Poly(2-Oxazoline) Amphiphilicity Tunes the Excited-State Proton Transfer of Pyrenol-Based Polyphotoacids

The ability of light to change the properties of light-responsive polymers opens avenues for targeted release of cargo with a high degree of spatial and temporal control. Recently, we established photoacid polymers as light-switchable macromolecular amphiphiles. In these systems, light-induced excited-state proton transfer (ESPT) causes changes in amphilicity. However, as the intermolecular process itself critically depends on the local environment of the photoacid unit within the polymer, the overall amphiphilicity directly influences ESPT. Thus, understanding the impact of the local environment on the photophysics of photoacidic side chains is key to material design. In this contribution we address both thermodynamic and kinetic aspects of ESPT in oxazoline-based amphiphilic polymers with pyrenol-based photoacid side chains. We will compare the effect of polymer design, i. e. statistical and block arrangements, i. e. in poly[(2-ethyl-2-oxazoline)-co-(1-(6/8-hydroxyperene)sulphonylaziridine)] and poly(2-ethyl-2-oxazoline)-block-poly[(2-ethyl-2-oxazoline)-co-(2-(3-(6-hydroxypyrene)sulphonamide)propyl-2-oxazoline), on the intermolecular proton transfer reaction by combining steady-state and time-resolved absorption and emission spectroscopy. ESPT appears more prominent in the statistical copolymer compared to a block copolymer with overall similar pyrenol loading. We hypothesize that the difference is due to different local chain arrangements adopted by the polymers in the two cases.

A Concise Review on Effect of PEGylation on the Properties of Lipid-Based Nanoparticles

Nanoparticle-based drug delivery systems have emerged as promising platforms for enhancing therapeutic efficacy while minimizing off-target effects. Among various strategies employed to optimize these systems, polyethylene glycol (PEG) modification, known as PEGylation-the covalent attachment of PEG to nanoparticles, has gained considerable attention for its ability to impart stealth properties to nanoparticles while also extending circulation time and improving biocompatibility. PEGylation extends to different drug delivery systems, in specific, nanoparticles for targeting cancer cells, where the concentration of drug in the cancer cells is improved by virtue of PEGylation. The primary challenge linked to PEGylation lies in its confirmation. Numerous research findings provide comprehensive insights into selecting PEG for various PEGylation methods. In this review, we have endeavored to consolidate the outcomes concerning the choice of PEG and diverse PEGylation techniques.

Striving for Uniformity: A Review on Advances and Challenges To Achieve Uniform Polyethylene Glycol

Poly(ethylene glycol) (PEG) is the polymer of choice in drug delivery systems due to its biocompatibility and hydrophilicity. For over 20 years, this polymer has been widely used in the drug delivery of small drugs, proteins, oligonucleotides, and liposomes, improving the stability and pharmacokinetics of many drugs. However, despite the extensive clinical experience with PEG, concerns have emerged related to its use. These include hypersensitivity, purity, and nonbiodegradability. Moreover, conventional PEG is a mixture of polymers that can complicate drug synthesis and purification leading to unwanted immunogenic reactions. Studies have shown that uniform PEGylated drugs may be more effective than conventional PEGylated drugs as they can overcome issues related to molecular heterogeneity and immunogenicity. This has led to significant research efforts to develop synthetic procedures to produce uniform PEGs (monodisperse PEGs). As a result, iterative step-by-step controlled synthesis methods have been created over time and have shown promising results. Nonetheless, these procedures have presented numerous challenges due to their iterative nature and the requirement for multiple purification steps, resulting in increased costs and time consumption. Despite these challenges, the synthetic procedures went through several improvements. This review summarizes and discusses recent advances in the synthesis of uniform PEGs and its derivatives with a focus on overall yields, scalability, and purity of the polymers. Additionally, the available characterization methods for assessing polymer monodispersity are discussed as well as uniform PEG applications, side effects, and possible alternative polymers that can overcome the drawbacks.

