LbL Assembly Research Articles

Electrostatic adsorption of polyanions onto lipid nanoparticles controls uptake, trafficking, and transfection of RNA and DNA therapies

Rapid advances in nucleic acid therapies highlight the immense therapeutic potential of genetic therapeutics. Lipid nanoparticles (LNPs) are highly potent nonviral transfection agents that can encapsulate and deliver various nucleic acid therapeutics, including but not limited to messenger RNA (mRNA), silencing RNA (siRNA), and plasmid DNA (pDNA). However, a major challenge of targeted LNP-mediated systemic delivery is the nanoparticles' nonspecific uptake by the liver and the mononuclear phagocytic system, due partly to the adsorption of endogenous serum proteins onto LNP surfaces. Tunable LNP surface chemistries may enable efficacious delivery across a range of organs and cell types. Here, we describe a method to electrostatically adsorb bioactive polyelectrolytes onto LNPs to create layered LNPs (LLNPs). LNP cores varying in nucleic acid cargo and component lipids were stably layered with four biologically relevant polyanions: hyaluronate (HA), poly-L-aspartate (PLD), poly-L-glutamate (PLE), and polyacrylate (PAA). We further investigated the impact of the four surface polyanions on the transfection and uptake of mRNA- and pDNA-loaded LNPs in cell cultures. PLD- and PLE-LLNPs increased mRNA transfection twofold over unlayered LNPs in immune cells. HA-LLNPs increased pDNA transfection rates by more than twofold in epithelial and immune cells. In a healthy C57BL/6 murine model, PLE- and HA-LLNPs increased transfection by 1.8-fold to 2.5-fold over unlayered LNPs in the liver and spleen. These results suggest that LbL assembly is a generalizable, highly tunable platform to modify the targeting specificity, stability, and transfection efficacy of LNPs, as well as incorporate other charged targeting and therapeutic molecules into these systems.

Deposition of multilayer coatings onto highly porous materials by Layer-by-Layer assembly for bone tissue engineering applications using cyclic mechanical deformation and perfusion

Manufacturing LbL assembly coated highly 3D-porous scaffolds under dynamic conditions using continuous perfusion and cyclic compression significantly enhances their physicomechanical properties compared to those fabricated under static conditions.

LBL assembled graphene oxide-based nanofiltration membranes with tunable surface charges and high selectivity for charged organic dye molecules

In this work, 2D ultrathin positively-charged α-nickel hydroxide (α-Ni(OH)2) nanosheets composite with negatively-charged graphene oxide (GO) to prepare composite membrane by LBL assembly technology. The strong electrostatic interaction between α-Ni(OH)2 and GO improved the structural stability of the interlayer channels of GO/α-Ni(OH)2 composite membranes. Moreover, the surface charge and thickness of the membrane can be easily regulated by assembly layer numbers. Compared with the unmodified GO membrane, the GO/α-Ni(OH)2 membrane with nanometer thickness inhibited the membrane swelling and achieved controlled sieving of charged molecules.

A Novel Hydrophilic, Antibacterial Chitosan-Based Coating Prepared by Ultrasonic Atomization Assisted LbL Assembly Technique.

To explore the potential applicability of chitosan (CTS), we prepared aldehyde chitosan (CTS-CHO) with chitosan and sodium periodate via oxidation reaction and then a chitosan-based hydrophilic and antibacterial coating on the surface of poly (lactic acid) (PLA) film was developed and characterized. The oxidation degree was determined by Elemental analyser to be 12.53%, and a Fourier transform infrared spectroscopy was used to characterize the structure of CTS-CHO. It was evident that CTS-CHO is a biocompatible coating biomaterial with more than 80% cell viability obtained through the Live/Dead staining assay and the alamarBlue assay. The hydrophilic and antibacterial CTS-CHO coating on the PLA surface was prepared by ultrasonic atomization assisted LbL assembly technique due to Schiff's base reaction within and between layers. The CTS-CHO coating had better hydrophilicity and transparency, a more definite industrialization potential, and higher antibacterial activity at experimental concentrations than the CTS coating. All of the results demonstrated that the ultrasonic atomization-assisted LbL assembly CTS-CHO coating is a promising alternative for improving hydrophilicity and antibacterial activity on the PLA surface. The functional groups of CTS-CHO could react with active components with amino groups via dynamic Schiff's base reaction and provide the opportunity to create a drug releasing surface for biomedical applications.

