Biocompatible Conditions Research Articles

Aqueous olefin metathesis: recent developments and applications.

Olefin metathesis is one of the most powerful C–C double-bond-forming reactions. Metathesis reactions have had a tremendous impact in organic synthesis, enabling a variety of applications in polymer chemistry, drug discovery and chemical biology. Although challenging, the possibility to perform aqueous metatheses has become an attractive alternative, not only because water is a more sustainable medium, but also to exploit biocompatible conditions. This review focuses on the progress made in aqueous olefin metatheses and their applications in chemical biology.

Iridium‐Catalyzed Hydroxyl‐Enabled Cycloaddition of Azides and Alkynes

AbstractA novel iridium‐catalyzed hydroxyl‐enabled cycloaddition of azides and alkynes has been developed. In the presence of catalytic amount (2 mol%) of [Ir(cod)Cl]2, the 2‐alkynyl phenols would engage in a regioselective cycloaddition with various azides for rapid access to diverse triazoles, and the hydroxyl group acts as directing group to enable this reaction. The process is featured mild and biocompatible reaction condition with the achievement of brevity and diversity. Furthermore, the hydroxyl group offers ample opportunity for late‐stage divergent transformations of the products.magnified image

3D Droplet-Based Microfluidic Device Easily Assembled from Commercially Available Modules Online Coupled with ICPMS for Determination of Silver in Single Cell.

More recently, single-cell analysis based on ICPMS has made considerable headway while a challenge remains to differentiate single cell from doublets during the analysis. One burgeoning solution is to encapsulate single cell into droplets on the platform of the microfluidic chip. However, the manufacture of the droplet-based microfluidic chip requires sophisticated fabrication and limits its potential application. In this paper, we presented an off-the-shelf three-dimensional (3D) microfluidic device by assembling commercially available parts without any proficient manufacturing process. Uniform monodisperse microdroplet was generated from the 3D microfluidic device with a size variation of 1.5%, and the innner diameter of the 3D microfluidic device was the same as the nebulizer (150 μm). The proposed 3D microfluidic device-time-resolved ICPMS system was applied to detect silver in single AgNPs (51 nm), and the result is in good agreement with conventional acid digestion method, demonstrating the accuracy of the method. Silver uptake behaviors in HepG2 cells were then studied by incubating with Ag+ or AgNPs under biocompatible conditions. The results revealed that the cell-to-cell variability in terms of the diversity of cells incubated with AgNPs was wider than those cells incubated with Ag+ from the aspect of the content distribution of silver at the single-cell level.

Transition Metal‐Free Oxidative Coupling of Primary Amines in Polyethylene Glycol at Room Temperature: Synthesis of Imines, Azobenzenes, Benzothiazoles, and Disulfides

A transition metal‐free protocol has been developed for the oxidative coupling of primary amines to imines and azobenzenes, thiols to disulfides, and 2‐aminothiophenols to benzothiazoles, offering excellent yields. The advantageous features of the present environmentally benign methodology include the usage of biocompatible and green reaction conditions such as, solvent, room temperature reactions and transition metal‐free approach. Moreover, it offers a broader substrate scope.

Lysine Bioconjugation on Native Albumin with a Sulfonyl Acrylate Reagent.

This protocol details a novel bioconjugation strategy that uses a methanesulfonyl acrylate reagent that is directed to the most reactive lysine on human serum albumin, which enables the construction of chemically defined and stable bioconjugates. The reaction proceeds rapidly and a regioselective modification is achieved using a single molar equivalent of the reagent under biocompatible conditions (37°C, pH8.0). Importantly, the bioconjugate retains both the secondary structural content and function of the unmodified protein. During the reaction of the amino group of lysine and the sulfonyl acrylate reagent, methanesulfinic acid is released after the conjugate addition, which then generates an electrophilic acrylate moiety on the protein. This acrylate can be further used for site-specific protein labeling using a synthetic molecule bearing a reactive amine under biocompatible conditions (21°C, pH8.0).

"Off-on" switching of intracellular singlet oxygen release under biocompatible conditions.

