Molecular engineering and live-cell imaging in mechanobiology

Cells in the body are exposed to physiological and pathophysiological stimuli that encompass both chemical and mechanical factors,which coordinately modulate cellular functions. Compared to the large amount of information on cellular re-

Molecular engineering of antibodies for site-specific conjugation to lipid polydopamine hybrid nanoparticles

Conjugation of antibodies to nanoparticles allows specific cancer targeting,but conventional conjugation methods generate heterogeneous conjugations that cannot guarantee the optimal orientation and functionality of the conjugated antibody.Here,a molecular engineering technique was used for sitespecific conjugation of antibodies to nanoparticles.We designed an anti-claudin 3(CLDN3)antibody containing a single cysteine residue,h4 G3 cys,then linked it to the maleimide group of lipid polydopamine hybrid nanoparticles(LPNs).Because of their negatively charged lipid coating,LPNs showed high colloidal stability and provided a functional surface for site-specific conjugation of h4 G3 cys.The activity of h4 G3 cys was tested by measuring the binding of h4 G3 cys-conjugated LPNs(C-LPNs)to CLDN3-positive tumor cells and assessing its subsequent photothermal effects.C-LPNsspecifically recognized CLDN3-overexpressing T47 D breast cancer cells but not CLDN3-negative Hs578 T breast cancer cells.High binding of C-LPNs to CLDN3-overexpressing T47 D cells resulted in significantly higher temperature generation upon NIR irradiation and potent anticancer photothermal efficacy.Consistent with this,intravenous injection of C-LPNsin a T47 D xenograft mouse model followed by NIR irradiation caused remarkable tumor ablation compared with other treatments through high temperature increases.Our results establish an accurate antibody-linking method and demonstrate the possibility of developing therapeutics using antibody-guided nanoparticles.

CsPbBr_(3) quantum dots photodetectors boosting carrier transport via molecular engineering strategy

Perovskite quantum dots (PQDs) require ligands on their surfaces to passivate defects and prevent aggregation. However, the ligands construct the interface relationship between the PQDs, which may seriously hinder the carrier transport. Hence, we propose a molecular engineering strategy of using 3,4-ethylenedioxythiophene (EDOT) to perfectly solve this problem, benefiting from its high conjugation and passivation ability to CsPbBr_(3) PQDs. Furthermore, EDOT on the surface of PQDs can be in-situ polymerized under the photocurrent of the photodetector, thus interconnecting the PQDs which enhanced the performance of the photodetectors up to 178% of its initial performance. We have thoroughly investigated the electropolymerization process of EDOT and its passivation effect on PQDs. The simple lateral photodetector based on EDOT PQDs exhibits a high responsivity of 11.96 A/W, which is 104 times higher than that of oleic acid caped PQDs. Due to the protection of poly(3,4-ethylenedioxythiophene) (PEDOT), the photodetector prepared from EDOT PQDs exhibited very high stability, retaining 94% of its performance after six months in air. This strategy provides a solution for the application of PQDs in high performances and stable optoelectronic devices.

Molecular Engineering of Novel Fluorophores for High-Contrast Bioimaging

Fluorophores play a significant role in achieving high-contrast imaging in complex physiological environment.Herein,we present the results of our studies on the development of various fluorophores,such as anti-solvatochromic fluorophores,long wavelength emission two-photon fluorophores,large Stokes shift fluorophores and solid-state fluorophores,to achieve high-contrast bioimaging in physiological environments.in this study,we have primarily focused on the design,optical performance,imaging mechanisms,and the applications of these fluorophores with respect to complex physiological conditions.

