moreover, in vivo MRI (magnetic resonance imaging) measurements revealed CCL micelles with pHLIP peptides exhibiting better tumor accumulation and MR imaging performance as well.

Thermogelling and chemoselectively cross-linked hydrogels for 3D bioprinting

Event Abstract Back to Event Thermogelling and chemoselectively cross-linked hydrogels for 3D bioprinting Tina Vermonden1, Kristel W. Boere1, Maarten M. Blokzijl1, 2, Jetze Visser2, J Elder A. Linssen2, Jos Malda2, 3 and Wim Hennink1 1 Utrecht Institute for Pharmaceutical Sciences (UIPS), Utrecht University, Department of Pharmaceutics, Netherlands 2 University Medical Center Utrecht, Department of Orthopedics, Netherlands 3 Utrecht University, Department of Equine Sciences, Netherlands Introduction: Chemoselectively cross-linked hydrogels have recently gained increasing attention for the development of novel, injectable biomaterials given their limited side reactions. Recently, oxo-ester mediated native chemical ligation (OMNCL) gained interest as polymer cross-linking mechanism for hydrogels in biomedical applications because of its chemoselective character and rapid reaction kinetics under physiological conditions without the need for catalysts[1]-[3]. The aim of this study was to investigate the properties of novel thermoresponsive, in situ forming hydrogels cross-linked by OMNCL regarding their gelation kinetics, cell viability and suitability as bioinks for 3D-printing. Methods: Polymers solutions were prepared from cysteine functionalized thermo-responsive polymers (PNC) mixed with poly(ethylene)glycol (PEG) or hyaluronic acid (HA), both carrying N-hydroxysuccinimide (NHS) functionalized carboxylic acid moieties with a total polymer concentration of 11.3 and 9.1 wt% respectively. To obtain hydrogels, the solutions were heated to 37 ºC followed by spontaneous crosslinking via the OMNCL mechanism. To monitor gelation kinetics and mechanical properties, rheological experiments were performed using a cone and plate equipped rheometer. Cell viability of chondrocytes encapsulated within the hydrogels was evaluated using live/dead staining. The polymeric solutions were allowed to pre-crosslink for 30 minutes before starting filament deposition using a 3D Discovery bioprinter to obtain porous scaffolds. Results: The storage modulus of OMNCL cross-linked hydrogels reached a value of 26 kPa after 4 hours, which was over a 100 times higher than hydrogels formed by solely thermal physical interactions. The degradation rates of these hydrogels under physiological conditions could be tailored from 12 days up to 6 months by incorporation of hydrolysable dimethyl-γ-butyrolactone acrylate (DBA) monomers in the thermosensitive triblock copolymer. Precisely designed printed 3D constructs were obtained by deposition of partially cross-linked gels on a heated plate of 37°C resulting in stabilization of the construct due to the thermosensitive nature of the hydrogel. Subsequently, further chemical cross-linking of the polymers proceeded after extrusion to form mechanically stable hydrogels that exhibited a storage modulus of 9 kPa after 3 hours with a porosity of 47.9 ± 2.3%. Figure 1: Printed hollow cone shape by thermogelling OMNCL hydrogel Additionally, the hydrogels were covalently grafted to NHS functionalized poly-e-caprolactone printed constructs, which resulted in enhanced mechanical resistance to external forces when compared to an absence of covalent linkages between the two types of materials. Printed thermoplastic constructs infused with hyaluronic acid containing gels showed high cell viability of chondrocytes, showing their potential use as bioink. Conclusions: The favorable and controllable properties of the studied OMNCL cross-linked hydrogels are attractive for further evaluation in biomedical applications. Moreover, 3D-printing of these pre-crosslinked two-component hydrogels allows for the creation of constructs with good shape fidelity. This work was supported by a grant from the Dutch government to the Netherlands Institute for Regenerative Medicine (NIRM, grant No. FES0908).; Part of the research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 309962 (HydroZones).

