Self-assembly Technique Research Articles

Magnetoresponsive Artificial Cilia Self-Assembled with Magnetic Micro/Nanoparticles.

Biological cilia have exquisitely organized dynamic ultrafine structures with submicron diameters and exceptional aspect ratios, which are self-assembled with ciliary proteins. However, the construction of artificial cilia with size and dynamic functions comparable to biological cilia remains highly challenging. Here, we propose a self-assembly technique that generates magnetoresponsive artificial cilia with a highly ordered 3D structural arrangement using vapor-phase magnetic particles of varying sizes and shapes. We demonstrate that both monodispersed Fe3O4 nanoparticles and Fe microparticles can be assembled layer-by-layer vertically in patterned magnetic fields, generating both "nanoscale" or "microscale" artificial cilia, respectively. The resulting cilia display several structural features, such as diameters of single particle resolution, controllable diameters and lengths spanning from nanometers to micrometers, and accurate positioning. We further demonstrate that both the magnetic nanocilia and microcilia can dynamically and immediately actuate in response to modulated magnetic fields while providing different stroke ranges and actuation torques. Our strategy provides new possibilities for constructing artificial nano- and microcilia with controlled 3D morphology and dynamic field responsiveness using magnetic particles of varied sizes and shapes.

Biointerfacial giant capsules with high paclitaxel loading and magnetic targeting for breast tumor therapy

High drug loading, targeted delivery, prolonged drug release, and low systemic toxicity are effective weapons for hydrophobic drug delivery systems to solve serious concerns in poor water-solubility and toxicity of paclitaxel (PTX). Herein, we reported that biointerfacial giant multilayer microcapsules (BGMs) with the feature of high-density drug loading and high-efficiency magnetic delivery were fabricated templated by PTX-liposome-microbubble complex using the layer-by-layer self-assembly (LbL) technique. The drug loading capacity of BGMs was improved by optimizing the structure of microbubbles and capsules to increase the PTX-contained layers, and the resultant BGMs exhibited high drug loading content (50.56 ± 0.09 %) and sustained drug release properties. The BGMs with an average diameter of 74.1 ± 12.1 µm and an average thickness of 275.5 ± 48.4 nm contained abundant magnetic nanoparticles (MNPs) in their cavity, which endowed these capsules with outstanding magnetic properties and fast magnetophoretic velocity in the blood (∼0.3 mm/s, ▽B = 1 T/mm). Moreover, both in vitro and in vivo studies demonstrated that the biocompatible PTX-loaded magnetic BGMs (Capsule@PLMPPL) caused notable death (71.3 ± 2.9 %) of 4 T1 breast cancer cells through PTX diffusion, capsules degradation, and subsequent endocytosis by cancer cells, and ultimately effectively inhibited tumor growth. In general, the developed BGM with good deformability and degradation was the first reported giant polyelectrolyte capsule to be used in tumor therapy, which could notably improve the therapeutic efficacy of PTX while reducing its side effects.

High-Throughput and Efficient Intracellular Delivery Method via a Vibration-Assisted Nanoneedle/Microfluidic Composite System.

Intracellular delivery and genetic modification have brought a significant revolutionary to tumor immunotherapy, yet existing methods are still limited by low delivery efficiency, poor throughput, excessive cell damage, or unsuitability for suspension immune cells, specifically the natural killer cell, which is highly resistant to transfection. Here, we proposed a vibration-assisted nanoneedle/microfluidic composite system that uses large-area nanoneedles to rapidly puncture and detach the fast-moving suspension cells in the microchannel under vibration to achieve continuous high-throughput intracellular delivery. The nanoneedle arrays fabricated based on the large-area self-assembly technique and microchannels can maximize the delivery efficiency. Cas9 ribonucleoprotein complexes (Cas9/RNPs) can be delivered directly into cells due to the sufficient cellular membrane nanoperforation size; for difficult-to-transfect immune cells, the delivery efficiency can be up to 98%, while the cell viability remains at about 80%. Moreover, the throughput is demonstrated to maintain a mL/min level, which is significantly higher than that of conventional delivery techniques. Further, we prepared CD96 knockout NK-92 cells via this platform, and the gene-edited NK-92 cells possessed higher immunity by reversing exhaustion. The high-throughput, high-efficiency, and low-damage performance of our intracellular delivery strategy has great potential for cellular immunotherapy in clinical applications.

