Engineering the Extracellular Environment: Strategies for Building 2D and 3D Cellular Structures

Cell fate is regulated by extracellular environmental signals. Receptor specific interaction of the cell with proteins, glycans, soluble factors as well as neighboring cells can steer cells towards proliferation, differentiation, apoptosis or migration. In this review, approaches to build cellular structures by engineering aspects of the extracellular environment are described. These methods include non‐specific modifications to control the wettability and stiffness of surfaces using self‐assembled monolayers (SAMs) and polyelectrolyte multilayers (PEMs) as well as methods where the temporal activation and spatial distribution of adhesion ligands is controlled. Building on these techniques, construction of two‐dimensional cell sheets using temperature sensitive polymers or electrochemical dissolution is described together with current applications of these grafts in the clinical arena. Finally, methods to pattern cells in three‐dimensions as well as to functionalize the 3D environment with biologic motifs take us one step closer to being able to engineer multicellular tissues and organs.     

Solvent-assisted patterning of polyelectrolyte multilayers and selective deposition of virus assemblies

We introduce a simple method to pattern electrostatic assemblies of viruses onto a polyelectrolyte multilayer. The increased mobility of weak polycation chains in the multilayer above a given thickness ensures the surface mobility of viruses required for spontaneous ordering of densely packed viruses atop polymeric patterns. To pattern the polyelectrolyte multilayer film, we employ a nonconventional patterning method known as solvent-assisted capillary molding for the first time on multilayer films, and demonstrate micrometer-scaled dense patterns of viruses, where the accessible feature size can be correlated by the length scale of virus and swelling property of underlying patterned polyelectrolyte multilayer. We further examine the ability to modify the top surfaces of these assemblies with biological ligands, which extends the applicability of patterned viruses to biological detection purposes. We expect that the present method described here can be generally applied to the patterning of other polyelectrolyte multilayers and combined with the ordered assembly of anisotropic nanomaterials such as polymeric nanotubes or inorganic nanowires for a broad range of applications.     

Kinetic modulation of pulsed chronopotentiometric polymeric membrane ion sensors by polyelectrolyte multilayers

Polymeric membrane ion-selective electrodes are normally interrogated by zero current potentiometry, and their selectivity is understood to be primarily dependent on an extraction/ion-exchange equilibrium between the aqueous sample and polymeric membrane. If concentration gradients in the contacting diffusion layers are insubstantial, the membrane response is thought to be rather independent of kinetic processes such as surface blocking effects. In this work, the surface of calcium-selective polymeric ion-selective electrodes is coated with polyelectrolyte multilayers as evidenced by zeta potential measurements, atomic force microscopy, and electrochemical impedance spectroscopy. Indeed, such multilayers have no effect on their potentiometric response if the membranes are formulated in a traditional manner, containing a lipophilic ion exchanger and a calcium-selective ionophore. However, drastic changes in the potential response are observed if the membranes are operated in a recently introduced kinetic mode using pulsed chronopotentiometry. The results suggest that the assembled nanostructured multilayers drastically alter the kinetics of ion transport to the sensing membrane, making use of the effect that polyelectrolyte multilayers have different permeabilities toward ions with different valences. The results have implications to the design of chemically selective ion sensors since surface-localized kinetic limitations can now be used as an additional dimension to tune the operational ion selectivity.     

Femtomolar electrochemical detection of DNA hybridization using hollow polyelectrolyte shells bearing silver nanoparticles

The preparation, and use as electrochemical labels, of polyelectrolyte shells bearing Ag nanoparticles is described. Their potential for highly sensitive detection is demonstrated. The shells are prepared by layer-by-layer self-assembly around templates (500 nm diameter) which are then dissolved. The shells can be opened and closed by adjustment of solution pH, and this process is utilized to encapsulate Ag nanoparticles, chiefly by adsorption to the inner walls of the capsules. Based on absorbance, TEM and voltammetric measurements, the highest loading achieved is approximately 78 Ag particles per capsule. The Ag capsules are used via biotin-avidin binding as labels for the detection of DNA hybridization, following acid dissolution and then detection of the Ag (+) by ASV. A 30-mer sequence specific to Escherichia coli is measured at DNA-modified screen-printed electrodes with a detection limit of approximately 25 fM, which corresponds to the detection of 4.6 fg ( approximately 3 x 10 (5) molecules) in the 20 microL analyte sample. A 200 fM target containing a single mismatch gives a significantly (<74%) lower response than 200 fM of complementary target; 60 pM of noncomplementary target gives a negligible response.     