Molecular engineering of Y-series acceptors for nonfullerene organic solar cells

The power conversion efficiencies(PCEs)of single-junction organic solar cells(OSCs)have surpassed 19%,owing to the emerging Y-series nonfullerene acceptors(NFAs).Undoubtedly,the power and flexibility of chemical design has been a strong driver for this rapid efficiency improvement in the OSC field.Over the course of the past 3 years,a variety of modifications have been made to the structure of the Y6 acceptor,and a large number of Y-series NFAs have been reported to further improve performance.Herein,we present our insights into the rationale behind the Y6 acceptor and discuss the design principles toward high-performance Y-series NFAs.It is clear that structural modifications through choice of heteroatom,soluble chains,πspacers,central cores,and end groups alter the material characteristics and properties,contributing to distinctive photovoltaic performance.Subsequently,we analyze various design strategies of Y-series-containing materials,including polymerized small-molecule acceptors(PSMA),non-fused-ring acceptors(NFRA),and all-fused-ring acceptors(AFRA).This review is expected to be of value in providing effective molecular design strategies for high-performance NFAs in future innovations.

Surface Molecular Encapsulation with Cyclodextrin in Promoting the Activity and Stability of Fe Single-Atom Catalyst for Oxygen Reduction Reaction

Fe single-atom catalysts(Fe-SACs)have been extensively studied as a highly efficient electrocatalyst toward the oxygen reduction reaction(ORR).Nonetheless,they suffer from stability issue induced by dissolution of Fe metal center and the OH^(−)blocking.Herein,a surface molecular engineering strategy is developed by usingβ-cyclodextrins(CDs)as a localized molecular encapsulation.The CD-modified Fe-SAC(Fe-SNC-β-CD)shows obviously improved activity toward the ORR with 0.90 V,4.10 and 4.09 mA cm^(-2)for E_(1/2),J_(0)and Jk0.9,respectively.Meanwhile,the Fe-SNC-β-CD shows the excellent long-term stability against aggressive stress and the poisoning.It is confirmed through electrochemical investigation that modification ofβ-CD can,on one hand,regulate the atomic Fe coordination chemistry through the interaction between the CD and FeN_(x) moiety,while on the other mitigate the strong adsorption of OH^(−)and function as protective barrier against the poisoning molecules leading to enhanced ORR activity and stability for the Fe-SACs.The molecular encapsulation strategy demonstrates the uniqueness of post-pyrolysis surface molecular engineering for the design of single-atom catalyst.

Expression of Transforming Growth Factor β_(1) in Mesenchymal Stem Cells: Potential Utility in Molecular Tissue Engineering for Osteochondral Repair

The feasibility of using gene therapy to treat full-thickness articular cartilage defects was investigated with respect to the transfection and expression of exogenous transforming growth factor(TGF)-β_(1)genes in bone marrow-derived mesenchymal stem cells(MSCs)in vitro.The full-length rat TGF-β_(1)cDNA was transfected to MSCs mediated by lipofectamine and then selected with G418,a synthetic neomycin analog.The transient and stable expression of TGF-β_(1)by MSCs was detected by using immunohistochemical staining.The lipofectamine-mediated gene therapy efficiently transfected MSCs in vitro with the TGF-β_(1)gene causing a marked up-regulation in TGF-β_(1)expression as compared with the vector-transfected control groups,and the increased expression persisted for at least 4 weeks after selected with G418.It was suggested that bone marrow-derived MSCs were susceptible to in vitro lipofectamine mediated TGF-β_(1)gene transfer and that transgene expression persisted for at least 4 weeks.Having successfully combined the existing techniques of tissue engineering with the novel possibilities offered by modern gene transfer technology,an innovative concept,i.e.molecular tissue engineering,are put forward for the first time.As a new branch of tissue engineering,it represents both a new area and an important trend in research.Using this technique,we have a new powerful tool with which:(1)to modify the functional biology of articular tissue repair along defined pathways of growth and differentiation and(2)to affect a better repair of full-thickness articular cartilage defects that occur as a result of injury and osteoarthritis.