Turing patterns with high-resolution formed without chemical reaction in thin-film solution of organic semiconductors

Regular patterns can form spontaneously in chemical reaction-diffusion systems under non-equilibrium conditions as proposed by Alan Turing. Here, we found that regular patterns can be generated in uphill-diffusion solution systems without a chemical reaction process through both in-situ and ex-situ observations. Organic semiconductor solution is confined between two parallel plates with controlled micron/submicron-meter distance to minimize convection of the liquid and avoid spinodal precipitation at equilibrium. The solvent evaporation concentrates the solution gradually into an oversaturated non-equilibrium condition, under which a phase-transition occurs and ordered concentration-waves are generated. By proper tuning of the experimental parameter, multiple regular patterns with micro/nano-meter scaled features (line, square-grid, zig-zag, and fence-like patterns etc.) were observed. We explain the observed phenomenon as Turing-pattern generation resulted from uphill-diffusion and solution oversaturation. The generated patterns in the solutions can be condensed onto substrates to form structured micro/nanomaterials. We have fabricated organic semiconductor devices with such patterned materials to demonstrate the potential applications. Our observation may serve as a milestone in the progress towards a fundamental understanding of pattern formation in nature, like in biosystem, and pave a new avenue in developing self-assembling techniques of micro/nano structured materials.

On the computational modeling, additive manufacturing, and testing of tube-networks TPMS-based graphene lattices and characterizing their multifunctional properties

Lattices based on triply periodic minimal surfaces (TPMSs), which have been receiving increasing interest due to advances in additive manufacturing, are known now to be outperforming other cellular materials in several properties, enabling wider multifunctional applications. In this work, we focus on fabricating graphene TPMS lattices, viz., Gyroid, Schoen's I-WP (IWP), and Diamond, and investigate their multifunctional properties experimentally and computationally. The three-dimensional (3D) graphene structures were synthesized using a self-assembly hydrothermal-assisted dip-coating technique and the resulting lattices were tested for their mechanical, thermal, and electrical properties and compared to finite element simulation results. The graphene TPMS lattices resulting from the fabrication take the topology of a new class of TPMS architectures that are referred to here as the TPMS tube-networks. IWP demonstrated the highest elastic modulus as well as electrical and thermal conductivities. This study shows that 3D porous tube graphene can be utilized in designing new lightweight structural materials of low density with controllable thermal and electrical properties and mechanical strength with a potential to be employed in multifunctional engineering applications.

Fabrication and Characterization of Novel Silk Fiber-Optic SERS Sensor with Uniform Assembly of Gold Nanoparticles.

Biocompatible optical fibers and waveguides are gaining attention as promising platforms for implantable biophotonic devices. Recently, the distinct properties of silk fibroin were extensively explored because of its unique advantages, including flexibility, process compatibility, long-term biosafety, and controllable biodegradability for in vitro and in vivo biomedical applications. In this study, we developed a novel silk fiber for a sensitive optical sensor based on surface-enhanced Raman spectroscopy (SERS). In contrast to conventional plasmonic nanostructures, which employ expensive and time-consuming fabrication processes, gold nanoparticles were uniformly patterned on the top surface of the fiber employing a simple and cost-effective convective self-assembly technique. The fabricated silk fiber-optic SERS probe presented a good performance in terms of detection limit, sensitivity, and linearity. In particular, the uniform pattern of gold nanoparticles contributed to a highly linear sensing feature compared to the commercial multi-mode fiber sample with an irregular and aggregated distribution of gold nanoparticles. Through further optimization, silk-based fiber-optic probes can function as useful tools for highly sensitive, cost-effective, and easily tailored biophotonic platforms, thereby offering new capabilities for future implantable SERS devices.

