Fabrication of Supramolecular Bioactive Surfaces via β-Cyclodextrin-Based Host-Guest Interactions

Thermodynamic Reversal and Structural Correlation of 24-Crown-8/Protonated Tryptophan and 24-Crown 8/Protonated Serine Noncovalent Complexes in the Gas Phase vs in Solution: Quantum Chemical Analysis

We investigate the structures of 24-crown-8/H+/l-tryptophan (CR/TrpH+) and 24-crown-8/H+/l-serine (CR/SerH+) noncovalent host-guest complex both in the gas phase and in an aqueous solution by quantum chemical methods. The Gibbs free energies of the complex in the two phases are calculated to determine the thermodynamically most favorable conformer in each phase. Our predictions indicate that both the carboxyl and the ammonium in CR/TrpH+ and the ammonium in the CR/SerH+ complexes in the lowest Gibbs free energy configurations form hydrogen bonds (H-bonds) with the CR host in the gas phase, while the conformer with the "naked" (devoid of H-bond with the CR host) -CO2H (and/or -OH) is much less favorable (Gibbs free energy higher by >3.6 kcal/mol). In the solution phase, however, a "thermodynamic reversal" occurs, making the higher Gibbs free energy gas-phase CR/TrpH+ and CR/SerH+ conformers thermodynamically more favorable under the influence of solvent molecules. Consequently, the global minimum Gibbs free energy structure in solution is structurally correlated with the thermodynamically much less gas-phase conformer. Discussions are provided concerning the possibility of elucidating host-guest-solvent interactions in solution from the gas-phase host-guest configurations in molecular detail.

Simultaneous Rosiglitazone Release and Low-Density Lipoprotein Removal by Chondroitin Sodium Sulfate/Cyclodextrin/Poly(acrylic acid) Composite Adsorbents for Atherosclerosis Therapy

Atherosclerosis (AS) is characterized by the accumulation of substantial low-density lipoprotein (LDL) and inflammatory response. Hemoperfusion is commonly employed for the selective removal of LDL from the body. However, conventional hemoperfusion merely focuses on LDL removal and does not address the symptom of plaque associated with AS. Based on the LDL binding properties of acrylated chondroitin sodium sulfate (CSA), acrylated beta-cyclodextrin (CD) and acrylic acid (AA), along with the anti-inflammatory property of rosiglitazone (R), the fabricated AA-CSA-CD-R microspheres could simultaneously release R and facilitate LDL removal for hemoperfusion. The AA and CSA offer electrostatic adsorption sites for LDL, while the CD provides hydrophobic adsorption sites for LDL and weak binding sites for R. According to the Sips model, the maximum static LDL adsorption capacity of AA-CSA-CD-R is determined to be 614.73 mg/g. In dynamic simulated perfusion experiments, AA-CSA-CD-R exhibits an initial cycle LDL adsorption capacity of 150.97 mg/g. The study suggests that the weakened inflammatory response favors plaque stabilization. The anti-inflammatory property of the microspheres is verified through an inflammation model, wherein the microsphere extracts are cocultured with mouse macrophages. Both qualitative analysis of iNOS\TNF-α and quantitative analysis of IL-6\TNF-α collectively demonstrate the remarkable anti-inflammatory effect of the microspheres. Therefore, the current study presents a novel blood purification treatment of eliminating pathogenic factors and introducing therapeutic factors to stabilize AS plaque.

Influence of Surface Chemistry on Host/Guest Interactions: A Model Study on Redox-Sensitive β-Cyclodextrin/Ferrocene Complexes

While host/guest interactions are widely used to control molecular assembly on surfaces, quantitative information on the effect of surface chemistry on their efficiency is lacking. To address this question, we combined electrochemical characterization with quartz crystal microbalance with dissipation monitoring to study host/guest interactions between surface-attached ferrocene (Fc) guests and soluble β-cyclodextrin (β-CD) hosts. We identified several parameters that influence the redox response, β-CD complexation ability, and repellent properties of Fc monolayers, including the method of Fc grafting, the linker connecting Fc with the surface, and the diluting molecule used to tune Fc surface density. The study on monovalent β-CD/Fc complexation was completed by the characterization of multivalent interactions between Fc monolayers and β-CD-functionalized polymers, with new insights being obtained on the interplay between the surface chemistry, binding efficiency, and reversibility under electrochemical stimulus. These results should facilitate the design of well-defined functional interfaces and their implementation in stimuli-responsive materials and sensing devices.

