Investigation of the Assembly Behavior of an Amphiphilic Lipopeptide at the Liquid Crystal-Aqueous Interface

Dual-Mechanism Glycolipidpeptide with High Antimicrobial Activity, Immunomodulatory Activity, and Potential Application for Combined Antibacterial Therapy

Bacterial drug resistance is becoming increasingly serious, and it is urgent to develop effective antibacterial drugs. Antimicrobial peptides (AMPs), as potential candidates against bacteria, have a broad prospect for development. Herein, a series of AMPs with biological characteristics (net positive charge, amphiphilicity, and α-helix), an AXA motif recognized by membrane bound serine protease type I signal peptidases (SPase I), an FLPII motif to reduce hemolysis, and a monosaccharide motif to improve the stability and activity were designed and synthesized, and among which, the glycolipidpeptide GLP6 (glycosylated LP6 lipopeptide) had excellent antibacterial and immunomodulatory activity, good stability and biocompatibility, and excellent biofilm eradication and membrane penetrating activity. The positively charged spherical aggregates formed by self-assembly of GLP6 could encapsulate tetracycline (TC) to form GLP6@TC with a sustained-release effect, which could enhance the sensitivity of bacteria to the antibiotic and realize combined sterilization. The results of acute peritonitis and bacterial keratitis showed that GLP6@TC had a good combined antibacterial effect and the ability to inhibit interleukin-2 (IL-2), which could significantly reduce the inflammatory response while treating bacterial infection, and it had great potential for application. The results of computer molecular docking showed the AXA motif could effectively bind to SPase I, which was consistent with the results of biological experiments. In general, the study could provide a perspective for the design of AMPs and combined antibacterial therapy.

Advanced Functional Liquid Crystals

Liquid crystals have been intensively studied as functional materials. Recently, integration of various disciplines has led to new directions in the design of functional liquid-crystalline materials in the fields of energy, water, photonics, actuation, sensing, and biotechnology. Here, recent advances in functional liquid crystals based on polymers, supramolecular complexes, gels, colloids, and inorganic-based hybrids are reviewed, from design strategies to functionalization of these materials and interfaces. New insights into liquid crystals provided by significant progress in advanced measurements and computational simulations, which enhance new design and functionalization of liquid-crystalline materials, are also discussed.

DNA-Modified Liquid Crystal Droplets

In this work, we have combined the advantages of sequence programmability of DNA nanotechnology and optical birefringence of liquid crystals (LCs). Herein, DNA amphiphiles were adsorbed onto LC droplets. A unique phenomenon of LC droplet aggregation was demonstrated, using DNA-modified LC droplets, through complementary DNA hybridization. Further functionalization of DNA-modified LC droplets with a desired DNA sequence was used to detect a wide range of chemicals and biomolecules, such as Hg²⁺, thrombin, and enzymes, through LC droplet aggregation and vice versa, which can be seen through the naked eye. These DNA-modified LC droplets can be printed onto a desired patterned surface with temperature-induced responsiveness and reversibility. Overall, our work is the first to report DNA-modified LC droplet, which provides a general detection platform based on the development of DNA aptamers. Additionally, this work inspires the exploration of surface information visualization combined with microcontact printing.

Simple and Rapid Detection of Ibuprofen─A Typical Pharmaceuticals and Personal Care Products─by a Liquid Crystal Aptasensor

This work established a liquid crystal (LC) aptasensor for simple and rapid detection of ibuprofen, a typical pharmaceuticals and personal care products (PPCPs) pollutant. A negatively charged DNA aptamer specific for ibuprofen and a positively charged amphiphilic surfactant, hexadecyltrimethylammonium bromide (CTAB), were incubated with the sample and then directly added onto the LC interface. In the presence of ibuprofen, the specific binding of ibuprofen with the DNA aptamer will release CTAB, which then adsorbed at the LC-aqueous interface and induced the orientational change of LCs to homeotropic orientation with a dark optical signal output. While in the absence of ibuprofen, the DNA aptamer binds with CTAB through hydrophobic and electrostatic interactions, LCs remained in the planar orientation with a bright optical signal output. This LC aptasensor also has good specificity for ibuprofen and can even detect ibuprofen drug in tap water. Moreover, the response time of the LC aptasensor is fast in minutes. Additionally, this LC aptasensor benefits in monitoring the water quality and inspires the exploration of a general platform for PPCPs detection.

Tailoring Liquid Crystals as Vehicles for Encapsulation and Enzyme-Triggered Release

Nanoscale assemblies of amphiphiles have been vividly explored in pharmaceutical formulations as drug nanocarriers. Aqueous interfaces of liquid crystals (LCs) are known to direct the self-assembly of a range of...

Development of Antibacterial Peptides with Efficient Antibacterial Activity, Low Toxicity, High Membrane Disruptive Activity and the Synergistic Antibacterial Effect

It is urgent to develop new antimicrobial drugs to overcome bacterial resistance which is a serious threat to human health. Antimicrobial peptides (AMPs) which are ideal substitutes for traditional antibiotics...

Combination of liquid crystal and deep learning reveals distinct signatures of Parkinson's disease-related wild-type α-synuclein and six pathogenic mutants

α-Synuclein is a central player in Parkinson's disease (PD) pathology. Various point mutations in α-synuclein have been identified to alter the protein-phospholipid binding behavior and cause PD. Therefore, exploration of α-synuclein-phospholipid interaction is important for understanding the PD pathogenesis and helping the early diagnosis of PD. Herein, a phospholipid-decorated liquid crystal (LC)-aqueous interface is constructed to investigate the binding between α-synucleins (wild-type and six familial mutant A30P, E46K, H50Q, G51D, A53E and A53T) and phospholipid. The application of deep learning analyzes and reveals distinct LC signatures generated by the binding of α-synuclein and phospholipid. This system allows for the identification of single point mutant α-synucleins with an average accuracy of 98.3±1.3% in a fast and efficient manner. We propose that this analytical methodology provides a new platform to understand α-synuclein-lipid interactions, and can be potentially developed for easy identification of α-synuclein mutations in common clinic.

