Biocompatible Reaction Research Articles

Natural deep eutectic solvents as green and biocompatible reaction medium for carbonic anhydrase catalysis

Easy deactivation of free enzymes under non-native condition has become a stumbling block to the industrial application of biocatalysis. Natural deep eutectic solvent (NADES) has been exploited as a novel reaction medium for improving enzyme stability. The present work focused on preserving and enhancing the activity of carbonic anhydrase (CA) in a more economical and biocompatible NADES system. We synthesized six choline chloride/betaine-based NADES and analyzed the effects of compositions and concentrations of NADES on their physicochemical properties. The Bet-Gly (1: 2) NADES (55%) was proved to be more suitable as reaction medium for CA by analyzing enzyme activity in the presence of NADES. The enhancement in the stability of CA was found to be as a result of a three-dimensional hydrogen bonding network, rather than the individual or the synergistic effect of betaine and glyceride. The conformational change of CA to become more compact was confirmed both by fluorescence spectrum analysis and circular dichroism analysis. It is worth mentioning that a remarkable thermal stability was maintained when CA was incubated at temperature below 60 °C, and about 96% of activity was still restored in 55% NADES at 60 °C for 12 h.

Exporting Metal‐Carbene Chemistry to Live Mammalian Cells: Copper‐Catalyzed Intracellular Synthesis of Quinoxalines Enabled by N−H Carbene Insertions

AbstractImplementing catalytic organometallic transformations in living settings can offer unprecedented opportunities in chemical biology and medicine. Unfortunately, the number of biocompatible reactions so far discovered is very limited, and essentially restricted to uncaging processes. Here, we demonstrate the viability of performing metal carbene transfer reactions in live mammalian cells. In particular, we show that copper (II) catalysts can promote the intracellular annulation of alpha‐keto diazocarbenes with ortho‐amino arylamines, in a process that is initiated by an N‐H carbene insertion. The potential of this transformation is underscored by the in cellulo synthesis of a product that alters mitochondrial functions, and by demonstrating cell selective biological responses using targeted copper catalysts. Considering the wide reactivity spectrum of metal carbenes, this work opens the door to significantly expanding the repertoire of life‐compatible abiotic reactions.

Exporting Metal-Carbene Chemistry to Live Mammalian Cells: Copper-Catalyzed Intracellular Synthesis of Quinoxalines Enabled by N-H Carbene Insertions.

Implementing catalytic organometallic transformations in living settings can offer unprecedented opportunities in chemical biology and medicine. Unfortunately, the number of biocompatible reactions so far discovered is very limited, and essentially restricted to uncaging processes. Here, we demonstrate the viability of performing metal carbene transfer reactions in live mammalian cells. In particular, we show that copper (II) catalysts can promote the intracellular annulation of alpha‐keto diazocarbenes with ortho‐amino arylamines, in a process that is initiated by an N‐H carbene insertion. The potential of this transformation is underscored by the in cellulo synthesis of a product that alters mitochondrial functions, and by demonstrating cell selective biological responses using targeted copper catalysts. Considering the wide reactivity spectrum of metal carbenes, this work opens the door to significantly expanding the repertoire of life‐compatible abiotic reactions.

Selective Mitochondrial Protein Labeling Enabled by Biocompatible Photocatalytic Reactions inside Live Cells.

Biocompatible reactions are powerful tools to probe protein functions in their native environment. Due to the difficulty of penetrating the live-cell membrane and the complex intracellular environment, the biocompatible reactions inside live cells are challenging, especially at the subcellular level with spatial resolution. Here we report the first biocompatible photocatalytic azide conjugation reaction inside live cells to achieve the mitochondria-selective proteins labeling. The organic dyes acridine orange, fluorescein, and rhodamine 123 were developed as the biocompatible photocatalysts for the proteins labeling with aryl azides, which yielded benzazirines and ketenimines from triplet nitrenes for the protein nucleophilic residue trapping. The photocatalytic azide conjugation reaction with rhodamine 123 selectively labeled the mitochondrial proteins via the organic dye’s mitochondrial localization. In response to the mitochondrial stress induced by rotenone, this photocatalytic azide-promoted labeling method mapped the dynamic mitochondrial proteome changes with high temporal-spatial precision and identified several potential mitochondrial stress-response proteins for the first time. The high temporal-spatial precision of this photocatalytic azide-promoted labeling method holds excellent potential for intracellular protein network investigations.