Selective Perchlorate Sensing Using Electrochemical Impedance Spectroscopy with Self-Assembled Monolayers of semiaza-Bambusurils

In the last two decades, perchlorate salts have been identified as environmental pollutants and recognized as potential substances affecting human health. We describe self-assembled monolayers (SAMs) of novel semiaza-bambus[6]urils (semiaza-BUs) equipped with thioethers or disulfide (dithiolane) functionalities as surface-anchoring groups on gold electrodes. Cyclic voltammetry (CV) with Fe(CN)6 3-/4- as a redox probe, together with X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and ellipsometry, were employed to characterize the interactions at the interface between the anchoring groups and the metal substrate. Data showed that the anion receptors' packing on the gold strongly depends on the anchoring group. As a result, SAMs of BUs with lipoic amide side chains show a concentration-dependent layer thickness. The BU SAMs are extremely stable on repeated electrochemical potential scans and can selectively recognize perchlorate anions. Our electrochemical impedance spectroscopy (EIS) studies indicated that semiaza-BU equipped with the lipoic amide side chains binds perchlorate (2-100 mM) preferentially over other anions such as F- , Cl- , I- , AcO- , H2 PO4 - , HPO4 2- , SO4 2- , NO2 - , NO3 - , or CO3 2- . The resistance performance is 10 to 100 times more efficient than SAMs containing all other tested anions.

Enhanced Intracellular Delivery and Cell Harvest Using a Candle Soot-Based Photothermal Platform with Dual-Stimulus Responsiveness

Intracellular delivery of bioactive macromolecules and functional materials plays a crucial role in fundamental biological research and clinical applications. Nondestructive and efficient harvesting of engineered cells is also required for some specific applications. In this work, we develop a multifunctional platform based on candle soot modified with copolymer brushes containing temperature-responsive poly(N-isopropylacrylamide) (PNIPAAm) and sugar-responsive phenylboronic acid (PBA) components. This platform possesses a high cell adhesion capacity due to the inherent hierarchical structure of candle soot and the formation of boronate ester bonds between the PBA groups and glycoproteins on the cell membrane. Under the irradiation of a near-infrared laser, the excellent light-to-heat conversion ability of candle soot enables the highly efficient delivery of macromolecules into diverse cells (including hard-to-transfect cells) attached to the surface via a photothermal-poration mechanism. Owing to the temperature-responsive properties of PNIPAAm and the sugar-responsive properties of PBA, the engineered cells could be harvested nondestructively from the platform by a mild treatment using a cold fructose solution. A proof-of-concept experiment demonstrates that fibroblasts attached to the surface could be transfected by a functional plasmid encoding basic fibroblast growth factor and then harvested efficiently and recultured with improved proliferation and migration ability. The whole delivery-harvesting process required less than 1 h, allowing the cells to be engineered without compromising their viability. This platform thus provides a widely applicable method for both the intracellular delivery of diverse macromolecules efficiently as well as harvesting engineered cells simply and safely, holding great potential for biomedical applications.

Interfacial Rheological and Emulsion Properties of Self-Assembled Cyclodextrin-Oil Inclusion Complexes

To investigate the effect of the molecular size of alkanes and the cavity size of cyclodextrins (CDs) on the formation of interfacial host-guest inclusion complexes, the interfacial tension (IFT) of CD (α-CD, β-CD, γ-CD) solutions against oils (hexadecane, dodecylbenzene) was determined by interfacial dilational rheology measurements. The results show that the "space compatibility" between CDs and oil molecules is crucial for the formation of interface host-guest inclusion complexes. Hexadecane with a smaller molecular size can form host-guest inclusion complexes with small cavities of α-CD and β-CD, dodecylbenzene with a larger molecular size can form interfacial aggregates with the medium-sized cavity of β-CD easily, and the polycyclic aromatic hydrocarbon molecules in kerosene can form inclusion complexes with the large cavity of γ-CD. The formation of interfacial inclusion complexes leads to lower IFT values, higher interfacial dilational modulus, nonlinear IFT responses to the interface area oscillating, and skin-like films at the oil-water interface. What's more, the phase behavior of Pickering emulsions formed by CDs with different oils is explored, and the phenomena in alkane-CD emulsions are in line with the results in dilatation rheology. The interfacial active host-guest structure in the kerosene-γ-CD system improves the stability of the Pickering emulsion, which results in smaller emulsion droplets. This unique space compatibility characteristic is of great significance for the application of CDs in selective host-guest recognition, sensors, enhanced oil recovery, food industries, and local drug delivery.

Multistage Anticoagulant Surfaces: A Synergistic Combination of Protein Resistance, Fibrinolysis, and Endothelialization

Anticoagulant surface modification of blood-contacting materials has been shown to be effective in preventing thrombosis and reducing the dose of anticoagulant drugs that patients take. However, commercially available anticoagulant coatings, that is, both bioinert and bioactive coatings, are typically based on a single anticoagulation strategy. This puts the anticoagulation function of the coating at risk of failure during long-term use. Considering the several pathways of the human coagulation system, the synergy of multiple anticoagulation theories may provide separate, targeted effects at different stages of thrombosis. Based on this presumption, in this work, negatively charged poly(sodium p-styrenesulfonate-co-oligo(ethylene glycol) methyl ether methacrylate) and positively charged poly(lysine-co-1-adamantan-1-ylmethyl methacrylate) were synthesized to construct matrix layers on the substrate by electrostatic layer-by-layer self-assembly (LBL). Amino-functionalized β-cyclodextrin (β-CD-PEI) was subsequently immobilized on the surface by host-guest interactions, and heparin was grafted. By adjusting the content of poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA), the interactions between modified surfaces and plasma proteins/cells were regulated. This multistage anticoagulant surface exhibits inertness at the initial stage of implantation, resisting nonspecific protein adsorption (POEGMA). When coagulation reactions occur, heparin exerts its active anticoagulant function in a timely manner, blocking the pathway of thrombosis. If thrombus formation is inevitable, lysine can play a fibrinolytic role in dissolving fibrin clots. Finally, during implantation, endothelial cells continue to adhere and proliferate on the surface, forming an endothelial layer, which meets the blood compatibility requirements. This method provides a new approach to construct a multistage anticoagulant surface for blood-contacting materials.