Hypoglycemic Activity of Self-Assembled Gellan Gum-Soybean Isolate Composite Hydrogel-Embedded Active Substance-Saponin.

In order to avoid hemolysis caused by direct dietary of kidney tea saponin, complex gels based on gellan gum (GG) and soybean isolate protein (SPI) loaded with saponin were created in the present study by using a self-assembly technique. Studies were conducted on the rheological characteristics, encapsulation effectiveness, molecular structure, microstructure, and hypoglycemic activity of GG/SPI-saponin gels. Increasing the concentration of SPI helped to enhance the strength and energy storage modulus (G') of the gels, and the incorporation of high acylated saponin allowed the whole gel to undergo sol-gel interconversion. The encapsulation efficiency showed that GG/SPI-saponin was 84.52 ± 0.78% for saponin. Microstructural analysis results suggested that GG and SPI were bound by hydrogen bonds. The in vitro digestion results also indicated that saponin could be well retained in the stomach and subsequently released slowly in the intestine. In addition, the in vitro hypoglycemic activity results showed that the IC50 of encapsulated saponin against α-glucosidase and α-amylase were at 2.4790 mg/mL and 1.4317 mg/mL, respectively, and may be used to replace acarbose for hypoglycemia.

Polymerization-induced self-assembly of side-chain liquid crystalline copolymers by dissipative particle dynamics simulation

Side-chain liquid crystal copolymers can self-assemble into dispersed assemblies effectively with the polymerization-induced self-assembly (PISA) technique. However, the synergy of polymerization and self-assembly result in undefined self-assembly behavior and polymerization kinetics. We explored the PISA behavior of side-chain liquid crystal copolymers in selective solvents by combining dissipative particle dynamics simulation and a probability-based reaction model. It was found that the morphologies of assemblies depend on the PISA time, copolymer concentrations, and various structural parameters. The polymerization exhibits three stages with different reaction constants during the PISA, achieving low polydispersity of the produced copolymers. The comparison with experiments demonstrated that the simulation could capture the essential characteristics of PISA. This study can help fundamentally understand the PISA behavior of side-chain liquid crystal copolymers.

A strategy to promote the ORR electrocatalytic activity by the novel engineering bunched three-dimensional Pd-Cu alloy aerogel

Pd has been considered as a potential substitution of the Pt-based electrocatalyst for oxygen reduction reaction (ORR) in the fields of fuel cells, however, the binding strength between the bare surface and the intermediates is much stronger than that on Pt, leading to its inferior ORR activity. Alloying noble metals with nonprecious metals provides a cost-effective strategy for electrocatalyst design. In this work, we have demonstrated a novel Pd3Cu aerogel electrocatalyst derived from a mild reduction agent via the self-assembly and freeze-drying technique. The resulting catalyst shows a typical three-dimensional and “pearl-like” aerogel structure. Combining the structural features and optimized chemical compositions, the Pd3Cu aerogel exhibits remarkable pH-independent performance over the commercial Pt/C electrocatalyst. Notably, the optimized Pd3Cu aerogel displays excellent ORR activity with a half-wave potential of 0.90 V vs RHE, with a limiting current density of 5.8 mA/cm2 under the alkaline conditions, which is among the best of the reported noble metal-based ORR electrocatalysts. In addition, the resulting Pd3Cu aerogel delivers excellent hydrogen evolution reaction (HER) and ethanol oxidation reaction (EOR) performance. Furthermore, the density functional theory (DFT) calculations reveal that the unique partially oxidized Pd3Cu aerogel has led to a shift‐down of the d-band center of the active sites, which energetically optimizes the binding strength of the adsorbed O intermediate during the ORR process, therefore accelerating the ORR activity. These findings provide a new pathway for the integrated engineering of geometric and electronic structures of metal alloys to improve their electrocatalytic property.