Submerged culture of Penicillium sclerotiorum for production of rotiorin alkaloids by using biosynthetic and chemical catalytic cascade reactions

Red Monascus pigments, azaphilone alkaloids from Monascus sp., have been utilized as natural food colorant more than 1000 years in China. Other azaphilones are being developed as alternative sources of natural pigments. Rotiorin or rotiorin alkaloids are always only achieved by solid-state fermentation or liquid culture without stirring due to carbon/nitrogen metabolism affecting pH of the culture medium and the pH environment further affecting the rotiorin stability/reactivity. In the present work, based on the biocompatible reaction of rotiorin with primary amines using phosphate as catalyst, biosynthesis of rotiorin and chemical conversion of rotiorin into its alkaloids were designed as cascade reactions where rotiorin was prevented from degradation and rotiorin alkaloids were accumulated directly by submerged culture of P. sclerotiorum. This is a facile strategy for direct production of rotiorin alkaloids, which provides the precondition for exploiting rotiorin alkaloids as an alternative source of natural colorant.

Lipophilicity and Click Reactivity Determine the Performance of Bioorthogonal Tetrazine Tools in Pretargeted In Vivo Chemistry.

The development of highly selective and fast biocompatible reactions for ligation and cleavage has paved the way for new diagnostic and therapeutic applications of pretargeted in vivo chemistry. The concept of bioorthogonal pretargeting has attracted considerable interest, in particular for the targeted delivery of radionuclides and drugs. In nuclear medicine, pretargeting can provide increased target-to-background ratios at early time-points compared to traditional approaches. This reduces the radiation burden to healthy tissue and, depending on the selected radionuclide, enables better imaging contrast or higher therapeutic efficiency. Moreover, bioorthogonally triggered cleavage of pretargeted antibody–drug conjugates represents an emerging strategy to achieve controlled release and locally increased drug concentrations. The toolbox of bioorthogonal reactions has significantly expanded in the past decade, with the tetrazine ligation being the fastest and one of the most versatile in vivo chemistries. Progress in the field, however, relies heavily on the development and evaluation of (radio)labeled compounds, preventing the use of compound libraries for systematic studies. The rational design of tetrazine probes and triggers has thus been impeded by the limited understanding of the impact of structural parameters on the in vivo ligation performance. In this work, we describe the development of a pretargeted blocking assay that allows for the investigation of the in vivo fate of a structurally diverse library of 45 unlabeled tetrazines and their capability to reach and react with pretargeted trans-cyclooctene (TCO)-modified antibodies in tumor-bearing mice. This study enabled us to assess the correlation of click reactivity and lipophilicity of tetrazines with their in vivo performance. In particular, high rate constants (>50 000 M–1 s–1) for the reaction with TCO and low calculated logD7.4 values (below −3) of the tetrazine were identified as strong indicators for successful pretargeting. Radiolabeling gave access to a set of selected 18F-labeled tetrazines, including highly reactive scaffolds, which were used in pretargeted PET imaging studies to confirm the results from the blocking study. These insights thus enable the rational design of tetrazine probes for in vivo application and will thereby assist the clinical translation of bioorthogonal pretargeting.

Highly Efficient Production of Tailored Monascus Pigments by Using a Biocompatible Chemical Reaction Interfacing with Microbial Metabolism