Precise spatiotemporal control of singlet oxygen generation is of immense importance considering its involvement in photodynamic therapy. In this work, we present a rational design for an endoperoxide which is highly stable at ambient temperatures yet, can rapidly be converted into a highly labile endoperoxide, thus releasing the "stored" singlet oxygen on demand. The "off-on" chemical switching from the stable to the labile form is accomplished by the reaction with fluoride ions. The potential utility of controlled singlet oxygen release was demonstrated in cell cultures.

Combining sol-gel and microfluidics processes for the synthesis of protein-containing hybrid microgels.

Biocompatible chemical cross-linked hybrid polyethylene glycol-based hydrogels were obtained from a sol-gel process using bis-silylated molecular precursors in biocompatible conditions. This soft procedure (pH = 7.4, at 25 °C), allows the production of microgels by microfluidics and easy encapsulation of a model protein (Bovin Serum Albumine, BSA).

Biocompatibility conditions and biological activity of cobalt nanoparticles, depending on the size and concentration

Biological activity, the effect of 'small doses' and the biocompatibility of cobalt nanoparticles (NP) have been studied and proved, depending on the size and concentration of NP on white mustard. For nanoparticles with a particle size of 18-60 nm, the dependence of enzyme activity on concentration has general regularities and is consistent with the observed effect of 'small doses' in determining morpho-physiological parameters. Nanoparticles sized up to 20 nm show high activity at low concentrations up to the maximum concentration of 10 g/t. For nanoparticles with a size of 35-60 nm the concentration limit is much higher than 100 g/t. We assume that cobalt nanoparticles are a source of some additional amount of protons, which leads to a change in the hormonal status, stimulates or reduces the activity of certain endogenous phytohormones, depending on the size, physical and chemical characteristics of nanoparticles and concentration. Biologically active nanoparticles, acting on the level of phytohormones, indolylacetic acid (IAA) in particular, can influence the state of bio membranes and indirectly act as a regulator of protein-synthesising plant cells. This leads to the growth and development of living systems. The comprehensive study of the effect of different concentrations and sizes of nanoparticles on the activity of three antioxidant enzymes (SOD, catalase and peroxidase) has made it possible to establish that the peroxidase activity at maximum morpho-physiological parameters is high and decreases in 'dead zones' at both low and high concentrations of metal nanoparticles. The activity of SOD and catalase in the studied cultures decreased significantly under the conditions of maximum morpho-physiological parameters and sharply increased at concentrations greater than 100 g/t for nanoparticles 35-60 nm in size and above 10 g/t with a size of up to 20 nm. The conditions of biocompatibility of cobalt nanoparticles are shown.

Interfacial electron transfer between Geobacter sulfurreducens and gold electrodes via carboxylate-alkanethiol linkers: Effects of the linker length

Geobacter sulfurreducens (Gs) attachment and biofilm formation on self-assembled monolayers (SAMs) of carboxyl-terminated alkanethiol linkers with varied chain length on gold (Au) was investigated by electrochemical and microscopic methods to elucidate the effect of the surface modification on the current production efficiency of Gs cells and biofilms. At the initial stage of the cell attachment, the electrochemical activity of Gs cells at a submonolayer coverage on the SAM-Au surface was independent of the linker length. Subsequently, multiple potential cyclings indicated that longer linkers provided more biocompatible conditions for Gs cells than shorter ones. For Gs biofilms, on the other hand, the turnover current decreased exponentially with the linker length. During the biofilm formation, bacteria need to adjust from the initial planktonic state to an electrode-respiring state, which was triggered by a strong electrochemical stress found for shorter linkers, resulting in the formation of mature biofilms. Our results suggest that the initial cell attachment and the biofilm formation are two inherently different processes. Therefore, the effects of linker molecules, electron transfer efficiency and biocompatibility, must be explored simultaneously to understand both processes to increase the current production of electrogenic microorganisms in microbial fuel cells.

Evaluation of a Porous Bioabsorbable Interbody Mg-Zn Alloy Cage in a Goat Cervical Spine Model.