Molecular Tissue Engineering: Applications for Modulation of Mesenchymal Stem Cells Proliferation by Transforming Growth Factor β_1 Gene Transfer

The effect of transforming growth factor β 1 (TGF β 1 ) gene transfection on the proliferation of bone marrow derived mesenchymal stem cells (MSC S ) and the mechanism was investigated to provide basis for accelerating articular cartilage repairing using molecular tissue engineering technology. TGF β 1 gene at different doses was transduced into the rat bone marrow derived MSCs to examine the effects of TGF β 1 gene transfection on MSCs DNA synthesis, cell cycle kinetics and the expression of proliferating cell nuclear antigen (PCNA). The results showed that 3 μl lipofectamine mediated 1 μg TGF β 1 gene transfection could effectively promote the proliferation of MSCs best; Under this condition (DNA/Lipofectamine=1μg/3μl), flow cytometry and immunohistochemical analyses revealed a significant increase in the 3 H incorporation, DNA content in S phase and the expression of PCNA. Transfection of gene encoding TGF β 1 could induce the cells at G0/G1 phase to S1 phase, modulate the replication of DNA through the enhancement of the PCNA expression, increase the content of DNA at S1 phase and promote the proliferation of MSCs. This new molecular tissue engineering approach could be of potential benefit to enhance the repair of damaged articular cartilage, especially those caused by degenerative joint diseases.

Molecular Tissue Engineering:Concepts,Status and Challenge

Tissue engineering has confronted many difficulties mainly as follows:1)How to modulate the adherence,proliferation,and oriented differentiation of seed cells, especially that of stemcells. 2) Massive preparation and sustained controllable delivery of tissue inducing factors or plasmid DNA, such as growth factors, angiogenesis stimulators,and so on. 3) Development of 'intelligent biomimetic materials' as extracellular matrix with a good superficial and structural compatibility as well as biological activity to stimulate predictable, controllable and desirable responses under defined conditions.Molecular biology is currently one of the most exciting fields of research across life sciences,and the advances in it also bring a bright future for tissue engineering to overcome these difficulties.In recent years,tissue engineering benefits a lot from molecular biology.Only a comprehensive understanding of the involved ingredients of tissue engineering (cells,tissue inducing factors,genes,biomaterials) and the subtle relationships between them at molecular level can lead to a successful manipulation of reparative processes and a better biological substitute.Molecular tissue engineering,the offspring of the tissue engineering and molecular biology,has gained an increasing importance in recent years.It offers the promise of not simply replacing tissue,but improving the restoration.The studies presented in this article put forward this new concept for the first time and provide an insight into the basic principles,status and challenges of this emerging technology.

Photophysical Properties and Photovoltaic Performance of Sensitizers with a Bipyrimidine Acceptor

Molecular engineering is a crucial strategy for improving the photovoltaic performance of dye-sensitized solar cells(DSSCs). Despite the common use of the donor-π bridge-acceptor architecture in designing sensitizers, the underlying structure-performance relationship remains not fully understood. In this study, we synthesized and characterized three sensitizers: MOTP-Pyc, MOS_(2)P-Pyc, and MOTS_(2)P-Pyc, all featuring a bipyrimidine acceptor. Absorption spectra, cyclic voltammetry, and transient photoluminescence spectra reveal a photo-induced electron transfer(PET) process in the excited sensitizers. Electron spin resonance spectroscopy confirmed the presence of charge-separated states. The varying donor and π-bridge structures among the three sensitizers led to differences in their conjugation effect, influencing light absorption abilities and PET processes and ultimately impacting the photovoltaic performance. Among the synthesized sensitizers, MOTP-Pyc demonstrated a DSSC efficiency of 3.04%. Introducing an additional thienothiophene block into the π-bridge improved the DSSC efficiency to 4.47% for MOTS_(2)P-Pyc. Conversely, replacing the phenyl group with a thienothiophene block reduced DSSC efficiency to 2.14% for MOS_(2)P-Pyc. Given the proton-accepting ability of the bipyrimidine module, we treated the dye-sensitized TiO_(2) photoanodes with hydroiodic acid(HI), significantly broadening the light absorption range. This treatment greatly enhanced the short-circuit current density of DSSCs owing to the enhanced electron-withdrawing ability of the acceptor. Consequently, the HI-treated MOTS_(2)P-Pyc-based DSSCs achieved the highest power conversion efficiency of 7.12%, comparable to that of the N719 dye at 7.09%. This work reveals the positive role of bipyrimidine in the design of organic sensitizers for DSSC applications.