Enzymatic Self-Assembly of Adamantane-Peptide Conjugate for Combating Staphylococcus aureus Infection

Staphylococcus aureus (S. aureus) remains a leading cause of bacterial infections. However, eradication of S. aureus infections with common antibiotics is increasingly difficult due to outbreaks of drug resistance. Therefore, new antibiotic classes and antibacterial strategies are urgently in demand. Herein, it is shown that an adamantane-peptide conjugate, upon dephosphorylation by alkaline phosphatase (ALP) constitutively expressed on S. aureus, generates fibrous assemblies in situ to combat S. aureus infection. By attaching adamantane to a phosphorylated tetrapeptide Nap-Phe-Phe-Lys-Tyr(H2 PO3 )-OH, the rationally designed adamantane-peptide conjugate Nap-Phe-Phe-Lys(Ada)-Tyr(H2 PO3 )-OH (Nap-FYp-Ada) is obtained. Upon bacterial ALP activation, Nap-FYp-Ada is dephosphorylated and self-assembles into nanofibers on the surface of S. aureus. As revealed by cell assays, the assemblies of adamantane-peptide conjugates interact with cell lipid membrane and thereby disrupt membrane integrity to kill S. aureus. Animal experiments further demonstrate the excellent potential of Nap-FYp-Ada in the treatment of S. aureus infection in vivo. This work provides an alternative approach to design antimicrobial agents.

DNA-based assemblies with bischromophoric styryl dye-chromene conjugates and cucurbit[7]uril

Novel conjugates consist of 4-styrylpyridinium dye and 2,2-diphenyl-2H-chromene moiety were obtained, and their affinity to double stranded DNA and cucurbit[7]uril was investigated. With a combination of absorption, fluorescence and circular dichroism spectroscopies as well as MALDI-TOF mass spectrometry, we demonstrate that these compounds can interact with macromolecules to form of the supramolecular assemblies due to two suitable binding sites. The ternary complex is formed as a result of the intercalation of a positively charged styryl part between DNA base pairs, while cucurbit[7]uril is located on the alkyl chain between two moieties of conjugate. All these findings provide valuable information into controlling the interaction between organic molecules, DNA and cucurbit[7]uril.

The Effect of Alkali Iodide Salts in the Inclusion Process of Phenolphthalein in β-Cyclodextrin: A Spectroscopic and Theoretical Study

The formation of the inclusion complex between β-cyclodextrin (CD) and phenolphthalein (PP) was investigated by means of UV-Vis and FT-IR spectroscopies. The thermodynamic parameters were calculated in the absence and presence of LiI, KI, NaI and CsI iodide salts. The enthalpy change during the formation was found to be negative for all solutions with iodide salts. The enthalpy change was found to decrease in the sequence no salt > NaI > KI> CsI > LiI. Moreover, it was observed that with increasing salt concentration enthalpy decreases monotonically. The interaction between the two molecules was mostly attributed to hydrogen bonding and Van der Waals interactions. Thermodynamic properties revealed that electrostatic forces also contribute when LiI is present in solutions. A molecular docking study was performed to elucidate the docking between phenolphthalein and cyclodextrin. The FT-IR spectra of CD, PP and the CD-PP complex were recorded to establish the formation of the inclusion complex. Semi-empirical and DFT methods were utilized to study theoretically the complexation process and calculate the IR vibrational spectra. The adequate agreement between theoretical and experimental results supports the proposed structural model for the CD-PP complexation.

da Silva VA, S. da Silva GF, Santos ECS, de S. Baêta E, Brant de Campos J, Carvalho NMF, Malta LFB, Senra JD. Mild and Rapid Light-Driven Suzuki-Miyaura Reactions Catalyzed by AuPd Nanoparticles in Water at Room Temperature

Organic reactions carried out in water under mild conditions are state-of-the-art in terms of environmentally benign chemical processes. In this direction, plasmonic catalysis can aid in accomplishing such tasks. In the present work, cyclodextrin-mediated AuPd bimetallic nanoparticles (NPs) were applied in room-temperature aqueous Suzuki-Miyaura reactions aiming at preparing biaryl products based on fluorene, isatin, benzimidazole and resorcinol, with yields of 77 % up to 95 %. AuPd NPs were revealed to be a physical mixture of Au and Pd particles circa 20 and 2 nm, respectively, through X-ray diffraction, dynamic light scattering, UV-Vis spectroscopy and transmission electron microscopy analyses.