Rationally designed rGO@CNTs@CNFs film as self-supporting binder-free Si electrodes for high-performance lithium-ion batteries

Si has become the most promising anode materials for lithium-ion batteries (LIBs) due to its high theoretical specific capacity and comparable low discharge potential. However, the practical usage of Si is still hindered by its huge volume expansion. To release volume stress and improve conductance, designed self-supporting binder-free Si electrode endowed with three-dimensional structure has been come up in this research. The pore structure is adjusted by rationally designing the proportion of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) to alleviate volume change. Simultaneously, construct stable conductivity network was fabricated via ice crystal self-assemble freezing technique following compress and carbonization process. The electrochemical specific capacity of rGO@CNTs@CNFs@Si-2 electrode has stably remained at 2250 mAh/g after 100 cycles (100 mA/g) with benign rate capabilities. This simple self-assemble method for self-supporting binder-free Si electrode would open a new route to exploit high energy density Si-based electrode for flexible LIBs.

Researching proton conduction behavior at subzero temperature of lamellar anhydrous proton exchange membranes

For proton exchange membranes (PEMs), many studies have been going into the anhydrous PEMs with the working temperature exceeding 110 °C and the humidified PEMs below 80 °C. However, the PEMs fracture can cause cold start failure while the fuel cell vehicles are exposed to a colder climate for a long-time parking. In this study, low temperature PEMs (LTPEMs) with the lamellar structure was constructed through the well-ordered dispersion of Kevlar nanofibers, thioglycollic acid capping cadmium telluride (CdTe) nanocrystals and polyurethane (PU) polymer, expecting to enhance the mechanical property and improve the proton conductivity at subzero temperature. The successful preparation of the LTPEMs with spin coating technique and layer by layer self-assembly technique was determined by the structure analysis and the property measurement. The compact microstructure was constructed owing to electrostatic attraction and intermolecular hydrogen bonding. In the prepared (Kevlar/CdTe)25/(PU/CdTe)100 membrane, Kevlar nanofibers provided the support and PU molecular chains guaranteed enough flexibility. Furthermore, a massive amount of CdTe nanocrystals could tolerate low temperature condition, which was derived from the high proton conductivity at subzero temperature. Specifically, the (Kevlar/CdTe)25/(PU/CdTe)100/PA membrane exhibited the proton conductivity values of (2.23 ± 0.39) × 10−2 S/cm at −30 °C, (6.59 ± 0.15) × 10−2 S/cm at 0 °C and (1.73 ± 0.04) × 10−1 S/cm at 30 °C. Most importantly, the fine proton conductivity stability was revealed from the proton conductivity values of 3.72 × 10−2 S/cm at −30 °C after a thirty-cycle heating/cooling process and 3.53 × 10−2 S/cm at −30 °C after a 1020 h non-stop test. Furthermore, there was a slight decrease on the tensile stress with PA molecules doping owing to the compact microstructure.

Eggshell-Graphene Oxide Layer as Membrane Filtration for Removal Methylene Blue in Waste Water

Eggshell (ES) membrane is a semipermeable membrane that is insoluble in water and has a high surface area. We modified ES membranes with graphene oxide (GO) using self-assembled technique and used it to remove dye pollutants such as methylene blue (MB) in water. The ES membranes were obtained from fresh eggs that have been removed from albumen and yolk, then immersed in 15% acetic acid for 30 minutes. The ES membranes were immersed in 0.5 mg/mL dispersed GO and ultrasonicated for 3 hours. The modified ES-GO membrane was then used to filter 5 mg/L MB solutions. Filtration of MB solution was performed by pouring the solution over the ES-GO membrane with a help of constant pressure of 45 psi. We found that the modified ES-GO membrane could filter MB up to 33.53% and reduce MB concentration from 4.91 mg/L to 3.53 mg/L. The result of membrane permeability is 2.488 x10−3 darcy and the flow rate of the filtration is relatively constant about 4 mL/s.