Machine learning for molecular thermodynamics

Thermodynamic properties of complex systems play an essential role in developing chemical engineering processes.It remains a challenge to predict the thermodynamic properties of complex systems in a wide range and describe the behavior of ions and molecules in complex systems.Machine learning emerges as a powerful tool to resolve this issue because it can describe complex relationships beyond the capacity of traditional mathematical functions.This minireview will summarize some fundamental concepts of machine learning methods and their applications in three aspects of the molecular thermodynamics using several examples.The first aspect is to apply machine learning methods to predict the thermodynamic properties of a broad spectrum of systems based on known data.The second aspect is to integer machine learning and molecular simulations to accelerate the discovery of materials.The third aspect is to develop machine learning force field that can eliminate the barrier between quantum mechanics and all-atom molecular dynamics simulations.The applications in these three aspects illustrate the potential of machine learning in molecular thermodynamics of chemical engineering.We will also discuss the perspective of the broad applications of machine learning in chemical engineering.

Vacuum residue coking process simulation using molecular-level kinetic model coupled with vapor-liquid phase separation

In this work,a molecular-level kinetic model was built to simulate the vacuum residue(VR)coking process in a semi-batch laboratory-scale reaction kettle.A series of reaction rules for heavy oil coking were summarized and formulated based on the free radical reaction mechanism.Then,a large-scale molecularlevel reaction network was automatically generated by applying the reaction rules on the vacuum residue molecules.In order to accurately describe the physical change of each molecule in the reactor,we coupled the molecular-level kinetic model with a vapor–liquid phase separation model.The vapor–liquid phase separation model adopted the Peng-Robinson equation of state to calculate vapor–liquid equilibrium.A separation efficiency coefficient was introduced to represent the mass transfer during the phase separation.We used six sets of experimental data under various reaction conditions to regress the model parameters.The tuned model showed that there was an excellent agreement between the calculated values and experimental data.Moreover,we investigated the effect of reaction temperature and reaction time on the product yields.After a comprehensive evaluation of the reaction temperature and reaction time,the optimal reaction condition for the vacuum residue coking was also obtained.

Control of surface wettability via strain engineering

Reversible control of surface wettability has wide applications in lab-on-chip systems, tunable optical lenses, and microfluidic tools. Using a graphene sheet as a sam- ple material and molecular dynamic simulations, we demon- strate that strain engineering can serve as an effective way to control the surface wettability. The contact angles 0 of water droplets on a graphene vary from 72.5° to 106° under biaxial strains ranging from -10% to 10% that are applied on the graphene layer. For an intrinsic hydrophilic surface （at zero strain）, the variation of 0 upon the applied strains is more sensitive, i.e., from 0° to 74.8°. Overall the cosines of the contact angles exhibit a linear relation with respect to the strains. In light of the inherent dependence of the contact an- gle on liquid-solid interfacial energy, we develop an analytic model to show the cos 0 as a linear function of the adsorption energy Eads of a single water molecule over the substrate sur- face. This model agrees with our molecular dynamic results very well. Together with the linear dependence of Eads on bi- axial strains, we can thus understand the effect of strains on the surface wettability. Thanks to the ease of reversibly ap- plying mechanical strains in micro/nano-electromechanical systems, we believe that strain engineering can be a promis- ing means to achieve the reversibly control of surface wetta- bility.

Engineering Mechanical Strong Biomaterials Inspired by Structural Building Blocks in Nature

The intricate multiscale architectures in natural structural building blocks provide many sources of inspiration for the designs of artificial biomaterials.In nature,the assembly of highly ordered molecular crystals and amorphous aggregates often derives from inter-and intra-molecular interactions of biomacromolecules,e.g.,proteinaceous materials.The structural biomaterials derived from the protein self-assembly behave with remarkable mechanical performance.However,there is still a grand challenge to mimic the mechanical properties of natural protein-based biomaterials in a rational design fashion to yield comparable man-made synthetic ensembles.In this review,a brief perspective on current challenges and advances in terms of bioinspired structural materials is presented.We outline a framework for mimicking protein self-assembly of natural building blocks across multiscale and highlight the critical role of synthetic biology and chemical modifications in material biosynthesis.Particularly,we focus on the design and promising applications of protein-based fibers,adhesives,dynamic hydrogels and engineered living materials,in which natural mechanical functions are effectively reproduced.