Purpose Bioabsorbable Mg-based implants were previously assessed due to their intrinsic advantages, but Mg-based cage related research is limited. The specific blood supply and stress of the intervertebral environment can affect the function of Mg-based implants. The objective of this study was to investigate the performance of a bioabsorbable Mg-Zn alloy cage in anterior cervical discectomy and fusion (ACDF) and evaluate the control of degradation of the Mg-Zn cage surface modified by microarc oxidation (MAO) technology containing Si under an intervertebral microenvironment. Methods Twenty-four goats were divided into four groups according to the experimental period and all underwent ACDF at C2-3 and C4-5 with porous Mg-Zn cage covered with a MAO/Si-containing coating in one intervertebral space and with autologous iliac bone in another space. After 3, 6, 12, or 24 weeks after operation, the cervical spine specimens were harvested to evaluate the biocompatibility, fusion status, and degradation conditions using blood analysis, radiology, biomechanical testing, histology, and micro-CT. Results The Mg-Zn cages showed ideal biocompatibility and biomechanical characterization; however, the fusion state, as evaluated with radiology and histology, was not acceptable. Modified by the MAO/Si-containing coating, the degradation rate of the Mg-Zn cages was controllable but slower than expected. Conclusion MAO/Si-containing coating Mg-Zn alloy cages demonstrated excessive control of degradation and fusion failure after 24 weeks postoperatively. We conclude that further studies should be designed to improve the using of Mg-based materials at the intervertebral space.

Visible Light-Initiated Bioorthogonal Photoclick Cycloaddition.

Here we report a visible light-triggered, catalyst free bioorthogonal reaction that proceeds via a distinct pathway from reported bioorthogonal reactions. The prototype of this bioorthogonal reaction was the photocycloaddition of 9,10-phenanthrenequinone with electron-rich alkenes to form fluorogenic [4+2] cycloadducts. The bioorthogonal photoclick cycloaddition was readily initiated using a conventional visible light source such as a hand-held LED lamp. The reaction proceeded rapidly under biocompatible conditions, without observable competition from side reactions such as nucleophilic additions by water or common nucleophilic species. The bioorthogonal functionality in this reaction did not cross react with various alkynes and electron-deficient alkenes such as monomethyl fumarate. We demonstrated orthogonal labeling of two proteins using this reaction together with a strain promoting azide-alkyne click reaction or the UV-triggered reaction of tetrazole with monomethyl fumarate. The application of this reaction in the temporal and spatial labeling of live cells was also demonstrated.

Electrically Switchable Monostable Actuatoric Polymer-Based Nanovalve Arrays with a Long-Term Stability.

Here we present a novel electrically switchable nanovalve array based on an intrinsic conductive polymer that has the capabilities to change its volume depending on its redox state. The polymer is created by anodic deposition of a sodium dodecylbenzenesulfonate (DBS)-doped polypyrrole (PPy). Optimization of the DBS-doped PPy layers revealed an actuatoric performance of up to 10% out of plane volume change. More interestingly, the electrochemical characterization revealed an actuatoric monostable polymer that could be used to fabricate nanovalve arrays that have a native opened state when no potential is applied and that can be closed when a reductive potential is applied. As a proof of concept, Atto488-labeled biotin (Biotin-Atto488) was used as a model compound and defined nanovalve arrays with nanopores in the range of 10 nm in diameter (opened state) were fabricated. Afterward, we were able to successfully prove the functionality of our nanovalve array by monitoring the flow-through rates of the Biotin-Atto488. More strikingly, we could demonstrate for the first time the robust and long-term stability of our nanovalve array without any performance loss for at least 72 h and retention capabilities of up to 90%. Furthermore, the demonstrated long-term stability was achieved under biocompatible conditions without the need of toxic dopant supplementation of the flow-through solution. Thus, our novel functional long-term stable nanovalve array offers the capabilities for practical applications.

Amino-Acid-Catalyzed Direct Aldol Bioconjugation.

A site-specific bioconjugation was developed based on direct aldol coupling using amino-acid-derived organocatalysts. The functionalization exhibits fast kinetics and occurs under mild, biocompatible conditions (viz., aqueous media, moderate temperature, and neutral pH). The resulting bioconjugates were found to be stable toward abundant aldolase enzymes, as well as acidic and basic pH. The methodology was demonstrated through conjugation of a variety of small molecules, dyes, and peptides to proteins, including a single-domain antibody, which was then used for cellular imaging.