Fabrication of an Eco-Friendly Clay-Based Coating for Enhancing Flame Retardant and Mechanical Properties of Cotton Fabrics via LbL Assembly.

An eco-friendly clay-based synergistic flame-retardant coating was established on cotton fabrics via facile layer-by-layer assembly derived from polyethyleneimine (PEI), attapulgite clay (ATP), and phytic acid (PA). The fabricated flame-retardant (FR) cotton fabrics demonstrated improved thermal stability. Compared to untreated cotton fabrics, the limiting oxygen index of Cotton-8TL was improved to 27.0%. The peak heat release rates of the prepared FR cotton fabrics were lower than that of the pristine cotton fabrics, showing a maximum reduction of 41%. The deposition coating system improved the amount of char residue effectively. The intumescent flame-retardant mechanism was proposed through the analysis of char residue and the suppression properties of volatile gases. Furthermore, compared with those of the untreated cotton fabrics, the tensile strength and elongation at break of the FR cotton fabrics in the warp direction were improved by 20% and 47% remarkably, respectively. A feasible surface modification strategy was provided for the flame-retardant treatment of cotton fabrics with the improvement of mechanical properties.

Synergistic combination therapy delivered via layer-by-layer nanoparticles induces solid tumor regression of ovarian cancer.

The majority of patients with high grade serous ovarian cancer (HGSOC) develop recurrent disease and chemotherapy resistance. To identify drug combinations that would be effective in treatment of chemotherapy resistant disease, we examined the efficacy of drug combinations that target the three antiapoptotic proteins most commonly expressed in HGSOC-BCL2, BCL-XL, and MCL1. Co-inhibition of BCL2 and BCL-XL (ABT-263) with inhibition of MCL1 (S63845) induces potent synergistic cytotoxicity in multiple HGSOC models. Since this drug combination is predicted to be toxic to patients due to the known clinical morbidities of each drug, we developed layer-by-layer nanoparticles (LbL NPs) that co-encapsulate these inhibitors in order to target HGSOC tumor cells and reduce systemic toxicities. We show that the LbL NPs can be designed to have high association with specific ovarian tumor cell types targeted in these studies, thus enabling a more selective uptake when delivered via intraperitoneal injection. Treatment with these LbL NPs displayed better potency than free drugs in vitro and resulted in near-complete elimination of solid tumor metastases of ovarian cancer xenografts. Thus, these results support the exploration of LbL NPs as a strategy to deliver potent drug combinations to recurrent HGSOC. While these findings are described for co-encapsulation of a BCL2/XL and a MCL1 inhibitor, the modular nature of LbL assembly provides flexibility in the range of therapies that can be incorporated, making LbL NPs an adaptable vehicle for delivery of additional combinations of pathway inhibitors and other oncology drugs.

Glucose-activatable insulin delivery with charge-conversional polyelectrolyte multilayers for diabetes care.

One of the most effective treatments for diabetes is to design a glucose-regulated insulin (INS) delivery system that could adjust the INS release time and rate to reduce diabetes-related complications. Here, mixed multiple layer-by-layer (mmLbL)-INS microspheres were developed for glucose-mediated INS release and an enhanced hypoglycemic effect for diabetes care. To achieve ultrafast glucose-activated INS release, glucose oxidase (GOx) was assembled with a positively charged polymer and modified on INS LbL. The mmLbL-INS microspheres were constructed with one, two, and four layers of the polyelectrolyte LbL assembly at a ratio of 1:1:1. Under hyperglycemia, GOx converts a change in the hyperglycemic environment to a pH stimulus, thus providing sufficient hydrogen ion. The accumulated hydrogen ion starts LbL charge shifting, and anionic polymers are converted to cationic polymers through hydrolytic cleavage of amine-functionalized side chains. The results of in vitro INS release suggested that glucose can modulate the mmLbL-INS microspheres in a pulsatile profile. In vivo studies validated that this formulation enhanced the hypoglycemic effect in STZ-induced diabetic rats within 2 h of subcutaneous administration and facilitated stabilization of blood glucose levels for up to 2 days. This glucose-activatable LbL microsphere system could serve as a powerful tool for constructing a precisely controlled release system.