Spontaneous Cross-linking for Fabrication of Nanohybrids Embedded with Size-Controllable Particles.

This paper reports a versatile method to fabricate robust carbon/metal hybrids with ultrasmall particle and highly developed porous structure through a scalable and facile way. Alginate is used as the precursor for it could perform cross-linking reaction with different polyvalent metal ions to form gels. After simple freeze-drying and carbonization of the alginate-derived gels, we obtained the carbon/metal hybrids with fine nanostructure. Eleven kinds of metal ions were introduced to form gels and five kinds of the gels were carbonized to produce the carbon/metal hybrids. By adjusting the reaction condition, we could tune the size of the nanoparticles in the obtained hybrids. The obtained SnO2/C hybrid shows outstanding specific capacity, rate performance, and long cycle life when it is used as the anode materials of lithium ion batteries. The ultrasmall active nanoparticles were uniformly dispersed within an interconnected pore framework. It ensured a short diffusion and transportation distance of electrolyte ions to the surfaces of active nanoparticles. In addition, the robust carbon framework comprises of quasigraphitic carbon layers. It contributed to the high rate performance by providing excellent conductive pathways for electrons within the electrodes. This work provides a general method for fabrication of carbon/metal (oxide) hybrids with fine nanostructure for application in energy storage.

Fabrication of a live cell-containing multilayered polymer hydrogel membrane with micrometer-scale thickness to evaluate pharmaceutical activity

We propose a spinning-assisted layer-by-layer method for simple fabrication of a multilayered polymer hydrogel membrane that contains living cells. Hydrogel formation occurred based on the spontaneous cross-linking reaction between two polymers in aqueous solution. A water-soluble 2-methacryloyloxyethyl phosphorylcholine polymer bearing phenylboronic acid groups (PMBV) and poly(vinyl alcohol) (PVA) were used as polymers for hydrogel membrane formation. Changing the number of hydrogel membrane layers, polymer concentration, spinning rate, and processing time for diffusion-dependent gelation of PMBV and PVA facilitated the regulation of the multilayered polymer hydrogel membrane thickness and morphology. We concluded that a multilayered polymer hydrogel membrane prepared using 5.0 wt% PMBV and 5.0 wt% PVA at a spinning rate of 2000 rpm was suitable for precise spatial control of cells in single layers. This multilayered polymer hydrogel membrane was used to prepare a single cell-laden layer to minimize barriers to the diffusion of bioactive compounds while preserving the three-dimensional (3-D) context. The pharmaceutical effects of one of the anticancer agents, paclitaxel, on a human cervical cancer line, HeLa cells, were evaluated in vitro, and the usability of this culture model was demonstrated.

Combatting bacterial infections by killing persister cells with mitomycin C.

Persister cells are a multi-drug tolerant subpopulation of bacteria that contribute to chronic and recalcitrant clinical infections such as cystic fibrosis and tuberculosis. Persisters are metabolically dormant, so they are highly tolerant to all traditional antibiotics which are mainly effective against actively growing cells. Here, we show that the FDA-approved anti-cancer drug mitomycin C (MMC) eradicates persister cells through a growth-independent mechanism. MMC is passively transported and bioreductively activated, leading to spontaneous cross-linking of DNA, which we verify in both active and dormant cells. We find MMC effectively eradicates cells grown in numerous different growth states (e.g. planktonic cultures and highly robust biofilm cultures) in both rich and minimal media. Additionally, MMC is a potent bactericide for a broad range of bacterial persisters, including commensal Escherichia coli K-12 as well as pathogenic species of E. coli, Staphylococcus aureus and Pseudomonas aeruginosa. We also demonstrate the efficacy of MMC in an animal model and a wound model, substantiating the clinical applicability of MMC against bacterial infections. Therefore, MMC is the first broad-spectrum compound capable of eliminating persister cells, meriting investigation as a new approach for the treatment of recalcitrant infections.