Probing Nanoscale Lipid-Protein Interactions at the Interface of Liquid Crystal Droplets

Aqueous interfaces of liquid crystals (LCs) are widely explored in the design of functional interfaces to recapitulate the key aspects of biomolecular interactions in cellular milieu. Herein, using aqueous LC dispersions, we explore the interactions between mitochondrial cardiolipin and membrane-associated cytochrome c which play a pivotal role in the apoptotic signaling cascade. Conventional techniques used to decipher LC ordering at the droplet interface fail to give information about the interactions at a molecular level. Besides, owing to the complexity of LC systems and multiple determinants driving the LC reorientation, accurate analysis of the underlying mechanism responsible for the LC ordering transition remains challenging. Using a combination of atomistic simulations and microscopic and spectroscopic readouts, for the first time, we unveil the lipid-protein interactions that drive the reorientation at the LC droplet interface. The insights from our work are fundamental to the design of these interfaces for a spectrum of interfacial applications.

Applications of liquid crystals in biosensing

Liquid crystals (LCs), as a promising branch of highly-sensitive, quick-response, and low-cost materials, are widely applied to the detection of weak external stimuli and have attracted significant attention. Over the past decade, many research groups have been devoted to developing LC-based biosensors due to their self-assembly potential and functional diversity. In this paper, recent investigations on the design and application of LC-based biosensors are reviewed, based on the phenomenon that the orientation of LCs can be directly influenced by the interactions between biomolecules and LC molecules. The sensing principle of LC-based biosensors, as well as their signal detection by probing interfacial interactions, is described to convert, amplify, and quantify the information from targets into optical and electrical parameters. Furthermore, commonly-used LC biosensing targets are introduced, including glucose, proteins, enzymes, nucleic acids, cells, microorganisms, ions, and other micromolecules that are critical to human health. Due to their self-assembly potential, chemical diversity, and high sensitivity, it has been reported that tunable stimuli-responsive LC biosensors show bright perspectives and high superiorities in biological applications. Finally, challenges and future prospects are discussed for the fabrication and application of LC biosensors to both enhance their performance and to realize their promise in the biosensing industry.

Simple, rapid and sensitive detection of Parkinson's disease related alpha-synuclein using a DNA aptamer assisted liquid crystal biosensor

Alpha-synuclein (αS) has been proposed as a potential biomarker for the diagnosis of Parkinson's disease (PD). However, the detection of αS using a simple, rapid and sensitive approach is still challenging. Herein, we construct a new type of biosensor for the detection of αS, combining the stimuli-responsiveness of liquid crystals (LCs) and the specific interaction of a DNA aptamer with proteins. In principle, the positively charged surfactant hexadecyltrimethylammonium bromide (CTAB) binds with the negatively charged DNA aptamer via electrostatic interactions; in the presence of αS, the DNA aptamer specifically binds with αS and releases CTAB, which is an amphiphilic molecule and subsequently assembles at the LC-aqueous interface, resulting in a homeotropic alignment of LCs with a dark optical signal. In the absence of αS, CTAB binds with the DNA aptamer without affecting the alignment of LCs, which shows planar anchoring with a bright optical signal. The response time of LCs towards αS is rapid and can be down to minutes. The LC biosensor established here has a good specificity for αS and can recognize αS even from a mixture of proteins. The LC biosensor also exhibits high sensitivity with a limit of detection of αS as low as 10 pM, which is comparable to that of the enzyme-linked immunosorbent assay. This work provides a new strategy for the detection of αS in a simple, rapid and sensitive manner, possessing promising potentials towards early diagnosis and clinical applications.

A novel, label-free liquid crystal biosensor for Parkinson's disease related alpha-synuclein

A liquid crystal biosensor based on DNA aptamer for sensitive detection of Parkinson's Disease (PD) related alpha-synuclein was developed. This LC biosensor is constructed using a simple and label free method, and it not only enables early PD diagnosis, but also provides a general platform for detection based on DNA aptamer.

Biomolecular Binding at Aqueous Interfaces of Langmuir Monolayers of Bioconjugated Amphiphilic Mesogenic Molecules: A Molecular Dynamics Study

We report a molecular dynamics (MD) simulation study of protein binding at the aqueous-liquid crystal (LC) interfaces of bioconjugated mesogenic molecules. As a simple model of these interfaces, we use monolayers composed of biotin-conjugated or biotin-free amphiphilic mesogenic molecules and streptavidin in water. The all-atom MD simulations reveal that the binding of streptavidin to the biotin mesogenic monolayer is significantly stronger than that to biotin-free mesogenic monolayers. Although specific protein binding marginally increases the overall orientational order and the tilt of the biotin-conjugated mesogenic molecules of the monolayer, significant changes in tilt were observed near the bound protein (in contrast to the protein interaction with the monolayer without biotin). We also observe that specific protein binding changes the dynamic properties of the mesogens within the monolayer (e.g., lateral diffusion coefficients) and associated water. Overall, these MD simulations advance our understanding of the molecular-level phenomena involved in the binding of biomolecules and subsequent dynamic changes at the aqueous-LC interfaces. These results provide guidance to future molecular-level designs of biofunctional LC interfaces.