The preparation and evaluation of salt forms of linogliride with reduced solubilities as candidates for extended release

Salts of linogliride with reduced solubilities were prepared and evaluated as potential candidates for extended-release oral dosage forms. A once-daily dose of 300–800?mg was intended. Seven acids were selected: p-acetamidobenzoic, benzoic, p-hydroxybenzoic, 3-hydroxy-2-naphthoic, 1-napsylic, pamoic, and p-toluenesulfonic acids but only four salts were able to be prepared in suitable quantities for evaluation: linogliride pamoate, p-hydroxybenzoate, 3-hydroxy-2-naphthoate, and 1-napsylate. The pH-solubility profiles of the four new salts, free base, and fumarate salt were compared over the pH 1.43–8.3 range and the intrinsic dissolution rates of the four new salts and the free base were determined at pH 1.43, 4.4, and 7.5. The range of the pH-solubility profile and intrinsic dissolution rates of the p-hydroxybenzoate salt were less than the free base and fumarate and higher than the other three new salts. The pH-solubilities and intrinsic dissolution rates of the 1-napsylate salt were pH-independent. The solubilities and intrinsic dissolution rates of the pamoate and 3-hydroxy-2-naphthoate were higher at pH 1.4–3.4 than at higher pH. At pH 4.4 and higher, the solubilities were essentially the same, in the 1–2?mg/mL range. The intrinsic dissolution rates were also very low and not very different. Dissolution studies with capsules containing 800?mg doses of the pamoate, 1-napsylate, free base, and fumarate performed in a dissolution medium of pH beginning at 2.2 and ending at 6.8 demonstrated that the pamoate and 1-napsylate salt forms dissolved slower and could be useful as extended-release forms.     

Comparison of dissolution profiles for albendazole tablets using USP apparatus 2 and 4

The in vitro dissolution of albendazole from three different commercially available products (200 mg tablets) was studied using U.S. Pharmacopeia (USP) Apparatus 2 and USP Apparatus 4 in order to compare the release performance of the drug in two essentially different dissolution systems. For both cases, 0.1 N HCl was used as dissolution medium. Only the reference product and one of the generic products studied met the 80% USP 24 specification for albendazole dissolved at 30 min, using USP Apparatus 2. Although the reference product reached 80% of albendazole dissolved at 30 min when Apparatus 4 was used, the generic products' dissolution performance was markedly reduced in this system. Though dissolution rate was slower using Apparatus 4, the total quantity of albendazole dissolved from the reference product, represented by area under the dissolution profile, was practically the same regardless of the system used. Dissolution kinetics of albendazole was adequately described by Weibull's function for all the products. The dissolution time (t_d) derived from data fitting to this function showed significant differences among the products studied. Data analysis based on analysis of variance (ANOVA) showed nonequivalence among the dissolution profiles of generic products compared with the reference product either with the dissolution vessel system or the flow-through cell, as well as nonequivalence among the dissolution profiles using both apparatuses with the same product. Though differences in the dissolution profiles for generic products against the reference product in both systems were found, USP Apparatus 4 showed higher discriminative capacity in differentiating the release characteristics of the products tested.     

Probing the stability of biocompatible sodium hyaluronate/chitosan nanocoatings against changes in salinity and pH

The stability of polyelectrolyte multilayer assemblies was investigated with emphasis on the effects of solution ionic strength, pH, and polymer molecular weight on the film thickness and surface topography. The multilayers consisting of two polysaccharides, the polyanion sodium hyaluronate (HA) and the polycation chitosan (CH) were studied using surface plasmon resonance (SPR) spectroscopy, impedance quartz crystal microbalance (QCM), and atomic force microscopy (AFM). SPR/QCM experiments show that coatings consisting of four HA/CH bilayers assembled at pH 4.5 in the presence of 0.15 M NaCl are stable in NaCl solutions of concentration less than 0.8 M. These multilayers are stable when placed in contact with aqueous solutions ranging in pH from 3.5 to 9. The molecular weight of the polysaccharides has only a marginal effect on the stability of the films in the range explored here (HA: Mn = 360,000 or 31,000 g/mol; CH: Mn = 160,000 or 30,000 g/mol). AFM imaging reveals that different mechanisms may account for the multilayers stability versus salt and pH treatments. While increasing the ionic strength induces reorganization of the surface topography from isolated spherical islets to elongated worm-like features, changes in pH have no appreciable effects on the coating topography prior to complete disintegration.     

