Ionically Paired Layer-by-Layer Hydrogels: Water and Polyelectrolyte Uptake Controlled by Deposition Time

Metal organic framework/polyelectrolyte composites for water vapor sorption applications

Metal-organic framework (MOF) core particles of MIL-101(Cr), aluminum fumarate (Basolite® A520), MIL-53-TDC, zirconium fumarate, and UiO-66 were modified by adsorption of thin polyelectrolyte (PE)-based shells without deterioration of their crystal structure. By applying different PEs and depositing a single layer (MOF/PE) or one to three layer-by-layer assembled bilayers (MOF/LbL), the mass percent of shell material in the composite was varied from 0.6-2.5% to 50%. Under a constant relative pressure of water vapor, the moisture uptake by a MOF/PE and a MOF/LbL is rather comparable with its S-shaped curvature to that of pristine MOFs. The relevant differences, such as a shift of the ascending adsorption part to lower/higher relative pressure or an increase/decrease in water uptake in selected regions, are associated with the core-shell structure and related to the morphological changes of the MOF powders. The hydrophilic surface promotes the formation of liquid menisci at the points of contact between particles and accelerates the moisture uptake and loss. A decrease in water sorption under an atmosphere with high humidity by some composites can be associated with the inhibition of liquid water condensation by the more hydrophobic shells.

Layer-by-Layer Cell Encapsulation for Drug Delivery: The History, Technique Basis, and Applications

The encapsulation of cells with various polyelectrolytes through layer-by-layer (LbL) has become a popular strategy in cellular function engineering. The technique sprang up in 1990s and obtained tremendous advances in multi-functionalized encapsulation of cells in recent years. This review comprehensively summarized the basis and applications in drug delivery by means of LbL cell encapsulation. To begin with, the concept and brief history of LbL and LbL cell encapsulation were introduced. Next, diverse types of materials, including naturally extracted and chemically synthesized, were exhibited, followed by a complicated basis of LbL assembly, such as interactions within multilayers, charge distribution, and films morphology. Furthermore, the review focused on the protective effects against adverse factors, and bioactive payloads incorporation could be realized via LbL cell encapsulation. Additionally, the payload delivery from cell encapsulation system could be adjusted by environment, redox, biological processes, and functional linkers to release payloads in controlled manners. In short, drug delivery via LbL cell encapsulation, which takes advantage of both cell grafts and drug activities, will be of great importance in basic research of cell science and biotherapy for various diseases.

Polyelectrolyte Gels: Fundamentals, Fabrication and Applications

Polyelectrolyte gels are an important class of polymer gels and a versatile platform with charged polymer networks with ionisable groups. They have drawn significant recent attention as a class of smart material and have demonstrated potential for a variety of applications. This review begins with the fundamentals of polyelectrolyte gels, which encompass various classifications (i.e., origin, charge, shape) and crucial aspects (ionic conductivity and stimuli responsiveness). It further centralises recent developments of polyelectrolyte gels, emphasising their synthesis, structure-property relationships and responsive properties. Sequentially, this review demonstrates how polyelectrolyte gels' flourishing properties create attractiveness to a range of applications including tissue engineering, drug delivery, actuators and bioelectronics. Finally, the review outlines the indisputable appeal, further improvements and emerging trends in polyelectrolyte gels.

Layer-by-Layer Biomaterials for Drug Delivery

Controlled drug delivery formulations have revolutionized treatments for a range of health conditions. Over decades of innovation, layer-by-layer (LbL) self-assembly has emerged as one of the most versatile fabrication methods used to develop multifunctional controlled drug release coatings. The numerous advantages of LbL include its ability to incorporate and preserve biological activity of therapeutic agents; coat multiple substrates of all scales (e.g., nanoparticles to implants); and exhibit tuned, targeted, and/or responsive drug release behavior. The functional behavior of LbL films can be related to their physicochemical properties. In this review, we highlight recent advances in the development of LbL-engineered biomaterials for drug delivery, demonstrating their potential in the fields of cancer therapy, microbial infection prevention and treatment, and directing cellular responses. We discuss the various advantages of LbL biomaterial design for a given application as demonstrated through in vitro and in vivo studies.

Polymer- and Hybrid-Based Biomaterials for Interstitial, Connective, Vascular, Nerve, Visceral and Musculoskeletal Tissue Engineering

In this review, materials based on polymers and hybrids possessing both organic and inorganic contents for repairing or facilitating cell growth in tissue engineering are discussed. Pure polymer based biomaterials are predominantly used to target soft tissues. Stipulated by possibilities of tuning the composition and concentration of their inorganic content, hybrid materials allow to mimic properties of various types of harder tissues. That leads to the concept of "one-matches-all" referring to materials possessing the same polymeric base, but different inorganic content to enable tissue growth and repair, proliferation of cells, and the formation of the ECM (extra cellular matrix). Furthermore, adding drug delivery carriers to coatings and scaffolds designed with such materials brings additional functionality by encapsulating active molecules, antibacterial agents, and growth factors. We discuss here materials and methods of their assembly from a general perspective together with their applications in various tissue engineering sub-areas: interstitial, connective, vascular, nervous, visceral and musculoskeletal tissues. The overall aims of this review are two-fold: (a) to describe the needs and opportunities in the field of bio-medicine, which should be useful for material scientists, and (b) to present capabilities and resources available in the area of materials, which should be of interest for biologists and medical doctors.

Biologically Functional Ultrathin Films Made of Zwitterionic Block Copolymer Micelles

We report the preparation of ultrathin coatings of zwitterionic block copolymer micelles and a comparison of their protein adsorption, adhesiveness, and antibacterial properties. Zwitterionic block copolymer micelles were obtained through pH-induced self-assembly of poly[3-dimethyl(methacryloyloxyethyl)ammonium propanesulfonate- b-2-(diisopropylamino)ethyl methacrylate] (βPDMA- b-PDPA) at pH 7.5. βPDMA- b-PDPA micelles with zwitterionic βPDMA-corona and pH-responsive PDPA-core were then used as building blocks to prepare layer-by-layer (LbL) assembled multilayer films together with hyaluronic acid (HA), tannic acid (TA), or poly(sodium 4-styrenesulfonate) (PSS). Protein adsorption tests showed that 3-layer βPDMA- b-PDPA micelles/HA films were the most effective to reduce the adhesion of BSA, lysozyme, ferritin, and casein. In contrast, βPDMA- b-PDPA micelles/TA films were the most attractive surfaces for protein adsorption. Bacterial antiadhesive tests against a model Gram-negative bacterium, Escherichia coli, and a model Gram-positive bacterium, Staphylococcus aureus, were in good agreement with the protein adsorption properties of the films. The differences in the antiadhesive properties between these three different film systems are discussed within the context of chemical nature and the functional chemical groups of the polyanions, layer number, and surface morphology of the films. Multilayers were found to lose their antiadhesiveness in the long term. However, by taking advantage of the pH-responsive hydrophobic micellar cores, we show that an antibacterial agent could be loaded into the micelles and multilayers could exhibit antibacterial activity in the long term especially at moderately acidic conditions. In contrast to antiadhesive properties, no significant differences were recorded in the antibacterial properties between the different film types.