Solid-Phase Synthesis as a Tool to Create Exactly Defined, Branched Polymer Vectors for Cell Membrane Targeting

Modern drug formulations often require, besides the active drug molecule, auxiliaries to enhance their pharmacological properties. Tailor-made, biocompatible polymers covalently connected to the drug molecule can fulfill this function by increasing its solubility, reducing its toxicity, and guiding it to a specific target. If targeting membrane-bound proteins, localization of the drug close to the cell membrane and its target is beneficial to increase drug efficiency and residence time. In this study, we present the synthesis of highly defined, branched polymeric structures with membrane-binding properties. One to three hydrophilic poly(ethylene oxide) or poly(2-ethyloxazoline) side chains were connected via a peptoid backbone using a two-step iterative protocol for solid-phase peptoid synthesis. Additional groups, e.g., a hydrophobic anchor for membrane attachment, were introduced. Due to the nature of solid-phase synthesis, the number and order of the side chains and additional units can be precisely defined. The method proved to be versatile for the generation of multifunctional, branched polymeric structures of molecular weights up to approximately 7000 g mol-1. The behavior of all compounds towards biological membranes and cells was investigated using liposomes as cell membrane models, HEK293 and U251-MG cell lines, and red blood cells, thereby demonstrating their potential value as drug auxiliaries with cell membrane affinity.

Exploring the Potential of Nanogels: From Drug Carriers to Radiopharmaceutical Agents

Nanogels open up access to a wide range of applications and offer among others hopeful approaches for use in the field of biomedicine. This review provides a brief overview of current developments of nanogels in general, particularly in the fields of drug delivery, therapeutic applications, tissue engineering, and sensor systems. Specifically, cyclodextrin (CD)-based nanogels are important because they have exceptional complexation properties and are highly biocompatible. Nanogels as a whole and CD-based nanogels in particular can be customized in a wide range of sizes and equipped with a desired surface charge as well as containing additional molecules inside and outside, such as dyes, solubility-mediating groups or even biological vector molecules for pharmaceutical targeting. Currently, biological investigations are mainly carried out in vitro, but more and more in vivo applications are gaining importance. Modern molecular imaging methods are increasingly being used for the latter. Due to an extremely high sensitivity and the possibility of obtaining quantitative data on pharmacokinetic and pharmacodynamic properties, nuclear methods such as single photon emission computed tomography (SPECT) and positron emission tomography (PET) using radiolabeled compounds are particularly suitable here. The use of radiolabeled nanogels for imaging, but also for therapy, is being discussed.

Mechanism of Action of Oxazoline-Based Antimicrobial Polymers Against Staphylococcus aureus: In Vivo Antimicrobial Activity Evaluation

Antimicrobial-resistant pathogens have reached alarming levels, becoming one of the most pressing global health issues. Hence, new treatments are necessary for the fight against antimicrobial resistance. Synthetic nanoengineered antimicrobial polymers (SNAPs) have emerged as a promising alternative to antimicrobial peptides, overcoming some of their limitations while keeping their key features. Herein, a library of amphiphilic oxazoline-based SNAPs using cationic ring-opening polymerization (CROP) is designed. Amphipathic compounds with 70% cationic content exhibit the highest activity against clinically relevant Staphylococcus aureus isolates, maintaining good biocompatibility in vitro and in vivo. The mechanism of action of the lead compounds against S. aureus is assessed using various microscopy techniques, indicating cell membrane disruption, while the cell wall remains unaffected. Furthermore, a potential interaction of the compounds with bacterial DNA is shown, with possible implications on bacterial division. Finally, one of the compounds exhibits high efficacy in vivo in an insect infection model.