Non-Covalent Interaction on the Self-Healing of Mechanical Properties in Supramolecular Polymers

Supramolecular polymers are widely utilized and applied in self-assembly or self-healing materials, which can be repaired when damaged. Normally, the healing process is classified into two types, including extrinsic and intrinsic self-healable materials. Therefore, the aim of this work is to review the intrinsic self-healing strategy based on supramolecular interaction or non-covalent interaction and molecular recognition to obtain the improvement of mechanical properties. In this review, we introduce the main background of non-covalent interaction, which consists of the metal–ligand coordination, hydrogen bonding, π–π interaction, electrostatic interaction, dipole–dipole interaction, and host–guest interactions, respectively. From the perspective of mechanical properties, these interactions act as transient crosslinking points to both prevent and repair the broken polymer chains. For material utilization in terms of self-healing products, this knowledge can be applied and developed to increase the lifetime of the products, causing rapid healing and reducing accidents and maintenance costs. Therefore, the self-healing materials using supramolecular polymers or non-covalent interaction provides a novel strategy to enhance the mechanical properties of materials causing the extended cycling lifetime of products before replacement with a new one.

Unveiling host-guest-solvent interactions in solution by identifying highly unstable host-guest configurations in thermal non-equilibrium gas phase

We propose a novel scheme of examining the host-guest-solvent interactions in solution from their gas phase structures. By adopting the permethylated β-cyclodextrin (perm β-CD)-protonated L-Lysine non-covalent complex as a prototypical system, we present the infrared multiple photon dissociation (IRMPD) spectrum of the gas phase complex produced by electrospray ionization technique. In order to elucidate the structure of perm β-CD)/LysH⁺ complex in the gas phase, we carry out quantum chemical calculations to assign the two strong peaks at 3,340 and 3,560 cm^-1 in the IRMPD spectrum, finding that the carboxyl forms loose hydrogen bonding with the perm β-CD, whereas the ammonium group of L-Lysine is away from the perm β-CD unit. By simulating the structures of perm β-CD/H⁺/L-Lysine complex in solution using the supramolecule/continuum model, we find that the extremely unstable gas phase structure corresponds to the most stable conformer in solution.

Ionic interaction-driven switchable bactericidal surfaces

Bacteria in the external environment inevitably invade the wound and subsequently colonize the wound surface during surgery and biomedical operations, which slows down the process of wound healing and tissue repair; this poses a significant threat to human health. Therefore, the development of an intelligent antibacterial surface has become the focus of research in the field of antimicrobial strategies, which has important social and economic significance. Here, we present a simple approach of producing an ionic interaction-driven anionic activation substratum which is then functionalized with cationic molecules through coulombic interactional immobilization. The switchable multifunctional antibacterial surface can decrease bacterial attachment and inactivate the attached microorganisms, thus overcoming the conventional challenge for antibacterial surfaces. Briefly, poly (3-sulfopropyl methacrylate potassium salt) (PSPMA) brushes were constructed by surface-initiated atom transfer radical polymerization on silicon or cotton fabric substrates, and a positive-charged component, namely lysozyme (LYZ), hexadecyl trimethyl ammonium bromide (CTAB) or chitosan (CS), was loaded on negative-charged sulfonate groups through electrostatic interactions. The resultant brush-grafted surfaces exhibited more than ∼95.5% bactericidal efficacy and ∼92.8% release rate after the introduction of an adequate amount of contra-ions (1.0 M; Na⁺ & Cl^-) against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, thus achieving a regenerated surface through the cyclic process of "assembly-dissociation". Smart cotton fabric (Fabric-PSPMA/LYZ and Fabric-PSPMA/CS) surfaces were constructed, which were found to promote wound epidermal tissue regeneration with a higher efficiency after 7-day in vivo studies. This ionic interaction-driven method used in the present work is simple and can reversibly renew antibacterial surfaces, which will help in the wider utilization of switchable antibacterial materials with a more ecologic and economic significance. STATEMENT OF SIGNIFICANCE: Smart antibacterial surfaces with renewable characteristics have attracted considerable interests over the past few years. Here, we used ionic interaction-driven force to manipulate dynamic conformational changes in PSPMA surface brushes, accompanied by highly switchable bacteria killing and bacteria releasing behaviors. Different cationic molecules were also designed for assembly/dissociation on the PSPMA-modified surfaces, and the essential parameters, including chemical structures, molecular weight, and cationic charge density, were investigated. With the refined structural combinations and the balance of bacteria killing/bacteria releasing behaviors, smart cotton fabrics (e.g., Fabric-PSPMA/lysozyme and Fabric-PSPMA/chitosan) were designed that could promote wound healing and tissue repair. These results contribute to the fundamental understanding of a switchable cationic-anionic pair design and the corresponding practical, renewable, highly antibacterial fabric.