Superb photocatalytic activity of 2D/2D Cl doped g-C3N4 nanodisc/Bi2WO6 nanosheet heterojunction: Exploration of photoinduced carrier migration in S-scheme heterojunction

The intimately-contact 2D/2D heterojunction structure could provide optimal charge transfer/separation interfaces to effectively separate photoinduced charge carriers, thus improving photocatalytic performance. An electrostatic self-assembly technique was applied to construct the 2D/2D Cl doped g-C3N4 nanodisc/regular rectangular Bi2WO6 nanosheet heterojunction (ClCN/Bi2WO6) in this work. The physicochemical properties of as-prepared samples were systematically characterized by Zeta potential, XRD, FT-IR, SEM, TEM, HR-TEM, XPS, BET, UV–vis DRS, PL, EIS, photocurrent and Mott-Schottky. The maximum photocatalytic hydrogen (H2) generation (421.44 mol g−1 h−1) and photodegradation methyl orange (MO) performance (99%, 40 min) under simulated sunlight irradiation were demonstrated by the 10% ClCN/Bi2WO6, which was 14.1 times and 4.9 times more effective than Bi2WO6. Moreover, the apparent quantum efficiency (AQE) of 10% ClCN/Bi2WO6 is 9.6% at 420 nm. Based on calculations using DFT (density functional theory), the mechanism and driving force of charge transfer and separation of S-scheme heterojunction in this work were investigated and addressed in detail. This study advances the potential evolution of the S-scheme mechanism by offering a unique procedure for the fabrication of 2D/2D heterojunction photocatalysts.

Advances in preparation and application of carbon nanotube films

Nanotechnology is recognized as one of the high and new technologies in the 21st century. Carbon nanotubes have been widely used in molecular sieve, drug transport and seawater desalination due to their unique mechanical, electrical, optical and other excellent properties. As the main representative of carbon nanotube macroscopic materials, carbon nanotube film not only retains the microscopic properties of carbon nanotube, but also has good mechanical properties and stable chemical properties. The preparation and application of carbon nanotubes (CNTS) have attracted extensive attention from scholars at home and abroad. In this paper, the research on carbon nanotube films in recent years is reviewed. Based on the preparation of carbon nanotube films, chemical vapor deposition, LB (Langmuir-Blodgett) film and electrostatic layer-by-layer self-assembly techniques are briefly described. In addition, the applications of carbon nanotubes in biological field, photoelectric nano devices, water treatment, seawater desalination and other fields are also described.

Surface Presentation of Hyaluronic Acid Modulates Nanoparticle-Cell Association.

Nanoparticle (NP) drug carriers have revolutionized medicine and increased patient quality of life. Clinically approved formulations typically succeed because of reduced off-target toxicity of the cargo. However, increasing carrier accumulation at disease sites through precise targeting remains one of the biggest challenges in the field. Novel multivalent ligand presentations and self-assembled constructs can enhance cell association, but an inability to draw direct comparisons across formulations has hindered progress. Furthermore, how nanoparticle structure influences function often is unclear. In this report, we leverage the well-characterized hyaluronic acid (HA)-CD44 binding pair to investigate how the surface architecture of modified NPs impacts their association with ovarian cancer cells that overexpress CD44. We functionalized anionic liposomes with 5 kDa HA by either covalent conjugation via surface coupling or electrostatic self-assembly using the layer-by-layer (LbL) adsorption method. Comparing these two methods, we observed a consistent enhancement of NP-cell association with the self-assembly LbL technique, particularly with higher molecular weight (≥10 kDa) HA. To further optimize association, we increased the surface-available HA. We synthesized a bottlebrush glycopolymer composed of a polynorbornene backbone and pendant 5 kDa HA and layered this macromolecule onto NPs. Flow cytometry revealed that the LbL HA bottlebrush NP outperformed the LbL linear display of HA. Cellular visualization by deconvolution optical microscopy corroborated results from all three constructs. Using exogenous HA to block NP-CD44 interactions, we found the LbL HA bottlebrush NP had a 4-fold higher binding avidity than the best-performing LbL linear HA NP. We further observed that decreasing the density of HA bottlebrush side chains to 75% had minimal impact on LbL NP stability or cell association, though we did see a reduction in binding avidity with this side-chain-modified NP. Our studies indicate that LbL surfaces are highly effective for multivalent displays, and the mode in which they present a targeting ligand can be optimized for NP cell targeting.