Poly(2-oxazoline)-Based Polyplexes as a PEG-Free Plasmid DNA Delivery Platform

The present study expands the versatility of cationic poly(2-oxazoline) (POx) copolymers as a polyethylene glycol (PEG)-free platform for gene delivery to immune cells, such as monocytes and macrophages. Several block copolymers are developed by varying nonionic hydrophilic blocks (poly(2-methyl-2-oxazoline) (pMeOx) or poly(2-ethyl-2-oxazoline) (pEtOx), cationic blocks, and an optional hydrophobic block (poly(2-isopropyl-2-oxazoline) (iPrOx). The cationic blocks are produced by side chain modification of 2-methoxy-carboxyethyl-2-oxazoline (MestOx) block precursor with diethylenetriamine (DET) or tris(2-aminoethyl)amine (TREN). For the attachment of a targeting ligand, mannose, azide-alkyne cycloaddition click chemistry methods are employed. Of the two cationic side chains, polyplexes made with DET-containing copolymers transfect macrophages significantly better than those made with TREN-based copolymer. Likewise, nontargeted pEtOx-based diblock copolymer is more active in cell transfection than pMeOx-based copolymer. The triblock copolymer with hydrophobic block iPrOx performs poorly compared to the diblock copolymer which lacks this additional block. Surprisingly, attachment of a mannose ligand to either copolymer is inhibitory for transfection. Despite similarities in size and design, mannosylated polyplexes result in lower cell internalization compared to nonmannosylated polyplexes. Thus, PEG-free, nontargeted DET-, and pEtOx-based diblock copolymer outperforms other studied structures in the transfection of macrophages and displays transfection levels comparable to GeneJuice, a commercial nonlipid transfection reagent.

Hydrolysis of hydrophobic poly(2-oxazoline)s and their subsequent modification via aza-Michael addition

Partially hydrolysed poly(2-oxazoline)s possess unique properties. However, much of the focus in this area has been on water soluble poly(2-oxazoline)s. Where hydrophobic poly(2-oxazoline)s have been used, this is often for selective hydrolysis. However, hydrolysis of very hydrophobic polymers could lead to interesting solution behaviour. Herein, we describe universal conditions for the hydrolysis of poly(2-alkyl-2-oxazoline)s suitable for both hydrophobic and hydrophilic 2-oxazolines. We show that the system utilised gives comparable rates to that of water alone for poly(2-ethyl-2-oxazoline). In addition, poly(2-fatty acid-2-oxazoline) was hydrolysed using the developed system and was found to proceed in a controlled manner allowing the targeting of specific degrees of hydrolysis, albeit much slower than for poly(2-ethyl-2-oxazoline). Finally, we demonstrate the partial functionalisation of poly(2-oxazoline)-poly(ethylene imine) co-polymers via aza-Michael addition.

Hydrogelation from Self-Assembled and Scaled-Down Chitin Nanofibers by the Modification of Highly Polar Substituents

Chitin nanofibers (ChNFs) with a bundle structure were fabricated via regenerative self-assembly at the nanoscale from a chitin ion gel with an ionic liquid using methanol. Furthermore, the bundles were disentangled by partial deacetylation under alkaline conditions, followed by cationization and electrostatic repulsion in aqueous acetic acid to obtain thinner nanofibers called scaled-down ChNFs. This review presents a method for hydrogelation from self-assembled and scaled-down ChNFs by modifying the highly polar substituents on ChNFs. The modification was carried out by the reaction of amino groups on ChNFs, which were generated by partial deacetylation, with reactive substituent candidates such as poly(2-oxazoline)s with electrophilic living propagating ends and mono- and oligosaccharides with hemiacetallic reducing ends. The substituents contributed to the formation of network structures from ChNFs in highly polar dispersed media, such as water, to produce hydrogels. Moreover, after the modification of the maltooligosaccharide primers on ChNFs, glucan phosphorylase-catalyzed enzymatic polymerization was performed from the primer chain ends to elongate the amylosic graft chains on ChNFs. The amylosic graft chains formed double helices between ChNFs, which acted as physical crosslinking points to construct network structures, giving rise to hydrogels.