Self‐Assembly of Immune Signals Improves Codelivery to Antigen Presenting Cells and Accelerates Signal Internalization,Processing Kinetics,and Immune Activation

Vaccines and immunotherapies that elicit specific types of immune responses offer transformative potential to tackle disease. The mechanisms governing the processing of immune signals—events that determine the type of response generated—are incredibly complex. Understanding these processes would inform more rational vaccine design by linking carrier properties, processing mechanisms, and relevant timescales to specific impacts on immune response. This goal is pursued using nanostructured materials—termed immune polyelectrolyte multilayers—built entirely from antigens and stimulatory toll‐like receptors agonists (TLRas). This simplicity allows isolation and quantification of the rates and mechanisms of intracellular signal processing, and the link to activation of distinct immune pathways. Each vaccine component is internalized in a colocalized manner through energy‐dependent caveolae‐mediated endocytosis. This process results in trafficking through endosome/lysosome pathways and stimulation of TLRs expressed on endosomes/lysosomes. The maximum rates for these events occur within 4 h, but are detectable in minutes, ultimately driving downstream proimmune functions. Interestingly, these uptake, processing, and activation kinetics are significantly faster for TLRas in particulate form compared with free TLRa. Our findings provide insight into specific mechanisms by which particulate vaccines enhance initiation of immune response, and highlight quantitative strategies to assess other carrier technologies.     

Fullerene-functionalized gold nanoparticles: electrochemical and spectroscopic properties

Fullerene (C(60))-tethered gold nanoparticles were synthesized by the coupling of the fullerene molecules with peripheral amine moieties on the particle surface. The particle composition was determined by thermogravimetric analysis and FT-IR spectroscopy. The resulting particles exhibited unique optical and electrochemical properties. UV-visible measurements showed that the C(60) characteristic absorption remained practically invariant whereas the fluorescence demonstrated rather drastic enhancement of emission efficiency as compared to the behaviors of C(60) monomers. Tethering of C(60) on the particle surface has virtually no effect on the particle molecular capacitance when C(60) is in neutral state, whereas when C60 is electroreduced, the particle effective capacitance increases drastically, reflected in the quantized capacitance charging measurements. The strong affinity of C(60) to amine moieties was also exploited to assemble multilayers of C(60) and gold particle nanocomposite structures. Quartz crystal microbalance measurements showed quite efficient adsorption of C(60) and particles up to two repeated cycles. However, the voltammetric responses of the surface-confined C(60) and gold particle composite structures were found to be complicated by the inaccessibility of electrolyte counterions due to the compact nature of the surface assemblies.     

Effect of Granulating Method on Dissolution Rate of Compressed Tablets. III

The dissolution rates of dexamethasone granules prepared by all the methods were slower than the dissolution rates of the corresponding tablets. This was shown to be the result of a reduction of the average particle size on compaction. The dissolution rates of sulfadiazine tablets prepared by microgranulating and slugging were slower than the corresponding granules. This was demonstrated to be the result of enlargement of the granules on compaction. For both drugs the microgranulating procedure gave the most rapid dissolution of tablets and granules. In case of the dexamethasone formulation, direct compression exhibited the slowest dissolution rate. The dissolution rates of sulfadiazine granules and tablets prepared by the wet granulating method were also unsatisfactory.     

Effect of Granulating Method on Dissolution Rate of Compressed Tablets. III

Abstract

The dissolution rates of dexamethasone granules prepared by all the methods were slower than the dissolution rates of the corresponding tablets. This was shown to be the result of a reduction of the average particle size on compaction. The dissolution rates of sulfadiazine tablets prepared by microgranulating and slugging were slower than the corresponding granules. This was demonstrated to be the result of enlargement of the granules on compaction. For both drugs the microgranulating procedure gave the most rapid dissolution of tablets and granules. In case of the dexamethasone formulation, direct compression exhibited the slowest dissolution rate. The dissolution rates of sulfadiazine granules and tablets prepared by the wet granulating method were also unsatisfactory.     