Spectral and biodistributional engineering of deep near-infrared chromophore

Fluorescence-guided surgery calls for development of near-infrared fluorophores.Despite the wide-spread application and a safe clinical record of Indocyanine Green(ICG),its maximal absorption wavelength at780 nm is rather short and longer-wavelength dyes are desired to exploit such benefits as low phototoxicity and deep penetration depth.Here,we report ECY,a stable deep near-infrared(NIR)fluorochromic scaffold absorbing/emitting at 836/871 nm with a fluorescence quantum yield of 16%in CH_(2)Cl_(2).ECY was further rationally engineered for biological distribution specificity.Analogous bearing different numbers of sulfonate group or a polyethylene glycol chain were synthesized.By screening this focused library upon intravenous injection to BALB/c mice,ECYS2 was identified to be a suitable candidate for bioimaging of organs involved in hepatobiliary excretion,and ECYPEG was found to be a superior candidate for vasculature imaging.They have potentials in intraoperative imaging.

Gene Cloning,Expression and Immunoreactivity of a Single Chain-Fv-Fragment Antibody PS-9

The gene encoding the heavy- and light-chain Fv regions of monoclonal antibody PS-9, which recognizes a cancer-associated antigen S-Tn on the most adenocarcinoma, was cloned by PCR techniques. The light and heavy chains were connected by a flexible linker to form a single chain variable fragment (ScFv) gene with 720 bp, which was in turn fused to pCANTAB 5 phage. The single chain Fv was expressed as fusion protein displayed on the phage surface. The phagemid is used to transform competent E. Coli TG1 cells, then infected with M13K07 helper phage to rescue the phagemid and antibody ScFv gene. All randomized 12 clones were shown reacting with colon cancer cell line Ls174t, which expresses S-Tn antigen. The recombinant phage has been infected E. Coli HB2151 cells to produce soluble antibody, which can be used for immunodetection and immunotherapy for cancer.

Molecular design of an ultra-strong tissue adhesive hydrogel with tunable multifunctionality

Designing adhesive hydrogels with optimal properties for the treatment of injured tissues is challenging due to the tradeoff between material stiffness and toughness while maintaining adherence to wet tissue surfaces. In most cases, bioadhesives with improved mechanical strength often lack an appropriate elastic compliance, hindering their application for sealing soft, elastic, and dynamic tissues. Here, we present a novel strategy for engineering tissue adhesives in which molecular building blocks are manipulated to allow for precise control and optimization of the various aforementioned properties without any tradeoffs. To introduce tunable mechanical properties and robust tissue adhesion, the hydrogel network presents different modes of covalent and noncovalent interactions using N-hydroxysuccinimide ester (NHS) conjugated alginate (Alg-NHS), poly (ethylene glycol) diacrylate (PEGDA), tannic acid (TA), and Fe^(3+) ions. Through combining and tuning different molecular interactions and a variety of crosslinking mechanisms, we were able to design an extremely elastic (924%) and tough (4697 kJ/m3) multifunctional hydrogel that could quickly adhere to wet tissue surfaces within 5 s of gentle pressing and deform to support physiological tissue function over time under wet conditions. While Alg-NHS provides covalent bonding with the tissue surfaces, the catechol moieties of TA molecules synergistically adopt a mussel-inspired adhesive mechanism to establish robust adherence to the wet tissue. The strong adhesion of the engineered bioadhesive patch is showcased by its application to rabbit conjunctiva and porcine cornea. Meanwhile, the engineered bioadhesive demonstrated painless detachable characteristics and in vitro biocompatibility. Additionally, due to the molecular interactions between TA and Fe3+, antioxidant and antibacterial properties required to support the wound healing pathways were also highlighted. Overall, by tuning various molecular interactions, we were able to develop a single-hydrogel platform with an “all-in-one” multifunctionality that can address current challenges of engineering hydrogel-based bioadhesives for tissue repair and sealing.