Catalytic N-modification of \u03b1-amino acids and small peptides with phenol under bio-compatible conditions

The functionalization of α-amino acids and peptides provides the opportunity to tailor the properties of these biomolecules for diverse applications in chemistry and biology. Previous methods for N-modification involve the use of aliphatic alcohols, aldehydes, or halides. Alternatively, phenolic compounds are more desirable alkylating reagents as they constitute the backbone of lignin, making them an attractive bio-renewable resource. Here we report a method to N-modify 17 out of the 20 amino acids with phenol or derivatives, with water as the sole by-product. N-arylation is achieved using 2-cyclohexen-1-one and cyclohexanone as the coupling partners. Notably, phenol is successfully used to N-cyclohexylate α-amino acids and small peptides in excellent yields under bio-compatible conditions without racemization.

One-Step Assembly of a Biomimetic Biopolymer Coating for Particle Surface Engineering.

Advances in material design and applications are highly dependent on the development of particle surface engineering strategies. However, few universal methods can functionalize particles of different compositions, sizes, shapes, and structures. The amyloid-like lysozyme assembly-mediated surface functionalization of inorganic, polymeric or metal micro/nanoparticles in a unique amyloid-like phase-transition buffer containing lysozyme are described. The rapid formation of a robust nanoscale phase-transitioned lysozyme (PTL) coating on the particle surfaces presents strong interfacial binding to resist mechanical and chemical peeling under harsh conditions and versatile surface functional groups to support various sequential surface chemical derivatizations, such as radical living graft polymerization, the electroless deposition of metals, biomineralization, and the facile synthesis of Janus particles and metal/protein capsules. Being distinct from other methods, the preparation of this pure protein coating under biocompatible conditions (e.g., neutral pH and nontoxic reagents) provides a reliable opportunity to directly modify living cell surfaces without affecting their biological activity. The PTL coating arms yeasts with a functional shell to protect their adhered body against foreign enzymatic digestion. The PTL coating further supports the surface immobilization of living yeasts for heterogeneous microbial reactions and the sequential surface chemical derivatization of the cell surfaces, e.g., radical living graft polymerization.

Simultaneous production of antioxidants and starch from the microalga Chlorella sorokiniana

In recent years, microalgae have gained considerable importance as potential source of biofuels and bioplastics. However, these markets are still developing, as the high costs of cultivation ask for exploiting microalgae into new areas and with a biorefinery approach towards a multicomponent cascade extraction process. Here, a sequential processing strategy was used to extract starch with high yield from Chlorella sorokiniana under biocompatible conditions. The extract residue was then tested as a potential source of antioxidants. We found a strong protective activity of the extract residue towards oxidative stress in vitro on human colon cancer cells and in vivo on Caenorhabditis elegans nematodes, by inhibiting ROS production and activating DAF-16/FOXO transcription factor pathway. A pool of molecules from three different classes (fatty acids, photosynthetic pigments and carotenoids) was identified as responsible for the antioxidant activity. To our knowledge, this is the first report on the obtainment, from a “waste” fraction, of high value products endowed with antioxidant activity tested in cell-based models and in vivo.

N,O-Iminoboronates: Reversible Iminoboronates with Improved Stability for Cancer Cells Targeted Delivery.

Herein a new class of iminoboronates obtained from 2-acetylbenzene boronic acids and aminophenols is presented. The N,O-ligand topology enabled the formation of an additional B-O bond that locks the boron center in a tetrahedral geometry. This molecular arrangement decisively contributes to improve the construct's stability in biocompatible conditions and retaining the iminoboronate reversibility in more acidic environments. 2-Acetylbenzene boronic acid was reacted with a fluorescent amino-coumarin to yield a stable and non-fluorescent N,O-iminoboronate. This mechanism was further used to assemble a folate receptor targeting conjugate that selectively delivered the fluorescent amino-coumarin to MDA-MB-231 human breast cancer cells.