Fabrication of transparent ultrathin films with ordered solid luminescence by LBL assembly of CdTe quantum dots with exfoliated vermiculite

Quantum dots luminescent films have great potential for application in lasers, optoelectronics, solid-state light-emitting diodes, and optical devices. This work describes multilayer ordered vermiculite-based luminescent thin films (VLFs) with 2D architecture via layer-by-layer assembly of PDDA-modified CdTe QDs on exfoliated vermiculite (VMT). The assembly of negative CdTe QDs and negative VMT was achieved, overcoming the nonluminance of solid CdTe QDs. The ordered VLFs possess periodic layered structures involving heterogeneous superlattices associated with individual VMT layers. The rational combination of luminescent components affords precise control of the emission wavelength and intensity, resulting in a gradual change in luminescence intensity in the selected light-emitting spectral region upon increasing the number of deposition cycles. Compared to the CdTe QDs, the fluorescence lifetime of VLFs is improved owing to the ordered structure. This work provides a facile approach to fabricate heterogeneous VLFs with high luminous properties and optical stability, which is expected to prevent easy aggregation of luminescent materials and can be potentially applied in light displays and multicolor optical and optoelectronic devices.

Layered Biomimetic Composites from MXenes with Sequential Bridging

AbstractLayer‐by‐layer (LbL) assembly is a widely used technique for the self‐assembly of layered nanocomposites from clay sheets, carbon nanotubes, graphene oxide, nanoparticles, and other materials. Other approaches for fabricating layered nanocomposites include vacuum‐assisted filtration and blade coating. They are simpler than LbL assembly, but they all introduce voids into the layered structure, thereby reducing the performance of the resulting nanocomposites. A team from Beihang University evaluated the void structure in Ti3C2Tx MXene composites and found that the fundamental problem with voids can be solved by the sequential nanoscale bonding of MXEne platelets with sodium carboxymethyl cellulose combined with covalent bridging with borate ions, thereby opening a new path to self‐assemble two‐dimensional platelets into continuous high‐performance layered nanocomposites.

DNA-mediated assembly of a gold-nanoparticle film with controllable sonic behavior detected by novel electric-induced ultrasound.

Two-dimensional gold-assembled nanomaterials have garnered considerable interest in biomedical applications such as wearable sensors and flexible devices. The assembly can be accomplished via attractive interactions between gold nanoparticles (GNPs) and a standard polymer. It is highly desirable and a great challenge to develop a new assembly method that can provide formed materials with novel properties. In this work, we explored complementary DNA-functionalized gold nanoparticles (DNA-GNPs) as building blocks to establish multifunctional two-dimensional gold nanomaterials via layer-by-layer (LBL) assembly. We found that the DNA-mediated assembly endows GNP films with a superlattice and their sonic behavior could be regulated in a controllable manner through altering the sequence of SH-DNA and linker DNA, which was detected by the electric-induced ultrasound method. Our observation suggested that this DNA-mediated assembly of GNP films with controllable sonic behaviors could greatly promote the biomedical application of two-dimensional assembled-gold nanomaterials.

Layer-by-layer assembly methods and their biomedical applications.

Layer-by-layer (LbL) assembly has attracted much interest because of its ability to provide nanoscale control over film characteristics and because of a wide choice of available materials. The methods of LbL not only determine the process properties, but also directly affect film properties. In this review, we will discuss LbL methodologies that have been used in biomedical fields. Special attention is devoted to different properties arising from methods that allow for diverse biomedical applications, ranging from surface modification to tissue engineering. We conclude with a discussion of the current challenges and future perspectives.

Characteristics of Cesium Adsorption by Alginate Bead Adsorbent with Layer-by-Layer Synthesis of Prussian Blue

Objectives : The purpose of this study was to develop an adsorbent to which Prussian blue (PB) is stably immobilized to remove radioactive cesium (Cs).Methods : Prussian blue-Alginate (PA) bead and Prussian blue-Alginate with Layer-by-layer synthesis (PAL) bead were synthesized by immobilizing PB respectively.Results and Discussion : As a results of XRD and FT-IR analysis, PB was successfuuly immobilized in alginate bead and PA, PAL bead. SEM (EDS) and TG analysis data were confirmed that the PB content of the PAL bead to which the LBL synthesis method was applied was improved by 6.31%. It was confirmed that the Cs adsorption capacity was improved through the LBL assembly process. The maximum adsorption amount (qm) of PA bead was 25.783 mg/g, and PAL bead was mg/g. In addition, as a result of UV-vis analysis of washing water after synthesis of PA bead and PAL bead, it was confirmed that the PB desorption of the PAL bead was lower indicating that the stability was also improved by LBL synthesis.Conclusions : We developed an adsorbent which prussianblue immobilized on alginate bead for selective removal cesium in aqueous solution. PB was immobilized by LBL synthesis method qm of PAL beads was 28.294 mg/g. It was expected to applied effectively and stably to radioactive cesium contaminated water.