Preparation of Triptolide Nano Drug Delivery System and Its Antitumor Activity In-Vitro

Triptolide (as an effective antitumor drug) is limited in clinical application because of its poor solubility and absorption in-vivo. Herein, we prepared folic acid modified polymer micelles to encapsulate triptolide and enhance its biologicalavailability coupled with antitumor effect. We prepared nano-micelles of triptolide through thin lipid film hydrational method. Physical properties and in vitro release characterization of Fol-Plla-cl-Peg-Plla-cl-Tmicelles were evaluated, while bioavailability of the formulation in rats was investigated. Tumor targeting potential of micelles was determined by observing the uptake of A549 cells. In-Vitro antitumor activity of micelles and free triptolide (API) was investigated with MTT assay. The prepared polymer material exhibited no cytotoxicity. The particle size distribution of Fol-Plla-cl-Peg-Plla-cl-T micelles was uniform and small, with good stability and high efficiency of entrapment. Triptolide In-Vitro release from micelles demonstrated slow and continuous released for 24 h. Compared with API, the half-life of micelles was prolonged, whilst its bioavailability in-vivo was increased by about 6.35 times. More importantly, Fol-Plla-cl-Peg-Plla-cl-T micelles significantly improved the antitumor activity of triptolide and showed good tumor targeting potential. Fol-Plla-cl-Peg-Plla-cl-T micelles could improve the bioavailability and antitumor activity of triptolide, amid demonstration of good tumor targeting and high safety.

Stable amorphous solid dispersion of flubendazole with high loading via electrospinning

In this work, an important step is taken towards the bioavailability improvement of poorly water-soluble drugs, such as flubendazole (Flu), posing a challenge in the current development of many novel oral-administrable therapeutics. Solvent electrospinning of a solution of the drug and poly (2-ethyl-2-oxazoline) (PEtOx) is demonstrated to be a viable strategy to produce stable nanofibrous amorphous solid dispersions (ASDs) with ultrahigh drug-loadings (up to 55 wt% Flu) and long-term stability (at least one year). Importantly, at such high drug loadings, the concentration of the polymer in the electrospinning solution has to be lowered below the concentration where it can be spun in absence of the drug as the interactions between the polymer and the drug result in increased solution viscosity. A combination of experimental analysis and molecular dynamics simulations revealed that this formulation strategy provides strong, dominant and highly stable hydrogen bonds between the polymer and the drug, which is crucial to obtain the high drug-loadings and to preserve the long-term amorphous character of the ASDs upon storage. In vitro drug release studies confirm the remarkable potential of this electrospinning formulation strategy by significantly increased drug solubility values and dissolution rates (respectively tripled and quadrupled compared to the crystalline drug), even after storing the formulation for one year.

Quaternized Sodium Alginate-g-Ethyl-Oxazoline Copolymer Brushes and Their Supramolecular Networks via Hydrogen Bonding

Novel copolymer brushes of quaternized sodium alginate-g-(2-ethyl-2-oxazoline)_n are achieved by the grafting reaction of 2-ethyl-2-oxazoline (EOX) from benzyl bromide groups in quaternized sodium alginate (QSA). The average number of (EOX)_n structural units is mediated from 1 to 5 by changing the molar ratio of the EOX monomer to benzyl bromide side groups. There exists obvious microphase separation between the QSA backbone and (EOX)_n segments in the copolymer brushes due to their thermodynamic incompatibility. The strong hydrogen-bonding interaction between -OH groups in the backbone and N─C═O groups in (EOX)_n segments is helpful for the construction of reversible supramolecular networks. The copolymer brushes show low cytotoxicity for HeLa cells and good antibacterial properties for Escherichia coli and Staphylococcus aureus for the contribution of hydrophilic (EOX)_n segments and antibacterial activity of the quaternary ammonium. The antiprotein behavior of polymer surfaces is improved after rearrangement of (EOX)_n segments by tetrahydrofuran (THF) vapor induction. These copolymer brushes have good prospects for biomedical applications.