Alternate drop coating for forming dual biointerfaces composed of polyelectrolyte multilayers

Two types of polyelectrolyte multilayers were formed on both sides of a quartz crystal microbalance (QCM) substrate by a novel alternate drop coating process. In this study, poly(diallyldimethylammonium chloride) (PDDA) and poly(sodium 4-styrene sulfonate) (PSS) were used as strong-strong polyelectrolytes. On the other hand, PDDA and poly(acrylic acid) (PAA) were used as strong-weak polyelectrolytes. The novel alternate drop coating process can separately fabricate each polyelectrolyte multilayer on both sides of the substrate. The substrate provides dual biointerfaces, both sides of which comprise different multilayers, by employing a combination of polymers. The formation of the multilayer by alternate drop coating was evaluated in terms of changes in the frequency of the QCM and model protein adsorption for proteins such as bovine serum albumin, and their characteristics were investigated with those of the conventional alternate adsorption process by performing dip coating. There was no significant difference between the surface properties resulting from the two formation conditions. This result strongly supported the fact that the multilayers fabricated by alternate drop coating were similar in quality to those fabricated by conventional dip coating. The resulting dual biointerfaces with polyelectrolyte multilayers provide alternative biofunctions in terms of individual protein loading. In summary, the novel alternate drop coating process for substrates is a good candidate for the preparation of dual biointerfaces in the biomedical field.     

Electrochemical dissolution of Тс–Ru alloys in nitric acid solutions

Electrochemical dissolution of Тс–19 wt % Ru, Тс–45 wt % Ru, and Тс–70 wt % Ru in 1 to 6 M HNO₃ solutions in the amperostatic mode was studied. In the solutions formed from anodic dissolution of Тс–Ru alloys, Ru is present in the form of Ru(IV), and Тс, in the form of Тс(VII). A kinetic study of the electrochemical dissolution of the Тс–70 wt % Ru alloy in the examined interval of HNO₃ concentrations showed that the alloy dissolved congruently and the Тс(VII) and Ru(IV) accumulation in the solution linearly depended on time. Anodic dissolution of Tc–Ru alloys with lower Ru content was also characterized by a linear increase in the Тс(VII) concentration in the solution with time. On the other hand, formation of poorly soluble hydrated Ru(IV) oxide on the electrode surface was observed simultaneously with accumulation of soluble Ru(IV) species in solution. The rate of electrochemical dissolution of the Тс–70 wt % Ru alloy linearly increased with increasing HNO₃ concentration. The rates of electrochemical dissolution of Tc, determined for alloys with lower Ru content, were independent of the HNO₃ concentration in the electrolyte. Oxidation of water with the evolution of oxygen on the surface of Tc–Ru alloys was observed simultaneously with the anodic dissolution of Tc and Ru. This process leads to a decrease in the current efficiency of the Tc and Ru dissolution. Examination of the corrosion damage of the working electrode surfaces by scanning electron microscopy shows that the electrochemical dissolution of Tc–Ru alloys leads to uniform corrosion of their surface.     

不同pH条件下再生纤维表面的CPAM/CMC静电逐层自组装

利用静电逐层自组装技术,在再生纤维表面沉积了阳离子聚丙烯酰胺（CPAM）/羧甲基纤维素（CMC）复合膜。研究了不同pH条件下CPAM/CMC在再生纤维表面的静电吸附规律。采用FT-IR、SEM和Zeta电位测试对再生纤维表面的聚电解质多层膜进行表征,而再生纤维力学性能用纸页的裂断长和耐破指数来评价。研究表明,CPAM/...     

Selectively Promoting or Preventing Osteoblast Growth on Titanium Functionalized with Polyelectrolyte Multilayers

Titanium plays an important role in medical applications, such as hip joint implants or fixation plates. These implants must perform differently depending on their clinical application. In particular, the osseointegrative properties required of the implant vary with clinical application. The present work is aimed at the functionalization of titanium surface using polyelectrolyte multilayers consisting of natural biopolymers and testing their cell adhesive properties with respect to the osseointegration capacity. Multilayered coatings were created from chitosan (Chi), hyaluronic acid (HA), and gelatine (Gel) through layer‐by‐layer deposition. Cell adhesion, proliferation, and viability were tested in vitro with the human osteoblast cell line CAL‐72 at timescales up to 7 d. Two multilayer coatings consisting of alternated chitosan/gelatin or chitosan/hyaluronic acid layers with the outmost layer of gelatin (Chi/Gel) or hyaluronic acid (Chi/HA), respectively, were tested. The experimental results showed that surfaces functionalized with Chi/Gel and Chi/HA multilayers demonstrated a good initial adhesion of osteoblasts. After 4 d culturing, osteoblast cells were almost completely detached from the substrates functionalized with Chi/HA multilayers. In contrast to Chi/HA, the proliferation of osteoblasts on substrates with Chi/Gel multilayer coatings was statistically significantly higher compared to the control titanium. We have shown that the growth of osteoblasts can be enhanced or completely prevented on a titanium surface functionalized with polyelectrolyte multilayers consisting of natural biopolymers, as desired. Both multilayer coatings, Chi/Gel and Chi/HA, have potential for applications in the field of titanium implants, where rapid osseointegration is essential, and/or where no ingrowth of the implant is desired, respectively.     