Gentamicin loaded polyelectrolyte multilayers and strontium doped hydroxyapatite composite coating on Ti-6Al-4V alloy: antibacterial ability and biocompatibility

ABSTRACT In order to realise the biocompatibility and antibacterial activity of Ti alloy to meet the requirements of oral and orthopaedic applications, drug-loaded hydroxyapatite coatings doped with strontium were designed and constructed on the surface of Ti alloy using layer-by-layer assembly and hydrothermal treatment. The obtained coating was characterised by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. The biological assays showed that the composite coating exhibited excellent biocompatibility and antibacterial activity. Therefore, based on the in vitro studies, it can be claimed that the LbL assembly and the multifunctional coating can act as a promising surface-engineering strategy for the functionalization of Ti alloy in clinical trials.

Composite Materials by Building Block Chemistry Using Weak Interaction

Abstract Layer-by-Layer (LbL) assembly of interactive polymers onto surfaces leads to the construction of multilayered ultrathin films, which can be done simply by alternately dipping the substrate into various solutions. The range of applications of this LbL assembly can be broadened by introducing molecular recognition mechanisms for polymers and proteins, and by using weak interactions such as van der Waals interactions and biological recognition. As a specific example, it can be applied to the formation of stereocomplexes of poly(methyl methacrylate) (PMMA), poly-lactide (PLA), and fibronectin-collagen as extracellular matrix proteins. In weakly interacting LbL assemblies, the polymer chain tends to be placed in the most structurally stable state. This feature has been successfully used for template polymerization of stereoregular polymers, significant morphological control of biodegradable nanomaterials, and fabrication of three-dimensional (3D) cellular tissue constructs. LbL assembly based on weak interactions is expected to further stimulate interest in the interdisciplinary fields of bioscience and polymer chemistry. Using LbL technology to create functional 3D tissues, such as skin models (LbL-3D Skin) and heart models (LbL-3D Heart), will be a breakthrough in science and technology.

The thermal degradation property and flame-retardant mechanism of coated knitted cotton fabric with chitosan and APP by LBL assembly

In order to improve the flame retardancy of knitted cotton fabrics and investigate the flame-retardant mechanism of the system formed by ammonium polyphosphate (APP) and chitosan (CS), flame-retardant knitted cotton fabrics coated with APP and CS were successfully prepared by layer by layer assembly. APP and CS formed the intumescent flame-retardant system, in which CS acted as the carbon source agent and APP acted as both the acid source and foaming agent. The surface micromorphologies before and after flaming of coated knitted cotton fabrics were exploited by scanning electron microscopy. The flammability, combustion behaviors, thermal degradation properties and flame-retardant mechanism of this system were investigated by vertical burning test, cone calorimetry test and thermogravimetric analysis coupled with Fourier transform infrared analysis in N2 atmosphere, respectively. Compared with the control sample, the deposition of APP and CS endowed the knitted cotton fabrics with improved flame retardancy, higher residual chars, lower heat release rate and total heat release, while increased the smoke production. Improved flame-retardant behaviors are attributed to the thermally stable residual chars, more release of inflammable gases and potential free radical scavengers (PO·) in the gaseous products, named the combination of the condensed-phase and gaseous-phase flame-retardant mechanism.