Eco-Friendly Synthesis of PEtOz-PA: A Promising Polymer for the Formulation of Curcumin-Loaded Micelles

The need to develop alternative methods or to use "green" solvents constitutes an essential strategy under the emerging field of green chemistry, particularly in the development of new synthetic strategies in the field of pharmaceutic industry. We report an eco-friendly method of synthesis of poly(2-ethyl-2-oxazoline)-palmitoylate (PEtOz-PA) using Er(OTf)₃ as Lewis's acid catalyst in 2-MeTHF. The novel biomolecule derivative was characterized to confirm palmitoyl group substitution and employed for the formulation, characterization, and antioxidant activity evaluation of curcumin-loaded polymeric micelles.

Nucleobase-crosslinked poly(2-oxazoline) nanoparticles as paclitaxel carriers with enhanced stability and ultra-high drug loading capacity for breast cancer therapy

Poly(2-oxazoline) (POx) has been regarded as a potential candidate for drug delivery carrier to meet the challenges of nanomedicine clinical translation, due to its excellent biocompatibility and self-assembly properties. The drug loading capacity and stability of amphiphilic POxs as drug nanocarriers, however, tend to be insufficient. Herein, we report a strategy to prepare nucleobase-crosslinked POx nanoparticles (NPs) with enhanced stability and ultra-high paclitaxel (PTX) loading capacity for breast cancer therapy. An amphiphilic amine-functionalized POx (PMBEOx-NH₂) was firstly prepared through a click reaction between cysteamines and vinyl groups in poly(2-methyl-2-oxazoline)-block-poly (2‑butyl‑2-oxazoline-co-2-butenyl-2-oxazoline) (PMBEOx). Complementary nucleobase-pairs adenine (A) and uracil (U) were subsequently conjugated to PMBEOx-NH₂ to give functional POxs (POxA and POxU), respectively. Due to the nucleobase interactions formed between A and U, NPs formed by POxA and POxU at a molar ratio of 1:1 displayed ultrahigh PTX loading capacity (38.2%, PTX/POxA@U), excellent stability, and reduced particle size compared to the uncross-linked PTX-loaded NPs (PTX/PMBEOx). Besides the prolonged blood circulation and enhanced tumor accumulation, the smaller PTX/POxA@U NPs also have better tumor penetration ability compared with PTX/PMBEOx, thus leading to a higher tumor suppression rate in two murine breast cancer models (E0711 and 4T1). These results proved that the therapeutic effect of chemotherapeutic drugs could be improved remarkably through a reasonable optimization of nanocarriers.

Bone-Adhesive Hydrogels Based on Dual Crosslinked Poly(2-oxazoline)s

The development of bone glues based on bone-adhesive hydrogels to allow for facile bone fracture fixation remains a major challenge. Herein, dual crosslinked hydrogels that combine tunable stiffness, ductility, and self-healing capacity are successfully synthesized. The resulting double network hydrogel is formed by chemical crosslinking of N-hydroxysuccinimide-functionalized poly(2-oxazoline)s(POx-NHS)"?> with amine-functionalized poly(2-oxazoline)s, and physical crosslinking of alendronate-functionalized poly(2-oxazoline)s (POx-Ale) with calcium ions in solution. The use of an excess of alendronate-functionalized POx-Ale polymers also ensures affinity toward calcium cations in the mineral phase of bone, thereby rendering these hydrogels adhesive to bone. The mechanical and bone-adhesive properties of these novel hydrogels are superior to commercially available fibrin sealants. Moreover, hydrogels retain their bone-adhesive properties under wet conditions. Although the dual crosslinked hydrogels swell considerably, they are stable upon immersion in phosphate-buffered saline (up to 12 d) and even in ethylenediaminetetraacetic acid solution. The enhanced mechanical and bone-adhesive properties of these hydrogels, as well as their in vitro stability, indicate that they have much application potential as bone-adhesive glues.