High-efficiency charge separation of Z-scheme 2D/2D C3N4/C3N5 nonmetal VdW heterojunction photocatalyst with enhanced hydrogen evolution activity and stability

The interfacial charge transfer control is a key and arduous issue for propelling the migration/separation of photogenerated carriers for heterojunction photocatalysts. Here, a new 2D/2D C3N4/C3N5 nonmetal van der Waals (VdW) heterojunction is fabricated by the simple self-assembly technique in acidic medium, whose charge separation efficiency is promoted dramatically, thus being endowed with the high-efficiency photocatalytic hydrogen evolution (PHE) performance. The PHE rate reaches up to 3.33 mmol h−1 g−1 under the visible light and the apparent quantum efficiency (AQE) of 20.6% is achieved at 420 nm on the optimal 2D/2D C3N4/C3N5-5% sample. Furthermore, the 2D/2D C3N4/C3N5 nonmetal VdW heterojunction also exhibits the desired stability because there was no significant decrease after PHE reaction of 10 cycles with total 40 h. Such outstanding PHE activity and stability originate from the impelled separation of photoinduced charge carriers and the powerful interfacial interaction through forming Z-Scheme charge transfer path and π-π coupling effect between C3N4 and C3N5 nanosheets. This work takes a significant guiding and demonstration for designing and exploiting other novel nonmetallic polymer-based VdW heterojunctions in the photocatalytic application field.

Iron ions induced self-assembly of graphene oxide lubricating coating with self-adapting low friction characteristics

Graphene oxide (GO) is a promising solid lubricant for moving mechanical systems to implement reliable and effective lubrication due to its easy modification and excellent tribological properties. However, obtaining highly dense GO coatings simultaneously with high hardness and extensibility is still a challenge for available self-assembly techniques, and these characteristics are beneficial to tribological properties. Inspired by the advanced abrasion resistance system of mussel byssus threads, a surprisingly simple and versatile metal ions (namely Fe2+ and Fe3+ ions) directed self-assembly strategy has been developed to rapidly fabricate GO coatings. GO as a solid lubricant is highly sensitive to the interface structure and test environment. Consequently, the influence of the valence state of iron ions on the macroscopic tribological properties of GO-based coatings in air, nitrogen gas and vacuum environments are comparatively investigated. The results show that the GO-Fe3+ coating with a highly compact characteristic and unique granular microarchitecture resulting in higher hardness and strain capacity displays a lower friction coefficient and remarkable wear resistance than the GO-Fe2+ coating. Additionally, because water molecules generate strong hydrogen bonding gradually disrupting the ordered layered structure, both GO-Fe2+ and GO-Fe3+ coatings exhibit a higher friction coefficient in air than in nitrogen gas and vacuum.

One-step fabrication of lidocaine/CalliSpheres® composites for painless transcatheter arterial embolization

BackgroundTranscatheter arterial embolization (TAE) is one of the first-line treatments for advanced hepatocellular cancer. The pain caused by TAE is a stark complication, which remains to be prevented by biomedical engineering methods.MethodsHerein, a commercial embolic agent CalliSpheres® bead (CB) was functionally modified with lidocaine (Lid) using an electrostatic self-assembly technique. The products were coded as CB/Lid-n (n = 0, 5, 10, corresponding to the relative content of Lid). The chemical compositions, morphology, drug-loading, and drug-releasing ability of CB/Lid-n were comprehensively investigated. The biocompatibility was determined by hemolysis assay, live/dead cell staining assay, CCK8 assay, immunofluorescence (IHC) staining assay and quantitative real-time PCR. The thermal withdrawal latency (TWL) and edema ratio (ER) were performed to evaluate the analgesia of CB/Lid-n using a plantar inflammation model. A series of histological staining, including immunohistochemistry (IL-6, IL-10, TGF-β and Navi1.7) and TUNEL were conducted to reveal the underlying mechanism of anti-tumor effect of CB/Lid-n on a VX2-tumor bearing model.ResultsLid was successfully loaded onto the surface of CalliSpheres® bead, and the average diameter of CalliSpheres® bead increased along with the dosage of Lid. CB/Lid-n exhibited desirable drug-loading ratio, drug-embedding ratio, and sustained drug-release capability. CB/Lid-n had mild toxicity towards L929 cells, while triggered no obvious hemolysis. Furthermore, CB/Lid-n could improve the carrageenan-induced inflammation response micro-environment in vivo and in vitro. We found that CB/Lid-10 could selectively kill tumor by blocking blood supply, inhibiting cell proliferation, and promoting cell apoptosis. CB/Lid-10 could also release Lid to relieve post-operative pain, mainly by remodeling the harsh inflammation micro-environment (IME).ConclusionsIn summary, CB/Lid-10 has relatively good biocompatibility and bioactivity, and it can serve as a promising candidate for painless transcatheter arterial embolization.