Bio-inspired nanocomposite by layer-by-layer coating of chitosan/hyaluronic acid multilayers on a hard nanocellulose-hydroxyapatite matrix

This study proposed a layer-by-layer technique on the hard CNCs/hydroxyapatite (HAP) matrix using biodegradable and biocompatible chitosan and hyaluronic acid (HA). Inspired by the mineralized collagen in human bone, the CNCs/HAP matrix was synthesized by a facile in situ HAP coating on the CNCs fibers. The chemical and crystalline structure of the CNCs/HAP matrix was investigated with FTIR, XRD, HRTEM, and SAED. The surface of the CNCs/HAP matrix was analyzed by AFM which showed a flat structure with a roughness of 23.12 nm, however, the surface roughness increased to 56.09 nm with the assembly of chitosan and HA. After the LBL assembly, the surface hydrophilicity of the CNCs/HAP films was improved. Moreover, the CNCs/HAP matrix showed enhanced mechanical property than pure CNCs matrix. Although there is compromise in the mechanical property after the LBL assembly, it is anticipated its bioaffinity and biocompatibility will increase with the incoporation of chitosan and HA.

Formation of the Self-assembled Multilayers Containing the Temperature/ pH Dual-responsive Microgels

<P>Background: Stimuli-responsive microgels have attracted extensive investigations due to their potential applications in drug delivery, catalysis, and sensor technology. The self-assembled mcirogel films can contain different functional groups (e.g., -COOH, -NH2, -C=ONH2) to interact with specific molecules and ions in water, and their study is becoming increasingly important for developing both absorbent materials and sensor coatings. This paper is aimed to obtain a better understanding of the LbL multilayer formation of microgels and the branched PEI using the mass sensitive QCM. Additionally the influence of the temperature and pH on the formation of the microgel films can be achieved. </P><P> Methods: The temperature and pH sensitive P(NIPAM-co-AA-co-TMSPMA) microgels were prepared by surfactant-free emulsion polymerization and confirmed by FT-IR, laser particle size analysis, and SEM. The obtained microgel and PEI were further used to prepare multilayer thin films by the LbL self-assembly technique monitored by QCM, and their morphology and hydrophilic properties were determined by AFM and water contact angle measurements. </P><P> Results: The thermosensitive and pH sensitive P(NIPAM-co-AA-co-TMSPMA) microgels were prepared by surfactant-free emulsion polymerization. The size and swelling properties of the microgels prepared are highly dependent on the preparation conditions such as the AA and crosslinker content, and microgels showed good temperature and pH responsive properties. SEM images showed that microgels dispersed evenly on the substrate and had a uniform particle size distribution, which was consistent with the light particle size analysis results. Furthermore, multilayer films composed of the negatively charged microgels and the positively charged PEI have been built up by a facile LbL assembly method and the influence of the deposition conditions on their formation was monitored in real time by QCM. Compared to the temperature of 25 °C, the high temperature of 35°C above the phase transition temperature leads to the more adsorbed mass of microgels on the gold surface of QCM sensors. The absorbed mass values at the deposition pH 7 and 10 are 9.82 and 7.28 µg cm-2, respectively, which are much higher than 1.51 µg cm-2 of the layers deposited at pH 4. The water contact angle and AFM both confirmed the wettability properties and morphology of multilayers on the gold surface of QCM sensors. </P><P> Conclusion: The formation of the multilayer films on the gold surface by the layer-by-layer deposition technique of the negatively charged microgels and the oppositely charged PEI can be achieved. The controllable multilayer formation can be attributed to the size difference, changes in the hydrophilic property and surface charge density of microgels responsive to the external temperature and pH.</P>

A first blue fluorescence composite film based on graphitic carbon nitride nanosheets/polyoxometalate for application in reversible electroluminescence switching

A composite film containing g-C3N4NS and SiMoW was constructed by LBL assembly to realize fluorescence switch regulation.

Stable and self-healable LbL coating with antibiofilm efficacy based on alkylated polyethyleneimine micelles

An antibacterial and self-healing coating was fabricated via LbL assembly based on N-decyl PEI (DPEI) micelles.

Fabrication of silk microcapsules by layer-by-layer desolvation

The procedure to increase shell thickness of multilayer silk microcapsules fabricated by layer-by-layer assembly (LbL assembly) are tedious and time-consuming. To address this, layer-by-layer desolvation (LbL desolvation), a more efficient technique, was developed with PLGA microspheres as sacrificial templates. Due to high efficiency of desolvation in increasing the shell thickness, self-supporting structures were obtained with merely seven silk layers. Permeability of the microcapsules was manipulated with high efficiency as well. Moreover, crosslinking was found to reduce surface charge of the shell. We attributed this to crosslinking-induced conformational change of silk fibroin based on secondary structure analysis. The LbL desolvation technique will facilitate fabrication of multilayer silk microcapsules for biomedical applications.