Poly(ethylene glycol)-poly(L-lactide) star block copolymer hydrogels crosslinked by metal-ligand coordination

Advanced supramolecular hydrogels and their applications in the formulation of next-generation bioinks for tissue engineering: A review

Supramolecular hydrogels are three-dimensional structures composed of cross-linked macromolecules interconnected by dynamic physical bonds, which allow them to absorb and retain significant volumes of water. Their intrinsic properties, such as viscoelasticity, self-healing capabilities, and high water content, render them promising materials for cell-laden scaffolds utilized in bioinks. This review systematically summarizes the current state-of-the-art advancements in hydrogels for tissue engineering, categorizing them based on the nature of their supramolecular interactions. Particular emphasis is placed on the classification of supramolecular hydrogels and their associated properties, including kinetics, mechanical characteristics, responsiveness, and swelling behavior. The review specifically addresses the criteria that hydrogels must fulfill prior to their application in bioinks. Achieving biocompatibility and bioactivity necessitates the careful selection of hydrogel compositions with suitable properties, as well as the incorporation of external organic or inorganic bioactive molecules. Methods for measuring and enhancing biophysical and biochemical properties are discussed in detail, alongside an exploration of the unique requirements of bioinks tailored for each additive manufacturing method. This review paper serves as an instructive resource for the construction and characterization of supramolecular hydrogels, facilitating their application in bioinks for tissue engineering.

One-Pot Reactive Melt Recycling of PLA Post-Consumer Waste for the Production of Block Copolymer Nanocomposites of High Strength and Ductility

Post-consumer waste recycling is a crucial issue for building a sustainable society. However, mechanical recycling of poly(lactic acid) (PLA) often reduces the performance of the recycled material because PLA has a strong tendency to degrade during reprocessing. Therefore, it is of great interest to develop an effective recycling method to improve the mechanical performance of this material. This paper presents a one-pot melt process for turning PLA waste into a biodegradable block copolymer and its high strength and ductility composite. The process was conducted in a melt-mixer through a transesterification of PLA with poly(ethylene glycol) (PEG) or poly(propylene glycol) (PPG) as a soft component and clay as reinforcement. Effects of soft component content and sequence of clay addition on the mechanical performance of the prepared materials were focused. The results showed the successful preparation of PLA-based multiblock copolymers of high molecular weights (~100 kDa). Both virgin PLA and recycled source could serve as the starting material. PEG was more efficient than PPG in providing an intense improvement of PLA ductility. The nanocomposite of intercalated structure yielded nearly 100 times higher elongation at break (E_b = 506%) than the starting PLA (E_b = 5.6%) with high strength of 39.5 MPa and modulus of 1.4 GPa, considering the advantages of clay addition. Furthermore, the products with a broadened range of properties can be designed based on the ratio of PLA and soft component, as well as the organization and spatial distribution of clay in the copolymer matrices.

Green Copolymers Based on Poly(Lactic Acid)-Short Review

Polylactic acid (PLA) is a biodegradable and biocompatible polymer that can be applied in the field of packaging and medicine. Its starting substrate is lactic acid and, on this account, PLA can also be considered an ecological material produced from renewable resources. Apart from several advantages, polylactic acid has drawbacks such as brittleness and relatively high glass transition and melting temperatures. However, copolymerization of PLA with other polymers improves PLA features, and a desirable material marked by preferable physical properties can be obtained. Presenting a detailed overview of the accounts on the PLA copolymerization accomplishments is the innovation of this paper. Scientific findings, examples of copolymers (including branched, star, grafted or block macromolecules), and its applications are discussed. As PLA copolymers can be potentially used in pharmaceutical and biomedical areas, the attention of this article is also placed on the advances present in this field of study. Moreover, the subject of PLA synthesis is described. Three methods are given: azeotropic dehydrative condensation, direct poly-condensation, and ring-opening polymerization (ROP), along with its mechanisms. The applied catalyst also has an impact on the end product and should be adequately selected depending on the intended use of the synthesized PLA. Different ways of using stannous octoate (Sn(Oct)₂) and examples of the other inorganic and organic catalysts used in PLA synthesis are presented.

Soft Materials by Design: Unconventional Polymer Networks Give Extreme Properties

Hydrogels are polymer networks infiltrated with water. Many biological hydrogels in animal bodies such as muscles, heart valves, cartilages, and tendons possess extreme mechanical properties including being extremely tough, strong, resilient, adhesive, and fatigue-resistant. These mechanical properties are also critical for hydrogels' diverse applications ranging from drug delivery, tissue engineering, medical implants, wound dressings, and contact lenses to sensors, actuators, electronic devices, optical devices, batteries, water harvesters, and soft robots. Whereas numerous hydrogels have been developed over the last few decades, a set of general principles that can rationally guide the design of hydrogels using different materials and fabrication methods for various applications remain a central need in the field of soft materials. This review is aimed at synergistically reporting: (i) general design principles for hydrogels to achieve extreme mechanical and physical properties, (ii) implementation strategies for the design principles using unconventional polymer networks, and (iii) future directions for the orthogonal design of hydrogels to achieve multiple combined mechanical, physical, chemical, and biological properties. Because these design principles and implementation strategies are based on generic polymer networks, they are also applicable to other soft materials including elastomers and organogels. Overall, the review will not only provide comprehensive and systematic guidelines on the rational design of soft materials, but also provoke interdisciplinary discussions on a fundamental question: why does nature select soft materials with unconventional polymer networks to constitute the major parts of animal bodies?