Biosynthesis of 4-hydroxyphenylpyruvic acid from L-tyrosine using recombinant Escherichia coli cells expressing membrane bound L-amino acid deaminase

4-Hydroxyphenylpyruvic acid （4-HPPA）, a kind of α-keto acid, is an intermediate in the metabolism of tyrosine and has a wide range of application in food, pharmaceutical and chemical industry. Using amino acids as raw material to prod uce the corresponding α-keto acid is thought to be both economic and efficient. Among the enzymes that convert amino acid to α-keto acid, membrane bound L-amino acid deaminase （mL-AAD）, which is anchored to the outer side of the cytomembrane, becomes an ideal enzyme to prepare α-keto acid since there is no cofactors needed and H2O2 production during the reaction. In this study, the mL-AAD from Proteus vulgaris was used to prepare whole-cell catalysts to produce 4-HPPA from L-tyrosine. The secretory efficiency of mL-AAD conducted by its own twin-arginine signal peptide （twin-arginine translocation pathway, Tat） and integrated pelB （the general secretory pathway, Sec）-Tat signal peptide was determined and compared firstly, using two pET systems （pET28a and pET20b）. It was found that the Tat pathway （pET28a-mlaad） resulted in higher cell-associated mL-AAD activity and cell biomass, and was more beneficial to prepare biocatalyst. In addition, expression hosts BI21 （DE3） and 0.05 mmol. L- 1 IPTG were found to be suitable for mL-AAD expression. The reaction conditions for mL-AAD were optimized and 72.72 mmol,L 1 4-HPPA was obtained from 100 mmol.L 1 tyrosine in 10 h under the optimized conditions. This bioprocess, which is more eco-friendly and economical than the traditional chemical synthesis ways, has great potential for industrial application.

Recent strategies for constructing efficient interfacial solar evaporation systems

Interfacial solar evaporation(ISE)is a promising technology to relieve worldwide freshwater shortages owing to its high energy conversion efficiency and environmentally sustainable potential.So far,many innovative materials and evaporators have been proposed and applied in ISE to enable highly controllable and efficient solar-to-thermal energy conversion.With rational design,solar evaporators can achieve excellent energy management for lowering energy loss,harvesting extra energy,and efficiently utilizing energy in the system to improve freshwater production.Beyond that,a strategy of reducing water vaporization enthalpy by introducing molecular engineering for water-state regulation has also been demonstrated as an effective approach to boost ISE.Based on these,this article discusses the energy nexus in two-dimensional(2D)and three-dimensional(3D)evaporators separately and reviews the strategies for design and fabrication of highly efficient ISE systems.The summarized work offers significant perspectives for guiding the future design of ISE systems with efficient energy management,which pave pathways for practical applications.

Development of organic redox-active materials in aqueous flow batteries: Current strategies and future perspectives

Aqueous redox flow batteries,by using redox-active molecules dissolved in nonflammable water solutions as electrolytes,are a promising technology for grid-scale energy storage.Organic redox-active materials offer a new opportunity for the construction of advanced flow batteries due to their advantages of potentially low cost,extensive structural diversity,tunable electrochemical properties,and high natural abundance.In this review,we present the emergence and development of organic redox-active materials for aqueous organic redox flow batteries(AORFBs),in particular,molecular engineering concepts and strategies of organic redox-active molecules.The typical design strategies based on organic redox species for high-capacity,high-stability,and high-voltage AORFBs are outlined and discussed.Molecular engineering of organic redox-active molecules for high aqueous solubility,high chemical/electrochemical stability,and multiple electron numbers as well as satisfactory redox potential gap between the redox pair is essential to realizing high-performance AORFBs.Beyond molecular engineering,the redoxtargeting strategy is an effective way to obtain high-capacity AORFBs.We further discuss and analyze the redox reaction mechanisms of organic redox species based on a series of electrochemical and spectroscopic approaches,and succinctly summarize the capacity degradation mechanisms of AORFBs.Furthermore,the current challenges,opportunities,and future directions of organic redox-active materials for AORFBs are presented in detail.