Development of polymer-based nanoparticles for zileuton delivery to the lung: PMeOx and PMeOzi surface chemistry reduces interactions with mucins

In this paper, two amphiphilic graft copolymers were synthesized by grafting polylactic acid (PLA) as hydrophobic chain and poly(2-methyl-2-oxazoline) (PMeOx) or poly(2-methyl-2-oxazine) (PMeOzi) as hydrophilic chain, respectively, to a backbone of α,β-poly(N-2-hydroxyethyl)-D,L-aspartamide (PHEA). These original graft copolymers were used to prepare nanoparticles delivering Zileuton in inhalation therapy. Among various tested methods, direct nanoprecipitation proved to be the best technique to prepare nanoparticles with the smallest dimensions, the narrowest dimensional distribution and a spherical shape. To overcome the size limitations for administration by inhalation, the nano-into-micro strategy was applied, encapsulating the nanoparticles in water-soluble mannitol-based microparticles by spray-drying. This process has allowed to produce spherical microparticles with the proper size for optimal lung deposition, and, once in contact with fluids mimicking the lung district, able to dissolve and release non-aggregated nanoparticles, potentially able to spread through the mucus, releasing about 70% of the drug payload in 24 h.

Tuning the Thermogelation and Rheology of Poly(2-Oxazoline)/Poly(2-Oxazine)s Based Thermosensitive Hydrogels for 3D Bioprinting

As one kind of "smart" material, thermogelling polymers find applications in biofabrication, drug delivery and regenerative medicine. In this work, we report a thermosensitive poly(2-oxazoline)/poly(2-oxazine) based diblock copolymer comprising thermosensitive/moderately hydrophobic poly(2-N-propyl-2-oxazine) (pPrOzi) and thermosensitive/moderately hydrophilic poly(2-ethyl-2-oxazoline) (pEtOx). Hydrogels were only formed when block length exceeded certain length (≈100 repeat units). The tube inversion and rheological tests showed that the material has then a reversible sol-gel transition above 25 wt.% concentration. Rheological tests further revealed a gel strength around 3 kPa, high shear thinning property and rapid shear recovery after stress, which are highly desirable properties for extrusion based three-dimensional (3D) (bio) printing. Attributed to the rheology profile, well resolved printability and high stackability (with added laponite) was also possible. (Cryo) scanning electron microscopy exhibited a highly porous, interconnected, 3D network. The sol-state at lower temperatures (in ice bath) facilitated the homogeneous distribution of (fluorescently labelled) human adipose derived stem cells (hADSCs) in the hydrogel matrix. Post-printing live/dead assays revealed that the hADSCs encapsulated within the hydrogel remained viable (≈97%). This thermoreversible and (bio) printable hydrogel demonstrated promising properties for use in tissue engineering applications.

Poly(tertiary amide acrylate) Copolymers Inspired by Poly(2-oxazoline)s: Their Blood Compatibility and Hydration States

Modifying the side chain of poly(meth)acrylate with moieties originating from biocompatible polymers can be an effective method for developing novel blood-compatible polymers. Inspired by biocompatible poly(2-methyl-2-oxazoline) (PMeOx) and poly(2-ethyl-2-oxazoline) (PEtOx), four water-soluble poly(tertiary amide acylate) analogues bearing a pendant tertiary amide were synthesized. The results of hemolysis and cell viability tests showed that all the poly(tertiary amide acylate) analogues were compatible with red blood cells, HeLa cells, and normal human dermal fibroblasts as PMeOx or PEtOx. Among the four poly(tertiary amide acylate) analogues, poly[2-(N-methylpropionamido)ethyl acrylate] (PPEA) and poly[2-(N-ethylacetamido)ethyl acrylate] (PEAE) showed thermosensitivity in aqueous solution; especially, PPEA (10 mg mL^-1) exhibited a lower critical solution temperature of 37 °C. Water-insoluble copolymers were prepared to investigate the possibility of applying these synthesized polymers as blood-compatible coatings. The poly[n-butyl methacrylate₇₀-co-2-(N-methylacetamido)ethyl methacrylate₃₀] (coPAEM) coatings significantly suppressed plasma protein adsorption, denaturation degree of adsorbed fibrinogen, and platelet adhesion. Intermediate water (IW), whose content can generally indicate the blood compatibility of polymers, was found in all hydrated homopolymers and copolymers by differential scanning calorimetry. The present work demonstrated that the tertiary amide moiety in the side chain of poly(meth)acrylate was an effective contributor to blood compatibility and IW.