Tunable arrangement of hydrogel and cyclodextrin-based metal organic frameworks suitable for drug encapsulation and release

The present study focused on the integration of beta-cyclodextrin based metal-organic frameworks (β-CDMOF) with polymer to obtain hybrid materials with advantageous properties compared to traditional single-component polymers or metal-organic frameworks (MOF) matrixes. We fabricated two complexes with different morphology and structure. During the in situ growth of β-CDMOF around the hydrogel, potassium ions on polysaccharides gradually dissociated to participate in the growth of crystals, while other potassium ions on the carboxylic acid groups provided bridges between crystals and hydrogel, forming a necklace-shaped complex (SHPs@β-CDMOF). Hydrogen bonding and coordination interactions between β-CDMOF and hydrogel are present in a dendritic sandwich-shaped complex (β-CDMOF@SHPs). Furthermore, using the hydrophobic molecule curcumin as a model drug, we have demonstrated that SHPs@β-CDMOF and β-CDMOF@SHPs hybrid materials stabilize the included drug and have potential for controlled drug release. Collectively, the integration of MOF with polymer holds a great promise for drug delivery applications.

Fabrication of Host-Guest Complexes between Adamantane-Functionalized 1,3,4-Oxadiazoles and β-Cyclodextrin with Improved Control Efficiency against Intractable Plant Bacterial Diseases

Supramolecular chemistry provides huge potentials and opportunities in agricultural pest management. In an attempt to develop highly bioactive, eco-friendly, and biocompatible supramolecular complexes for managing intractable plant bacterial diseases, herein, a type of interesting adamantane-functionalized 1,3,4-oxadiazole was rationally prepared to facilitate the formation of supramolecular complexes via β-cyclodextrin-adamantane host-guest interactions. Initial antibacterial screening revealed that most of these adamantane-decorated 1,3,4-oxadiazoles were obviously bioactive against three typically destructive phytopathogens. The lowest EC₅₀ values could reach 0.936 (III₁₈), 0.889 (III₁₈), and 2.10 (III₁₉) μg/mL against the corresponding Xanthomonas oryzae pv. oryzae (Xoo), Xanthomonas axonopodis pv. citri (Xac), and Pseudomonas syringae pv. actinidiae (Psa). Next, the representative supramolecular binary complex III₁₈@β-CD (binding mode 1:1) was successfully fabricated and characterized by ¹H nuclear magnetic resonance (NMR), isothermal titration calorimetry (ITC), high-resolution mass spectrometry (HRMS), dynamic light scattering (DLS), and transmission electron microscopy (TEM). Eventually, correlative water solubility and foliar surface wettability were significantly improved after the formation of host-guest assemblies. In vivo antibacterial evaluation found that the achieved supramolecular complex could distinctly alleviate the disease symptoms and promote the control efficiencies against rice bacterial blight (from 34.6-35.7% (III₁₈) to 40.3-43.6% (III₁₈@β-CD)) and kiwi canker diseases (from 41.0-42.3% (III₁₈) to 53.9-68.0% (III₁₈@β-CD)) at 200 μg/mL (active ingredient). The current study can provide a feasible platform and insight for constructing biocompatible supramolecular assemblies for managing destructive bacterial infections in agriculture.

Detection of aliphatic aldehydes by a pillar[5]arene-based fluorescent supramolecular polymer with vaporchromic behavior

The detection of volatile aliphatic aldehydes is of significance because of their chemical toxicity, physical volatility and widespread applications in chemical industrial processes. In this work, the direct detection of aliphatic aldehydes is tackled using a fluorescent supramolecular polymer with vaporchromic behavior which is contructed by pillar[5]arene-based host-guest intereactions. Thin films with strong orange-yellow fluorescence are prepared by coating the linear supramolecular polymer on glass sheets. When the thin films are exposed to aliphatic aldehydes with different carbon chain lengths, they can selectivly sensing  n -butyraldehyde ( C 4 ) and caprylicaldehyde ( C 8 ), accompanied by fluorescence quenching, indicating that the supramolecular polymer is a highly selective vapochromic response material for aliphatic aldehydes with long alkyl chains.

Melittin-Based Nano-Delivery Systems for Cancer Therapy

Melittin (MEL) is a 26-amino acid polypeptide with a variety of pharmacological and toxicological effects, which include strong surface activity on cell lipid membranes, hemolytic activity, and potential anti-tumor properties. However, the clinical application of melittin is restricted due to its severe hemolytic activity. Different nanocarrier systems have been developed to achieve stable loading, side effects shielding, and tumor-targeted delivery, such as liposomes, cationic polymers, lipodisks, etc. In addition, MEL can be modified on nano drugs as a non-selective cytolytic peptide to enhance cellular uptake and endosomal/lysosomal escape. In this review, we discuss recent advances in MEL’s nano-delivery systems and MEL-modified nano drug carriers for cancer therapy.

Recent advances in chiral discrimination on host-guest functionalized interfaces

Chiral discrimination has gained much focus in supramolecular chemistry, since it is one of the fundamental processes in biological systems, enantiomeric separation and biochemical sensors. Though most of the biochemical processes can routinely recognize biological enantiomers, enantioselective identification of chiral molecules in artificial systems is currently one of the challenging topics in the field of chiral discrimination. Inaccuracy, low separation efficiency and expensive instrumentation were considered typical problems in artificial systems. Recently, chiral recognition on the interfaces has been widely used in the fields of electrochemical detection and biochemical sensing. For the moment, a series of macrocyclic host functionalized interfaces have been developed for use as chiral catalysts or for enantiomeric separation. Here, we have briefly exposited the most recent advances in the fabrication of supramolecular functionalized interfaces and their application for chiral recognition.