A biocompatible reaction interfacing with microbial metabolism is an efficient approach for production of desired chemicals. Monascus pigments are a traditional natural food colorant from a microbial source. The major color components are red Monascus pigments (RMPs) with various primary amine resides as well as some minor components of yellow ones (YMPs) and orange ones (OMPs). Herein, we elucidate the pathway of OMP degradation involving nucleophilic attack of water on OMPs for the first time. On the basis of OMP degradation and the conversion of OMPs into RMPs sharing a similar reaction mechanism, i.e., nucleophilic attack of water or primary amine on the activated OMPs, we design cascade reactions including biosynthesis of OMPs and biocompatible chemical conversion of OMPs into the stable RMPs with a single glycine residue using a flexible combining chemocatalyst (phosphate ion) and micellar catalyst (Triton X-100). The cascade reactions ensure that OMPs maintain a very low concentration during microbial fermentation by rapid chemical conversion of OMPs into the stable RMPs. In this way, the metabolite profile of microbial fermentation is tailored to RMPs with a single glycine residue as the major color components while free of OMPs and YMPs. Meanwhile, the possible OMP degradation as well as feedback inhibition is eliminated, and a high concentration of RMPs 3.2 mM (1.4 g/L) is also achieved. Designing cascade reactions also has potential for the efficient microbial fermentation of other azaphilone alkaloids.

Biohybrid robotics: From the nanoscale to the macroscale.

Biohybrid robotics is a field in which biological entities are combined with artificial materials in order to obtain improved performance or features that are difficult to mimic with hand-made materials. Three main level of integration can be envisioned depending on the complexity of the biological entity, ranging from the nanoscale to the macroscale. At the nanoscale, enzymes that catalyze biocompatible reactions can be used as power sources for self-propelled nanoparticles of different geometries and compositions, obtaining rather interesting active matter systems that acquire importance in the biomedical field as drug delivery systems. At the microscale, single enzymes are substituted by complete cells, such as bacteria or spermatozoa, whose self-propelling capabilities can be used to transport cargo and can also be used as drug delivery systems, for in vitro fertilization practices or for biofilm removal. Finally, at the macroscale, the combinations of millions of cells forming tissues can be used to power biorobotic devices or bioactuators by using muscle cells. Both cardiac and skeletal muscle tissue have been part of remarkable examples of untethered biorobots that can crawl or swim due to the contractions of the tissue and current developments aim at the integration of several types of tissue to obtain more realistic biomimetic devices, which could lead to the next generation of hybrid robotics. Tethered bioactuators, however, result in excellent candidates for tissue models for drug screening purposes or the study of muscle myopathies due to their three-dimensional architecture. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Dichloroacetophenone Derivatives: A Class of Bioconjugation Reagents for Disulfide Bridging.

A mild and biocompatible method for the construction of disulfide bridging in peptides using dichloroacetophenone derivatives is developed. This method is highly selective (chemo, diastereo, regio, etc.) and atom economic and works under biocompatible reaction conditions (metal-free, water, pH 7, rt, etc.).

Polyethylene Glycol as a Green and Biocompatible Reaction Media for the Catalyst Free Synthesis of Organic Compounds

Replacing harmful organic solvents that caused environmental pollution with an alternative medium for the development of ideal synthetic strategies is one of the primary focal points of green chemistry. Utilizing polyethylene glycol (PEG) as a nonvolatile solvent and promotor for the evaluation of safe processes has made a considerable contribution to the reduction of pollution problems. The current review summarizes the recent well-known catalyst-free organic reaction performed in polyethylene glycol as a green and biocompatible reaction medium.

Single-Molecule Observation of Intermediates in Bioorthogonal 2-Cyanobenzothiazole Chemistry.

We report a single‐molecule mechanistic investigation into 2‐cyanobenzothiazole (CBT) chemistry within a protein nanoreactor. When simple thiols reacted reversibly with CBT, the thioimidate monoadduct was approximately 80‐fold longer‐lived than the tetrahedral bisadduct, with important implications for the design of molecular walkers. Irreversible condensation between CBT derivatives and N‐terminal cysteine residues has been established as a biocompatible reaction for site‐selective biomolecular labeling and imaging. During the reaction between CBT and aminothiols, we resolved two transient intermediates, the thioimidate and the cyclic precursor of the thiazoline product, and determined the rate constants associated with the stepwise condensation, thereby providing critical information for a variety of applications, including the covalent inhibition of protein targets and dynamic combinatorial chemistry.