Understanding the temperature induced aggregation of silica nanoparticles decorated with temperature-responsive polymers: Can a small step in the chemical structure make a giant leap for a phase transition?

Temperature-responsive nanomaterials have gained increasing interest over the past decade due their ability to undergo conformational changes in situ, in response to a change in temperature. One class of temperature-responsive polymers are those with lower critical solution temperature, which phase separate in aqueous solution above a critical temperature. When these temperature-responsive polymers are grafted to a solid nanoparticle, a change in their surface properties occurs above this critical temperature, from hydrophilic to more hydrophobic, giving them a propensity to aggregate. This study explores the temperature induced aggregation of silica nanoparticles functionalised with two isomeric temperature-responsive polymers with lower critical solution temperature (LCST) behavior, namely poly(N-isopropyl acrylamide) (PNIPAM), and poly(2-n-propyl-2-oxazoline) (PNPOZ) with similar molecular weights (5000 Da) and grafting density. These nanoparticles exhibited striking differences in the temperature of aggregation, which is consistent with LCST of each polymer. Using a combination of small-angle neutron scattering (SANS) and dynamic light scattering (DLS), we probed subtle differences in the aggregation mechanism for PNIPAM- and PNPOZ-decorated silica nanoparticles. The nanoparticles decorated with PNIPAM and PNPOZ show similar aggregation mechanism that was independent of polymer structure, whereby aggregation starts by the formation of small aggregates. A further increase in temperature leads to interaction between these aggregates and results in full-scale aggregation and subsequent phase separation.

Preparation and gelation behaviors of poly(2-oxazoline)-grafted chitin nanofibers

Based on our previous work on successful gelation of poly(2-methyl-2-oxazoline)-grafted chitin nanofibers (ChNFs) with high polar media, in this study, we investigated the preparation and gelation behaviors of the ChNFs having different poly(2-alkyl-2-oxazoline) graft chains, that is, poly(2-methyl-2-oxazoline), poly(2-isopropyl-2-oxazoline), and poly(2-butyl-2-oxazoline), with various disperse media. The grafting was carried out by reactions of living propagating ends of poly(2-alkyl-2-oxazoline)s with amino groups present on the self-assembled ChNFs, which were obtained from a chitin ion gel. The products formed gels in the reaction mixtures, which could be converted into hydrogels. All the products with the three poly(2-alkyl-2-oxazoline) graft chains formed gels with high polar media. Besides, gelation of the product with poly(2-butyl-2-oxazoline) was observed by immersing it in relatively non-polar media such as benzyl alcohol, ethyl acetate, and toluene. The formation process of network structures by the grafting of poly(2-alkyl-2-oxazoline)s on ChNFs is proposed to induce gelation of the products.

Antifouling Strategies for Electrochemical Biosensing: Mechanisms and Performance toward Point of Care Based Diagnostic Applications

Although there exist numerous established laboratory-based technologies for sample diagnostics and analyte detection, many medical and forensic science applications require point of care based platforms for rapid on-the-spot sample analysis. Electrochemical biosensors provide a promising avenue for such applications due to the portability and functional simplicity of the technology. However, the ability to develop such platforms with the high sensitivity and selectivity required for analysis of low analyte concentrations in complex biological samples remains a paramount issue in the field of biosensing. Nonspecific adsorption, or fouling, at the electrode interface via the innumerable biomolecules present in these sample types (i.e., serum, urine, blood/plasma, and saliva) can drastically obstruct electrochemical performance, increasing background "noise" and diminishing both the electrochemical signal magnitude and specificity of the biosensor. Consequently, this review aims to discuss strategies and concepts used throughout the literature to prevent electrode surface fouling in biosensors and to communicate the nature of the antifouling mechanisms by which they operate. Evaluation of each antifouling strategy is focused primarily on the fabrication method, experimental technique, sample composition, and electrochemical performance of each technology highlighting the overall feasibility of the platform for point of care based diagnostic/detection applications.