Electrochemical CO2 reduction to formate at indium electrodes with high efficiency and selectivity in pH neutral electrolytes

Electrochemical reduction of CO2 is promising for a bio-based economy as it combines utilization of CO2 as feedstock and provides a pathway for the utilization and (temporary) storage of electric energy. Among different products formate (HCOO-) can be produced with high rates and selectivity using indium as electrocatalyst. This can be achieved at mild biocompatible reaction conditions, e.g. ambient temperature, ambient pressure and neutral pH. Formate can serve as a source of carbon and energy for the biosynthesis of energy carriers or chemicals. However, the in situ interfacing of electrochemical CO2 reduction and biosynthesis creates challenges for electrochemical engineering. It is demonstrated that the electrode potential is the main steering parameter affecting the columbic efficiency, selectivity and rate of formate production in NaHCO3 electrolyte solution at biocompatible conditions. Coulombic efficiencies and formate production rates of 94.5 ± 2% and 0.136 ± 0.016 mmol h-1 cm-2 (at -2.2 vs. Ag/AgCl and ĸ = 10 mS cm-1), respectively, were achieved. Further, increasing the conductivity using inert electrolytes can enhance formate space-time yields up to 0.254 ± 0.031 mmol h-1 cm-2. Surprisingly, high NaHCO3 concentrations do not further increase formate production which supports that HCO3- is not electrochemically converted but only acting as CO2/H+ reservoir. Based on kinetic modeling insight on the inter-conversion of the carbonaceous species by CO2 sparging of the electrolyte solution is provided. Importantly, the influence of O2 on the electrochemical CO2 reduction was revealed to be marginal. This study, providing principles on the engineering of electrochemical CO2 reduction to formate for future interfacing to biosynthesis, demonstrates its feasibility to become technologically relevant.

Lipase@ZIF-8 nanoparticles-based biosensor for direct and sensitive detection of methyl parathion

Organophosphorus pesticides especially p-nitrophenyl pesticides (methyl parathion) have neurotoxic effects and it is a difficult to remove organophosphorus pesticides residues from contaminated water. Present work has developed a sensitive, direct and rapid lipase@ZIF-8/chitosan/glassy carbon electrode (GCE) and lipase@amine-modified ZIF-8(An-ZIF-8)/chitosan/GCE biosensors for detection of methyl parathion. ZIF-8 and An-ZIF-8 nanoparticles which are a type of metal-organic frameworks with large surface area and high porosity have been facilely prepared under mild biocompatible conditions and used as lipase immobilization matrixes in the biosensors. The optimized lipase@ZIF-8/chitosan/GCE and lipase@An-ZIF-8/chitosan/GCE biosensors can detect methyl parathion with a wide linear range, good repeatability, recovery and limit of detection as low as 0.28 μM. The as-prepared biosensors can be stored in 0.05 M PBS (pH 7) at 4 °C and reused for at least 20 days with a retainment of at least 80% of its initial response to methyl parathion. This indicated that both ZIF-8/chitosan and An-ZIF-8/chitosan are suitable for immobilization of lipase that favors generation of p-nitrophenol from methyl parathion; and subsequent electrochemical oxidation and electron transfer of the p-nitrophenol.

Reversible Social Self-Sorting of Colloidal Cell-Mimics with Blue Light Switchable Proteins.

Toward the bottom-up assembly of synthetic cells from molecular building blocks, it is an ongoing challenge to assemble micrometer sized compartments that host different processes into precise multicompartmental assemblies, also called prototissues. The difficulty lies in controlling interactions between different compartments dynamically both in space and time, as these interactions determine how they organize with respect to each other and how they work together. In this study, we have been able to control the self-assembly and social self-sorting of four different types of colloids, which we use as a model for synthetic cells, into two separate families with visible light. For this purpose we used two photoswitchable protein pairs (iLID/Nano and nHagHigh/pMagHigh) that both reversibly heterodimerize upon blue light exposure and dissociate from each other in the dark. These photoswitchable proteins provide noninvasive, dynamic, and reversible remote control under biocompatible conditions over the self-assembly process with unprecedented spatial and temporal precision. In addition, each protein pair brings together specifically two different types of colloids. The orthogonality of the two protein pairs enables social self-sorting of a four component mixture into two distinct families of colloidal aggregates with controlled arrangements. These results will ultimately pave the way for the bottom-up assembly of multicompartment synthetic prototissues of a higher complexity, enabling us to control precisely and dynamically the organization of different compartments in space and time.