The use of controlled copper dissolution as an anti-fouling system

The use of copper as an anti-fouling surface is discussed and an electrochemical method for improving its performance is proposed. Seawater exposure trials of freely corroding, cathodically protected and electrochemically controlled copper specimens are described. The results show that the anti-fouling performance of copper surfaces may be improved by electrochemical control of its dissolution rates. The ultimate failure of the copper to anti-foul is due to insufficient dissolution rates. This may be due to electrochemical constraints, to the formation of insoluble corrosion products or to the precipitation of cathodic chalks at its surface.     

膜模拟化学在纳米材料中的应用研究

论述了膜模拟化学在纳米材料中的应用研究,介绍了由表面活性剂或磷脂形成的有序组合体的结构和特征,利用反相胶束,微乳、泡囊,聚离子以及单分子层和多分子层制备了纳米材料,其中包括纳米颗粒,单颗粒膜和无机有机复合膜,评论这些纳米材料的结构和性质。     

A Paradigm Shift from 2D to 3D: Surface Supramolecular Assemblies and Their Electronic Properties Explored by Scanning Tunneling Microscopy and Spectroscopy (Small 24/2023)

Exploring supramolecular architectures at surfaces plays an increasingly important role in contemporary science, especially for molecular electronics. A paradigm of research interest in this context is shifting from 2D to 3D that is expanding from monolayer, bilayers, to multilayers. Taking advantage of its high-resolution insight into monolayers and a few layers, scanning tunneling microscopy/spectroscopy (STM/STS) turns out a powerful tool for analyzing such thin films on a solid surface. This review summarizes the representative efforts of STM/STS studies of layered supramolecular assemblies and their unique electronic properties, especially at the liquid–solid interface. The superiority of the 3D molecular networks at surfaces is elucidated and an outlook on the challenges that still lie ahead is provided. This review not only highlights the profound progress in 3D supramolecular assemblies but also provides researchers with unusual concepts to design surface supramolecular structures with increasing complexity and desired functionality.     

Effect of pH on Theophylline Release from Partially Esterifted Alginic Acid Matrices

The effect of dissolution medium pH on theophylline release from co-compressed matrices composed of a 40% benzyl ester of alginic acid was investigated using both the USP rotating paddle method and a modification of the USP rotating basket method. Release rates for each pH were compared using a measure of the time for approximately 80% release (t80%). Results show release of theophylline from these matrices to be significantly slower at pH 1 than at pH 2 and above. Beyond pH 2, drug release is relatively insensitive to dissolution medium pH but is affected by dissolution method because of the tendency of the alginate to form an adhesive, gel-like layer at pH values higher than four. The drug release characteristics of this polymer, under various pH conditions, make it potentially suitable for use in delayed/controlled release oral delivery systems containing compounds that are acid labile or irritating to the gastric mucosa.     

Effect of pH on Theophylline Release from Partially Esterifted Alginic Acid Matrices

The effect of dissolution medium pH on theophylline release from co-compressed matrices composed of a 40% benzyl ester of alginic acid was investigated using both the USP rotating paddle method and a modification of the USP rotating basket method. Release rates for each pH were compared using a measure of the time for approximately 80% release (t80%). Results show release of theophylline from these matrices to be significantly slower at pH 1 than at pH 2 and above. Beyond pH 2, drug release is relatively insensitive to dissolution medium pH but is affected by dissolution method because of the tendency of the alginate to form an adhesive, gel-like layer at pH values higher than four. The drug release characteristics of this polymer, under various pH conditions, make it potentially suitable for use in delayed/controlled release oral delivery systems containing compounds that are acid labile or irritating to the gastric mucosa.