The role of poly(2-alkyl-2-oxazoline)s in hydrogels and biofabrication

Poly(2-alkyl-2-oxazoline)s (PAOXAs) have been rapidly emerging as starting materials in the design of tissue engineering supports and for the generation of platforms for cell cultures, especially in the form of hydrogels. Thanks to their biocompatibility, chemical versatility and robustness, PAOXAs now represent a valid alternative to poly(ethylene glycol)s (PEGs) and their derivatives in these applications, and in the formulation of bioinks for three-dimensional (3D) bioprinting. In this review, we summarize the recent literature where PAOXAs have been used as main components for hydrogels and biofabrication mixtures, especially highlighting how their easily tunable composition could be exploited to fabricate multifunctional biomaterials with an extremely broad spectrum of properties.

Stealth nanorods via the aqueous living crystallisation-driven self-assembly of poly(2-oxazoline)s

The morphology of nanomaterials critically influences their biological interactions. However, there is currently a lack of robust methods for preparing non-spherical particles from biocompatible materials. Here, we combine 'living' crystallisation-driven self-assembly (CDSA), a seeded growth method that enables the preparation of rod-like polymer nanoparticles, with poly(2-oxazoline)s (POx), a polymer class that exhibits 'stealth' behaviour and excellent biocompatibility. For the first time, the 'living' CDSA process was carried out in pure water, resulting in POx nanorods with lengths ranging from ∼60 to 635 nm. In vitro and in vivo study revealed low immune cell association and encouraging blood circulation times, but little difference in the behaviour of POx nanorods of different length. The stealth behaviour observed highlights the promising potential of POx nanorods as a next generation stealth drug delivery platform.

Cell-Mediated Immunoreactivity of Poly(2-isopropenyl-2-oxazoline) as Promising Formulation for Immunomodulation

Poly(2-isopropenyl-2-oxazoline) (PIPOx) represents a functional polymer with high potential for drug delivery, tissue engineering, and immunomodulation. The immunomodulatory efficiency of the PIPOx formulation has been studied in vitro following splenic cells and RAW 264.7 macrophages exposition. The cell-specific immunomodulative effect on production of Th1, Th2, Th17, and Treg signature cytokines has been demonstrated. The impact on the functionality of PIPOx-sensitized RAW 264.7 macrophages was assessed by cell phagocytosis. Time- and concentration-dependent cell internalization and intracellular organelles colocalization of fluorescently labeled PIPOx has been examined. The in vitro results demonstrated the PIPOx bioavailability and the capability of triggering immune cell responses resulting in the induced production of cell-specific signature interleukins, important prerequisite properties for future potential biomedical applications.

Copolymer chain formation of 2-oxazolines by in situ 1H-NMR spectroscopy: dependence of sequential composition on substituent structure and monomer ratios

In situ 1H NMR characterization of copolymerization reactions of various 2-oxazoline monomers at different molar ratios offers detailed insight into the build-up and composition of the polymer chains. Various 2-oxazolines were copolymerized in one single solvent, butyronitrile, with 2-dec-9'-enyl-2-oxazoline, where the double bond allows for post-polymerization modification and can function as a crosslinking unit to form polymer networks. The types of the monomers and their molar ratios in the feed have a strong effect on the microstructure of the forming copolymer chains. Copolymers comprising 2-dec-9'-enyl-2-oxazoline and either 2-ethyl-, 2-isopropyl-, 2-butyl-, 2-heptyl, 2-nonyl- or 2-phenyl-2-oxazoline, show significant differences in sequential structure of copolymers ranging from block to gradient and random ordering of the monomer units. 1H NMR was found to be a powerful tool to uncover detailed oxazoline copolymerization kinetics and evolution of chain composition.