Advances in Application of Azobenzene as a Trigger in Biomedicine: Molecular Design and Spontaneous Assembly

Azobenzene is a well-known derivative of stimulus-responsive molecular switches and has shown superior performance as a functional material in biomedical applications. The results of multiple studies have led to the development of light/hypoxia-responsive azobenzene for biomedical use. In recent years, long-wavelength-responsive azobenzene has been developed. Matching the longer wavelength absorption and hypoxia-response characteristics of the azobenzene switch unit to the bio-optical window results in a large and effective stimulus response. In addition, azobenzene has been used as a hypoxia-sensitive connector via biological cleavage under appropriate stimulus conditions. This has resulted in on/off state switching of properties such as pharmacology and fluorescence activity. Herein, recent advances in the design and fabrication of azobenzene as a trigger in biomedicine are summarized.

Macroscopic Supramolecular Assembly Strategy to Construct 3D Biocompatible Microenvironments with Site-Selective Cell Adhesion

Three-dimensional (3D) scaffolds with chemical diversity are significant to direct cell adhesion onto targeted surfaces, which provides solutions to further control over cell fates and even tissue formation. However, the site-specific modification of specific biomolecules to realize selective cell adhesion has been a challenge with the current methods when building 3D scaffolds. Conventional methods of immersing as-prepared structures in solutions of biomolecules lead to nonselective adsorption; recent printing methods have to address the problem of switching multiple nozzles containing different biomolecules. The recently developed concept of macroscopic supramolecular assembly (MSA) based on the idea of "modular assembly" is promising to fabricate such 3D scaffolds with advantages of flexible design and combination of diverse modules with different surface chemistry. Herein we report an MSA method to fabricate 3D ordered structures with internal chemical diversity for site-selective cell adhesion. The 3D structure is prepared via 3D alignment of polydimethylsiloxane (PDMS) building blocks with magnetic pick-and-place operation and subsequent interfacial bindings between PDMS based on host/guest molecular recognition. The site-specific cell affinity is realized by distributing targeted building blocks that are modified with polylysine molecules of opposite chiralities: PDMS modified with films containing poly-l-lysine (PLL) show higher cell density than those with poly-d-lysine (PDL). This principle of selective cell adhesion directed simply by spatial distribution of chiral molecules has been proven effective for five different cell lines. This facile MSA strategy holds promise to build complex 3D microenvironment with on-demand chemical/biological diversities, which is meaningful to study cell/material interactions and even tissue formation.

High-throughput screening and rational design of biofunctionalized surfaces with optimized biocompatibility and antimicrobial activity

Peptides are widely used for surface modification to develop improved implants, such as cell adhesion RGD peptide and antimicrobial peptide (AMP). However, it is a daunting challenge to identify an optimized condition with the two peptides showing their intended activities and the parameters for reaching such a condition. Herein, we develop a high-throughput strategy, preparing titanium (Ti) surfaces with a gradient in peptide density by click reaction as a platform, to screen the positions with desired functions. Such positions are corresponding to optimized molecular parameters (peptide densities/ratios) and associated preparation parameters (reaction times/reactant concentrations). These parameters are then extracted to prepare nongradient mono- and dual-peptide functionalized Ti surfaces with desired biocompatibility or/and antimicrobial activity in vitro and in vivo. We also demonstrate this strategy could be extended to other materials. Here, we show that the high-throughput versatile strategy holds great promise for rational design and preparation of functional biomaterial surfaces.

Host-Guest Interaction-Mediated Photo/Temperature Dual-Controlled Antibacterial Surfaces

Development of smart switchable surfaces to solve the inevitable bacteria attachment and colonization has attracted much attention; however, it proves very challenging to achieve on-demand regeneration for noncontaminated surfaces. We herein report a smart, host-guest interaction-mediated photo/temperature dual-controlled antibacterial surface, topologically combining stimuli-responsive polymers with nanobactericide. From the point of view of long-chain polymer design, the peculiar hydration layer generated by hydrophilic poly(2-hydroxyethyl methacrylate) (polyHEMA) segments severs the route of initial bacterial attachment and subsequent proliferation, while the synergistic effect on chain conformation transformation poly(N-isopropylacrylamide) (polyNIPAM) and guest complex dissociation azobenzene/cyclodextrin (Azo/CD) complex greatly promotes the on-demand bacterial release in response to the switch of temperature and UV light. Therefore, the resulting surface exhibits triple successive antimicrobial functions simultaneously: (i) resists ∼84.9% of initial bacterial attachment, (ii) kills ∼93.2% of inevitable bacteria attack, and (iii) releases over 94.9% of killed bacteria even after three cycles. The detailed results not only present a potential and promising strategy to develop renewable antibacterial surfaces with successive antimicrobial functions but also contribute a new antimicrobial platform to biomedical or surgical applications.

