Poly(ethylene glycol)s With a Single Cinnamaldehyde Acetal Unit for Fabricating Acid-Degradable Hydrogel

A synthetic route to prepare a poly(ethylene glycol) with a single cinnamaldehyde acetal unit in the polymer chain, was successfully established using a newly synthesized cinnamaldehyde acetal diethylene glycol (CADEG) as initiator. This HO-PEG(ca)-OH is non-toxic and would be degraded into a cinnamaldehyde and two PEG diols in acid environment. A whole polyethylene glycol based hydrogel was easily fabricated by thiol-ene “click” reaction in alkalescence aqueous solution using acrylate-PEG(ca)-acrylate and 4-arm PEG-SH as raw materials at room temperature. The gel time was dependent on the pH of the solution and its alkalinity can promote gel. The hydrogel can be degradable in acidic conditions and the stronger the acidity, the faster the degradation. This HO-PEG(ca)-OH also can be used in synthesis of cinnamaldehyde containing PEG derivatives, block copolymers or other acid degradable materials.

Preparation of a mimetic and degradable poly(ethylene glycol) by a non-eutectic mixture of organocatalysts (NEMO) via a one-pot two-step process

A one-pot, two-step method for the preparation of degradable PEG is here presented. The full process addresses the requirements imposed by green chemistry and involves the use of a single and nontoxic non-eutectic mixture of organocatalysts. The strategy relies on the polycondensation of PEG800 after its functionalization by bio-derived 5-membered γ-butyrolactone.

A one-pot, two-step method for the preparation of degradable PEG is here presented.

Degradable poly(ethylene oxide) through metal-free copolymerization of ethylene oxide with l-lactide

A simple and convenient method for the preparation of degradable poly(ethylene oxide) (PEO) is presented in this work.

Biodegradable dendrimers for drug delivery

Dendrimers, as a type of artificial polymers with unique structural features, have been extensively explored for their applications in biomedical fields, especially in drug delivery. However, one important concern about the most commonly used dendrimers exists - the nondegradability, which may cause side effects induced by the accumulation of synthetic polymers in cells or tissues. Therefore, biodegradable dendrimers incorporating biodegradability with merits of dendrimers such as well-defined architectures, copious internal cavities and surface functionalities, are much more promising for developing novel nontoxic drug carriers. Herein, we review the recent advances in design and synthesis of biodegradable dendrimers, as well as their applications in fabricating drug delivery systems, with the aim to provide researchers in the related fields a good understanding of biodegradable dendrimers for drug delivery.

Polymerization of Ethylene Oxide, Propylene Oxide, and Other Alkylene Oxides: Synthesis, Novel Polymer Architectures, and Bioconjugation

The review summarizes current trends and developments in the polymerization of alkylene oxides in the last two decades since 1995, with a particular focus on the most important epoxide monomers ethylene oxide (EO), propylene oxide (PO), and butylene oxide (BO). Classical synthetic pathways, i.e., anionic polymerization, coordination polymerization, and cationic polymerization of epoxides (oxiranes), are briefly reviewed. The main focus of the review lies on more recent and in some cases metal-free methods for epoxide polymerization, i.e., the activated monomer strategy, the use of organocatalysts, such as N-heterocyclic carbenes (NHCs) and N-heterocyclic olefins (NHOs) as well as phosphazene bases. In addition, the commercially relevant double-metal cyanide (DMC) catalyst systems are discussed. Besides the synthetic progress, new types of multifunctional linear PEG (mf-PEG) and PPO structures accessible by copolymerization of EO or PO with functional epoxide comonomers are presented as well as complex branched, hyperbranched, and dendrimer like polyethers. Amphiphilic block copolymers based on PEO and PPO (Poloxamers and Pluronics) and advances in the area of PEGylation as the most important bioconjugation strategy are also summarized. With the ever growing toolbox for epoxide polymerization, a "polyether universe" may be envisaged that in its structural diversity parallels the immense variety of structural options available for polymers based on vinyl monomers with a purely carbon-based backbone.

Biodegradable pH-Sensitive Poly(ethylene glycol) Nanocarriers for Allergen Encapsulation and Controlled Release

In the last decades, the number of allergic patients has increased dramatically. Allergen-specific immunotherapy (SIT) is the only available cause-oriented therapy so far. SIT reduces the allergic symptoms, but also exhibits some disadvantages; that is, it is a long-lasting procedure and severe side effects like anaphylactic shock can occur. In this work, we introduce a method to encapsulate allergens into nanoparticles to avoid severe side effects during SIT. Degradable nanocarriers combine the advantage of providing a physical barrier between the encapsulated cargo and the biological environment as well as responding to certain local stimuli (like pH) to release their cargo. This work introduces a facile strategy for the synthesis of acid-labile poly(ethylene glycol) (PEG)-macromonomers that degrade at pH 5 (physiological pH inside the endolysosome) and can be used for nanocarrier synthesis. The difunctional, water-soluble PEG dimethacrylate (PEG-acetal-DMA) macromonomers with cleavable acetal units were analyzed with 1H NMR, SEC, and MALDI-ToF-MS. Both the allergen and the macromonomers were entrapped inside liposomes as templates, which were produced by dual centrifugation (DAC). Radical polymerization of the methacrylate units inside the liposomes generated allergen-loaded PEG nanocarriers. In vitro studies demonstrated that dendritic cells (DCs) internalize the protein-loaded, nontoxic PEG-nanocarriers. Furthermore, we demonstrate by cellular antigen stimulation tests that the nanocarriers effectively shield the allergen cargo from detection by immunoglobulins on the surface of basophilic leucocytes. Uptake of nanocarriers into DCs does not lead to cell maturation; however, the internalized allergen was capable to induce T cell immune responses.

Efficient and economical synthesis of dendrimer-like polystyrene with long subchains through arm-first divergent strategy

Arm-first divergent approach combined with selective precipitation has been developed to synthesize dendrimer-like polystyrenes efficiently and economically.

Branched Acid-Degradable, Biocompatible Polyether Copolymers via Anionic Ring-Opening Polymerization Using an Epoxide Inimer

The introduction of acid-degradable acetal moieties into a hyperbranched polyether backbone has been achieved by the design of a novel epoxide-based degradable inimer. This new monomer, namely, 1-(glycidyloxy)ethyl ethylene glycol ether (GEGE), has been copolymerized in the anionic ring-opening polymerization (AROP) with ethylene oxide (EO) or glycidol (G), respectively, yielding branched polyethers, that is, P(EO-co-GEGE) and P(G-co-GEGE), that possess an adjustable amount of acid-cleavable acetal units. In addition, a novel class of multiarm star copolymers P(G-co-GEGE-g-EO) with acid-labile polyether core and PEG side chains was synthesized by using the P(G-co-GEGE) copolymers as multifunctional macroinitiators for AROP of EO. The new materials have been characterized in a detailed manner, revealing narrow to moderate molecular weight distributions. The degradation of these polymers under acidic conditions was characterized via SEC and ¹H NMR spectroscopy.