Single‐Molecule Observation of Intermediates in Bioorthogonal 2‐Cyanobenzothiazole Chemistry

AbstractWe report a single‐molecule mechanistic investigation into 2‐cyanobenzothiazole (CBT) chemistry within a protein nanoreactor. When simple thiols reacted reversibly with CBT, the thioimidate monoadduct was approximately 80‐fold longer‐lived than the tetrahedral bisadduct, with important implications for the design of molecular walkers. Irreversible condensation between CBT derivatives and N‐terminal cysteine residues has been established as a biocompatible reaction for site‐selective biomolecular labeling and imaging. During the reaction between CBT and aminothiols, we resolved two transient intermediates, the thioimidate and the cyclic precursor of the thiazoline product, and determined the rate constants associated with the stepwise condensation, thereby providing critical information for a variety of applications, including the covalent inhibition of protein targets and dynamic combinatorial chemistry.

Choline chloride‐urea deep eutectic solvent as an efficient media for the synthesis of propargylamines via organocuprate intermediate

A facile method for the synthesis of various propargylamines derivatives with different structural parts has been reported. The reaction has consisted of one‐pot coupling between aldehydes, secondary amines and terminal alkynes using CuCl as a catalyst and choline chloride/urea DES as a cheap and biocompatible reaction media. The procedure is free of using toxic solvents and used CuCl as an available, inexpensive and non‐toxic catalyst. Using this methodology, 15 different propargylamine derivatives were successfully synthesized at 60 °C in 15 hr, mostly in good yields.

Oxidative Formation of Disulfide Bonds by a Chemiluminescent 1,2-Dioxetane under Mild Conditions.

The oxidation of alkyl thiols to disulfides has been achieved under mild conditions using a chemiluminescent 1,2-dioxetane as a stoichiometric oxidant. Besides the mild and biocompatible reaction conditions, this approach offers the possibility to monitor the presence of thiols through oxidation and chemiluminescence of the remaining dioxetane.

Illuminating Biology with Visible‐Light‐induced Biocompatible Reactions

AbstractYiyun Chen is a Professor at the Shanghai Institute of Organic Chemistry, Chinese Academy of Science, a member of the State Key Laboratory of Bioorganic and Natural Products Chemistry of China, and a joint Professor at ShanghaiTech University. He is a current member of the ChemPhotoChem Editorial Board.

Understanding gold nanoparticles interactions with chitosan: Crosslinking agents as novel strategy for direct covalent immobilization of biomolecules on metallic surfaces

The development of a new method for covalent immobilization of biomolecules on the surface of bare gold nanoparticles (AuNPs) by using crosslinking agents in one step is presented. A very compatible biopolymer such as chitosan has been used as a target molecule to probe the viability of the proposed methodology. Click chemistry, based on biocompatible reactions and coupling with 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide allow to analyze the covalent interactions between the metal nanoparticles and the biopolymer. Spectra deconvolution technique and Zeta potential measurements confirm the covalent interaction. The present study allows to quantify the proportion of AuNPs covalently adhered to the chitosan, which depends on the solution pH. The obtained results indicates that covalent interactions can be increased up to 25% in relation to total system interactions, which are mostly electrostatic. The proposed strategy opens up a new pathway for biomedical applications because the control of the chemical linkage can be directly performed on the nanoparticle surface without using any molecular intermediate, which may improve the encapsulation efficiency on drug delivery therapies.

Polythiophene-functionalized magnetic carbon nanotube-supported copper(I) complex: a novel and retrievable heterogeneous catalyst for the "Phosphine- and Palladium-Free" Suzuki-Miyaura cross-coupling reaction.