Facile construction of noncovalent graft copolymers with triple stimuli-responsiveness for triggered drug delivery

A triple stimuli-responsive noncovalent graft copolymer was designed and synthesized by the host–guest interactions between β-CD grafted dextran and ferrocene-terminated poly(lactide).

Cyclodextrin-Based Functional Glyconanomaterials

Cyclodextrins (CDs) have long occupied a prominent position in most pharmaceutical laboratories as "off-the-shelve" tools to manipulate the pharmacokinetics of a broad range of active principles, due to their unique combination of biocompatibility and inclusion abilities. The development of precision chemical methods for their selective functionalization, in combination with "click" multiconjugation procedures, have further leveraged the nanoscaffold nature of these oligosaccharides, creating a direct link between the glyco and the nano worlds. CDs have greatly contributed to understand and exploit the interactions between multivalent glycodisplays and carbohydrate-binding proteins (lectins) and to improve the drug-loading and functional properties of nanomaterials through host-guest strategies. The whole range of capabilities can be enabled through self-assembly, template-assisted assembly or covalent connection of CD/glycan building blocks. This review discusses the advancements made in this field during the last decade and the amazing variety of functional glyconanomaterials empowered by the versatility of the CD component.

Antifouling Nanofiltration Membrane Fabrication via Surface Assembling Light-Responsive and Regenerable Functional Layer

Membrane fouling, caused by aggregation of organics and microorganisms from filtrate on the membrane surface, seriously reduces the service life of a nanofiltration (NF) membrane. Developing facile and renewable antifouling modification methods without sacrificing separation properties of the membrane remain an imperative requirement. Herein, a thin-film composite (TFC) NF membrane with a light-responsive and regenerable functional layer (P-TFC) was fabricated via host-guest interactions between the azobenzene (guest) labeled functional polymers and the β-cyclodextrin (host) bonded membrane surface (H-TFC). The P-TFC-3 not only showed outstanding antifouling ability and high flux recovery ratio (FRR > 90% at the fourth antiadhesive test) but also exhibited enhanced water permeability (17.9 L m^-2 h^-1 bar^-1) and high selectivity (α_MgSO4^NaCl = 33.4 and fast antibiotics enrichment capacity) compared with the pristine membrane. Furthermore, when the functional layer was contaminated, it can be removed by ultraviolet light irradiation and a new functional layer can be rebuilt by adding fresh azobenzene labeled functional polymers. After several regeneration processes, the membranes still showed constant separation properties and high flux recovery ability (FRR > 90%). This work proposes an easy-to-assemble and regenerable surface modification strategy to endow TFC NF membranes with excellent fouling resistance and sustainable utilization ability while maintaining high separation properties.

Glycan Nanobiosensors

This review paper comprehensively summarizes advances made in the design of glycan nanobiosensors using diverse forms of nanomaterials. In particular, the paper covers the application of gold nanoparticles, quantum dots, magnetic nanoparticles, carbon nanoparticles, hybrid types of nanoparticles, proteins as nanoscaffolds and various nanoscale-based approaches to designing such nanoscale probes. The article covers innovative immobilization strategies for the conjugation of glycans on nanoparticles. Summaries of the detection schemes applied, the analytes detected and the key operational characteristics of such nanobiosensors are provided in the form of tables for each particular type of nanomaterial.

Selection of Affinity Reagents to Neutralize the Hemolytic Toxicity of Melittin Based on a Self-Assembled Nanoparticle Library

Antibodies are the most common affinity reagents for specific target recognition. However, their applications are limited by high cost and low stability. Thus, seeking substitutes for antibodies is of great significance. In this work, we designed a library containing 82 self-assembled nanoparticles (SNPs) based on the self-assembly of β-cyclodextrin polymers and adamantane derivatives, and then screened out eight types of SNPs capable of suppressing the toxicity of melittin using a hemolytic activity neutralization assay. The affinities of the SNPs to melittin were demonstrated using surface plasmon resonance (SPR). As evidenced by cytotoxicity experiments, SNPs could also suppress the toxicity of melittin to other cells. In addition, to verify the universality of our method, 11 types of SNPs capable of neutralizing another toxic peptide, phenolic soluble polypeptide (PSMα3) secreted by Staphylococcus aureus, were selected from the same SNP library. Our self-assembly-based method for the library preparation has the advantages of flexible design, mild experimental condition, and simple operation, which is expected to seek artificial affinity reagents for more species.