Urease-modified LAPS: Two-dimensional dynamic detection of enzymatic reactions

• Urea-sensitive LAPS fabricated by a layer-by-layer self-assembly technique. • The enzymatic reactions are monitored dynamically in spatially resolved manner. • A method for the selection of monitoring windows based on threshold intersections. • The 2D images are more uniform and reduce demand for the number of pixel points. Light addressable potentiometric sensor (LAPS) is a semiconductor-based electrochemical sensor with flat surface structure and superior light addressability, making it an ideal platform for visualizing enzymatic reactions. However, it is hardly to observe the true process of reactions because a large amount of information unrelated to the enzymatic reaction, such as buffer diffusion caused by pH gradient, is contained in photocurrent images. In this study, urea-sensitive LAPS were obtained by immobilizing urease on the surface of LAPS with Si/SiO 2 /Si 3 N 4 structured using a layer-by-layer self-assembly technique and a method for the selection of enzymatic reaction monitoring windows based on threshold intersections is proposed to reduce the influence of non-enzymatic reaction factors. The overall performance of the urea-sensitive LAPS was excellent, with a sensitivity of 92.04 ± 4.04 mV/pC urea and a linearity of 99.16 % in the range of 1–20 mM. The mean square error of photocurrent images using this method is reduced by an order of magnitude compared to original images, which are more uniform and reduce the pixel demand. Our work provides a more complete assessment of urea-sensitive LAPS, and the proposed window selection method based on threshold intersections provides a viable method for dynamic monitoring of chemical images with high uniformity and high refresh rates.

Construction of CS/BSA multilayers for electrochemical recognition of tryptophan enantiomers

• A chiral interface based on chitosan (CS) and bovine serum albumin (BSA) was fabricated by simple self-assembly technique. • The chiral recognition of Trp enantiomers at (CS/BSA) 1.5 /GCE was demonstrated by DPV and contact angle measurements. • The percentage of L-Trp or D-Trp in a non-racemic mixture solution can be accurately predicted by (CS/BSA) 1.5 /GCE chiral interface. Ultra stable and reproducible electrochemical chiral interface ((CS/BSA) 1.5 /GCE) based on chitosan (CS) and bovine serum albumin (BSA) was fabricated using layer-by-layer (LbL) self-assembly technique. Its structure and properties were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and electrochemical methods. Snowflake like morphology was observed on the (CS/BSA) 1.5 films using SEM. Interestingly, the (CS/BSA) 1.5 chiral interface achieved chiral recognition of D-Trp and L-Trp via contact angle measurements. Under optimized experimental conditions, differential pulse voltammetry (DPV) results showed that the peak current ratio of D-Trp to L-Trp (I D /I L ) was 3.83 at (CS/BSA) 1.5 /GCE (glass carbon electrode). In addition, there was a good linear relationship between the peak current and Trp enantiomer concentration in the range of 0.005–0.15 mM. Our study shows the (CS/BSA) 1.5 /GCE can be used to quickly determine the ratio of enantiomers in non-racemic Trp mixture solutions, which is of great significance for the chiral recognition in non-racemic mixtures of chiral compounds.