Fine-Tuning Crystallization-Induced Gelation in Amphiphilic Double-Brush Polymers

A series of amphiphilic double-brush polymers based on itaconate diesters were synthesized with the objective of tailoring the thermal and mechanical properties of hydrogels formed by them; the amphiphilic itaconate diesters carried an MPEG350 segment and an alkyl chain, whose length was varied from C12 to C18. As was reported by us earlier (Macromolecules 2017, 50, 5004), the formation of the hydrogel was due to the crystallization of alkyl segments, as confirmed by the match of the rheological gel-to-sol transition with that of differential scanning calorimetry melting transition of the gel. In an effort to fine-tune the hydrogel-melting temperature and its strength, we varied the length of the alkyl chain length while keeping the hydrophilic segment length constant at MPEG350; apart from varying the alkyl chain length, an oxyethylene spacer was incorporated to examine the effect of decoupling the alkyl side-chain crystallization from the backbone. With these modifications, the melting temperature of the hydrogel was varied from 30 to 56 °C. Likewise, the strength of the hydrogel, as reflected by its storage modulus, varied from around 220 to 970 Pa; the softer gels typically exhibited a slightly larger critical shear strain beyond which the gel transformed into a sol. The thermal and shear-induced gel-to-sol transitions were reversible; however, the modulus after the shear-induced transition did not fully recover instantly (∼80%), suggesting that the formation of the extended gel network is slow. Further fine-tuning could be achieved by copolymerization of two different amphiphilic itaconate monomers, namely, those with C16 and C18, which provided an intermediate gel-melting temperature; however, co-gelation of the two preformed homopolymer gels yielded two distinct gel-melting transitions. Thus, this class of tuneable stimuli-responsive polymeric hydrogels prepared from biobenign components, namely, itaconic acid, 1-alkanols, and MPEGs, could serve as potential candidates for biomedical applications.

Di(2-picolyl)amine-functionalized poly(ethylene glycol) hydrogels with tailorable metal–ligand coordination crosslinking

A new class of metallo-hydrogels has been developed using di(2-picolyl)amine (DPA)-functionalized 4-arm polyethylene glycol (4A-PEG-DPAn) polymers crosslinked by metal–ligand coordination.

Recent advances in the development of gene delivery systems

Background

Gene delivery systems are essentially necessary for the gene therapy of human genetic diseases. Gene therapy is the unique way that is able to use the adjustable gene to cure any disease. The gene therapy is one of promising therapies for a number of diseases such as inherited disorders, viral infection and cancers. The useful results of gene delivery systems depend open the adjustable targeting gene delivery systems. Some of successful gene delivery systems have recently reported for the practical application of gene therapy.

Main body

The recent developments of viral gene delivery systems and non-viral gene delivery systems for gene therapy have briefly reviewed. The viral gene delivery systems have discussed for the viral vectors based on DNA, RNA and oncolytic viral vectors. The non-viral gene delivery systems have also treated for the physicochemical approaches such as physical methods and chemical methods. Several kinds of successful gene delivery systems have briefly discussed on the bases of the gene delivery systems such as cationic polymers, poly(L-lysine), polysaccharides, and poly(ethylenimine)s.

Conclusion

The goal of the research for gene delivery system is to develop the clinically relevant vectors such as viral and non-viral vectors that use to combat elusive diseases such as AIDS, cancer, Alzheimer, etc. Next step research will focus on advancing DNA and RNA molecular technologies to become the standard treatment options in the clinical area of biomedical application.

Self-Healing Polymeric Hydrogel Formed by Metal-Ligand Coordination Assembly: Design, Fabrication, and Biomedical Applications

Self-healing hydrogels based on metal-ligand coordination chemistry provide new and exciting properties that improve injectability, rheological behaviors, and even biological functionalities. The inherent reversibility of coordination bonds improves on the covalent cross-linking employed previously, allowing for the preparation of completely self-healing hydrogels. In this article, recent advances in the development of this class of hydrogels are summarized and their applications in biology and medicine are discussed. Various chelating ligands such as bisphosphonate, catechol, histidine, thiolate, carboxylate, pyridines (including bipyridine and terpyridine), and iminodiacetate conjugated onto polymeric backbones, as well as the chelated metal ions and metal ions containing inorganic particles, which are used to form dynamic networks, are highlighted. This article provides general ideas and methods for the design of self-healing hydrogel biomaterials based on coordination chemistry.