Multistimulus Responsive Biointerfaces with Switchable Bioadhesion and Surface Functions

Stimuli-responsive biointerfaces can serve as dynamic tools for modulation of biointerfacial interactions. Considering the complexity of biological environments, surfaces with multistimulus responsive switchable bioactivity are of great interest. In the work reported herein, a multistimulus responsive biointerface with on-off switchable bioadhesion (protein adsorption, bacterial adhesion, and cell adhesion) and surface functions in response to change in temperature, pH, or sugar content is developed. This surface is based on a silicon modified with a copolymer containing a thermoresponsive component (poly(N-isopropylacrylamide)) and a component, phenylboronic acid, that can form pH-responsive and sugar-responsive dynamic boronate ester bonds with diol-containing molecules. It is shown that biointeractions including protein adsorption and release, bacteria and cell attachment and detachment on this surface can be regulated by changing temperature, pH, and sugar content of the medium, either individually or all three simultaneously. Furthermore, this surface can switch between two different functions, namely between killing and releasing bacteria, by introduction of a diol-containing biocidal compound. Compared to switchable surfaces that are responsive to only one stimulus, our multistimulus responsive surface is better adapted to respond to the multifunctional complexities of the biological environment and thus has potential for use in numerous biomedical and biotechnology applications.

Self-assembling morphology-tunable single-component supramolecular antibiotics for enhanced antibacterial manipulation

This single-component supramolecular antibiotic can undergo reversible self-assembling morphology transitions under sequential ultrasonic and redox stimuli. The self-assemblies with different morphologies display effective antibacterial regulation.

Design of salt-responsive and regenerative antibacterial polymer brushes with integrated bacterial resistance, killing, and release properties

The development of smart materials and surfaces with multiple antibacterial actions is of great importance for both fundamental research and practical applications, but this has proved to be extremely challenging. In this work, we proposed to integrate salt-responsive polyDVBAPS (poly(3-(dimethyl(4-vinylbenzyl) ammonio)propyl sulfonate)), antifouling polyHEAA (poly(N-hydroxyethyl acrylamide)), and bactericidal TCS (triclosan) into single surfaces by polymerizing and grafting polyDVBAPS and polyHEAA onto the substrate in a different way to form two types of polyDVBAPS/poly(HEAA-g-TCS) and poly(DVBAPS-b-HEAA-g-TCS) brushes with different hierarchical structures, as confirmed by X-ray photoelectron spectroscopy (XPS), atom force microscopy (AFM), and ellipsometry. Both types of polymer brushes demonstrated their tri-functional antibacterial activity to resist bacterial attachment by polyHEAA, to release ∼90% of dead bacteria from the surface by polyDVBAPS, and to kill ∼90% of bacteria on the surface by TCS. Comparative studies also showed that removal of any component from polyDVBAPS/poly(HEAA-g-TCS) and poly(DVBAPS-b-HEAA-g-TCS) compromised the overall antibacterial performance, further supporting a synergistic effect of the three compatible components. More importantly, the presence of salt-responsive polyDVBAPS allowed both brushes to regenerate with almost unaffected antibacterial capacity for reuse in multiple kill-and-release cycles. The tri-functional antibacterial surfaces present a promising design strategy for further developing next-generation antibacterial materials and coatings for antibacterial applications.

Reversible, High-Affinity Surface Capturing of Proteins Directed by Supramolecular Assembly

The ability to design surfaces with reversible, high-affinity protein binding sites represents a significant step forward in the advancement of analytical methods for diverse biochemical and biomedical applications. Herein, we report a dynamic supramolecular strategy to directly assemble proteins on surfaces based on multivalent host-guest interactions. The host-guest interactions are achieved by one-step nanofabrication of a well-oriented β-cyclodextrin host-derived self-assembled monolayer on gold (β-CD-SAM) that forms specific inclusion complexes with hydrophobic amino acids located on the surface of the protein. Cytochrome c, insulin, α-chymotrypsin, and RNase A are used as model guest proteins. Surface plasmon resonance and static time-of-flight secondary ion mass spectrometry studies demonstrate that all four proteins interact with the β-CD-SAM in a specific manner via the hydrophobic amino acids on the surface of the protein. The β-CD-SAMs bind the proteins with high nanomolar to single-digit micromolar dissociation constants ( K_D). Importantly, while the proteins can be captured with high affinity, their release from the surface can be achieved under very mild conditions. Our results expose the great advantages of using a supramolecular approach for controlling protein immobilization, in which the strategy described herein provides unprecedented opportunities to create advanced bioanalytic and biosensor technologies.

Responsive and Synergistic Antibacterial Coatings: Fighting against Bacteria in a Smart and Effective Way

Antibacterial coatings that eliminate initial bacterial attachment and prevent subsequent biofilm formation are essential in a number of applications, especially implanted medical devices. Although various approaches, including bacteria-repelling and bacteria-killing mechanisms, have been developed, none of them have been entirely successful due to their inherent drawbacks. In recent years, antibacterial coatings that are responsive to the bacterial microenvironment, that possess two or more killing mechanisms, or that have triggered-cleaning capability have emerged as promising solutions for bacterial infection and contamination problems. This review focuses on recent progress on three types of such responsive and synergistic antibacterial coatings, including i) self-defensive antibacterial coatings, which can "turn on" biocidal activity in response to a bacteria-containing microenvironment; ii) synergistic antibacterial coatings, which possess two or more killing mechanisms that interact synergistically to reinforce each other; and iii) smart "kill-and-release" antibacterial coatings, which can switch functionality between bacteria killing and bacteria releasing under a proper stimulus. The design principles and potential applications of these coatings are discussed and a brief perspective on remaining challenges and future research directions is presented.