A simple preparation of catalysts with high catalytic activity and superior cycling stability is very desirable. In this contribution, magnetic carbon nanotube functionalized by polythiophene (CNT-Fe3O4-PTh) acts as an efficient and retrievable host for copper nanoparticles to prepare CNT-Fe3O4-PTh-Cu(I) as a nontoxic and inexpensive catalyst. FT-IR, TGA, EDX, VSM, XRD, FE-SEM, TEM, and AAS techniques were employed to characterize the structure of the synthesized magnetic heterogeneous nanocomposite. Thereafter, the catalytic application of the catalyst was evaluated for the phosphine- and palladium-free Suzuki-Miyaura cross-coupling reaction in water/ethanol as a green media in short reaction times with good to excellent yields. Various derivatives of biaryl compounds were synthesized by reaction of aryl halides and phenylboronic acid. Simple methodology and easy workup, short reaction times, elimination of volatile and toxic solvents, biocompatible reaction conditions, and high yields are some advantages of this protocol. Moreover, the catalyst showed a good reusability owing to its magnetic properties and was recycled several times without appreciable decrease in its catalytic efficiency. Copper(I) nanoparticles supported on magnetic carbon nanotube functionalized by polythiophene (CNT-Fe3O4-PTh-Cu(I)), was prepared and used for ligand- and palladiumfree Suzuki-Miyaura cross-coupling reaction in water/ethanol as a green media in short reaction times with good to excellent yields. Reusability and stability tests demonstrated that the as prepared catalyst can be recycled with a negligible loss of its activity.

In situ facile-forming chitosan hydrogels with tunable physicomechanical and tissue adhesive properties by polymer graft architecture

In situ forming hydrogels generated upon spontaneous and biocompatible reaction under physiological conditions are widely investigated as injectable and implantable biomaterials. However, it is still a significant challenge to control their mechanics while maintaining their gelation behavior, due to the interdependency between gelation kinetics and mechanics. Herein, physicomechanical properties of in situ forming chitosan hydrogels via Schiff base formation are tuned in a wide range, while maintaining gelation kinetics, via polymer graft architecture. By introducing poly(ethylene glycol) (PEG) grafts with varying lengths and densities, the resulting PEG-grafted chitosan (‘PEG-g-Cs’) not only dissolve readily in neutral aqueous media, but also effectively control the mechanical properties of hydrogels, while maintaining facile gelation kinetics. These properties are further controlled by the chain length of polymeric crosslinker, PEG-dialdehyde. In addition, tissue adhesive properties of the hydrogels are further examined using ex vivo and in vivo models for their potential applications as tissue sealants.

Tetrazine-Mediated Bioorthogonal System for Prodrug Activation, Photothermal Therapy, and Optoacoustic Imaging.

Bioorthogonal "bond cleavage" reactions hold great promise in a variety of biological applications such as controlled activation of the drug and probe, while the application of these biocompatible reactions in living animals is still in its infancy and has yet to be further explored. Herein we demonstrate a nanosized and two-component bioorthogonal system for tumor inhibition through the combined action of chemo- and photothermal therapy. The trigger of the system was fabricated by immobilizing PEGylated tetrazine on the gold nanorods, and the bioorthogonal prodrug was synthesized by caging the drug camptothecin with vinyl ether, followed by encapsulating it with phospholipid liposomes. The tetrazine-based trigger effectively mediates the bioorthogonal reaction and triggers the release of camptothecin for chemotherapy, and the gold nanorods exhibit high photothermal capability for photothermal therapy and for three-dimensional optoacoustic imaging. Upon injection into tumor-bearing mice, the two components accumulate in the tumor region and carry out a bioorthogonal reaction therein, hence releasing the parent drug. The combined actions of chemo- and photothermal therapy greatly inhibited tumor growth in mice. This strategy may afford a promising approach for achieving controlled release of an active drug in vivo through an alternative external stimulus-a bioorthogonal reaction.

Recent Developments in Metal-Catalyzed Bio-orthogonal Reactions for Biomolecule Tagging.

With the rapid advances in single-molecule and live-cell imaging studies to investigate biological problems, the role of chemical probes to monitor reactions in a live cell has considerably increased. However, selective labeling of a target protein or a specific residue is highly challenging due to the high complexity of the biological system. In particular, biological macromolecules (such as proteins, DNA, or RNA) share many functional groups that potentially cross-react with exogenous chemical probes. Thus, there are high demands for perfect biocompatible reactions utilizing biologically unavailable chemistry. Metal-catalyzed reactions have been extensively investigated as synthetic methodology studies, including initial attempts in applying the chemistry in aqueous solutions in vitro or even in biological conditions. Herein, the latest developments and progress in metal-catalyzed bio-orthogonal reactions for biomolecule labeling are summarized.