Synthesis of a metal-coordinated N-substituted polybenzimidazole pyridine sulfone and method for the nondestructive analysis of thermal stability

N-substituted metal-coordinated cross-linking polybenzimidazole pyridine sulfone, as novel class of high-performance functional polymers, has been obtained by the coordination of N-substituted polybenzimidazole pyridine sulfone (Py-N-PBIS) ligand with varying content of metallic ion (Co2+, Ni2+, Zn2+). The structures of the polymers are characterized by means of fourier transform infrared spectroscopy (FT-IR) and 1H nuclear magnetic resonance (1H NMR) spectroscopy, the results show good agreement with the proposed structures. Thermogravimetric analysis measurements exhibit that the metal coordination polymers possess good thermal stability with high thermal decomposition temperature (thermally stable up to 405–510°C). More importantly, the thermal decomposition temperature of Py-N-PBIS-(Co2+, Ni2+, Zn2+) can be nondestructively detected by taking advantage of the fluorescence quenching effect of metal coordination to 2,6-Bis(2-benzimidazolyl)pyridine structure.

Copper-based hydrogels with dicarboxylate spacer ligands for selective carbon dioxide separation applications

Dicarboxylate spacer ligands enhanced the rigidity, porosity, surface area, and CO₂/N₂ and CO₂/CH₄ selectivity of Cu²⁺-based poly(methyl vinyl ether-alt-maleic anhydride) hydrogels.

Supramolecular polymer networks: hydrogels and bulk materials

Supramolecular polymer networks are materials crosslinked by reversible supramolecular interactions, such as hydrogen bonding or electrostatic interactions. Supramolecular materials show very interesting and useful properties resulting from their dynamic nature, such as self-healing, stimuli-responsiveness and adaptability. Here we will discuss recent progress in polymer-based supramolecular networks for the formation of hydrogels and bulk materials.

Sol–gel reversible metallo-supramolecular hydrogels based on a thermoresponsive double hydrophilic block copolymer

A new thermoresponsive double hydrophilic block copolymer bearing a terpyridine moiety formed a hydrogel with a sol–gel thermoreversible transition in the presence of Fe²⁺ ions.

Injectable supramolecular hydrogels fabricated from PEGylated doxorubicin prodrug and α-cyclodextrin for pH-triggered drug delivery

Fabrication of in situ forming and acid-labile prodrug-based supramolecular hydrogels with adjustable gelation time for injectable drug delivery carriers.

A pH-sensitive and biodegradable supramolecular hydrogel constructed from a PEGylated polyphosphoester-doxorubicin prodrug and α-cyclodextrin

Fabrication of in situ forming supramolecular hydrogels based on an acid-labile and PEGylated polyphosphoester-doxorubicin prodrug for injectable drug delivery carriers.

Synthesis, characterization and cyclic voltammetric study of copper(II) and nickel(II) polymer chelates

Graft copolymers based on dextran (Dx) and 2-acrylamido-2-methyl-1-propane sulphonic acid (AMPS) were synthesized by free radical initiated solution polymerization technique using ceric ammonium nitrate as initiator. These graft copolymers were used to prepare Cu(II) and Ni(II) chelates by reactions with Cu(II) and Ni(II) metal ions respectively. Graft copolymer and metal chelates were characterized by elemental analysis, intrinsic viscosity, FT-IR, scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA) and powder X-ray diffraction (XRD). Elemental analysis, intrinsic viscosity and FT-IR studies revealed the incorporation of metal ions to form metal chelates. SEM studies showed the change in morphology due to metal incorporation. From AFM studies it was observed that there was increase in Root mean square (RMS) roughness values in case of metal complexes. Metal chelates were observed to be thermally more stable than graft copolymer from TGA. UV-vis spectroscopy study revealed increase in absorbance values and cyclic voltammetric (CV) studies showed more than tenfold increase in redox current due to formation of Cu(II) and Ni(II) metal chelates. The binding constants of each complex determined by using UV-visible spectroscopy revealed that Cu(II) has more binding ability than Ni(II).

Dynamic self-assembly of coordination polymers in aqueous solution

The construction of supramolecular polymers has been intensively pursued because the nanostructures formed through weak non-covalent interactions can be triggered by external stimuli leading to smart materials and sensors. Self-assemblies of coordination polymers consisting of metal ions and organic ligands in aqueous solution also provide particular contributions in this area. The main motivation for developing those coordination polymers originates from the value-added combination between metal ions and ligands. This review highlights the recent progress of the dynamic self-assembly of coordination polymers that result from the sophisticated molecular design, towards fabricating stimuli-responsive systems and bio-related materials. Dynamic structural changes and switchable physical properties triggered by various stimuli are summarized. Finally, the outlook for aqueous nanostructures originated from the dynamic self-assembly of coordination polymers is also presented.

Photocatalytic reactions of a nickel(ii) annulene complex incorporated in polymeric structures

A study of the structural and chemical processes of a new polymeric photocatalyst containing a Ni(ii) macrocyclic complex and its application to the solar reduction of CO₂ in aqueous homogeneous solution.