Thermoresponsive poly(oligo ethylene glycol acrylates)

Dual responsive nanogels for intracellular doxorubicin delivery

Nanosized polymeric delivery systems that encapsulate drug molecules and release them in response to a specific intracellular stimulus are of promising interest for cancer therapy. Here, we demonstrated a simple and fast synthetic protocol of redox-responsive nanogels with high drug encapsulation efficiency and stability. The prepared nanogels displayed narrow size distributions and versatility of surface modification. The polymer precursor of these nanogels is based on a random copolymer that contains oligoethyleneglycol (OEG) and pyridyldisulfide (PDS) units as side-chain functionalities. The nanogels were prepared through a lock-in strategy in aqueous media via self cross-linking of PDS groups. By changing polymer concentration, we could control the size of nanogels in range of 80-115nm. The formed nanogels presented high doxorubicin (DOX) encapsulation efficiency (70% (w/w)) and displayed pH and redox-controlled drug release triggered by conditions mimicking the reducible intracellular environment. The nanogels displayed an excellent cytocompatibility and were effectively endocytosed by A2780CP ovarian cancer cells, which make them promising nanomaterials for the efficient intracellular delivery of anticancer drugs.

Exploration of Doubly Thermal Phase Transition Process of PDEGA-b-PDMA-b-PVCL in Water

Understanding of phase transition mechanism of thermoresponsive polymers is the basis for the rational design of smart materials with predictable properties. Linear ABC triblock terpolymer poly(di(ethylene glycol)ethyl ether acrylate)-b-poly(N,N-dimethylacrylamide)-b-poly(N-vinylcaprolactam) (PDEGA-b-PDMA-b-PVCL) was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. The doubly thermal phase transition of PDEGA-b-PDMA-b-PVCL in aqueous solution was investigated by a combination of nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), turbidimetry, and dynamic light scattering (DLS). The terpolymer self-assembles into micelles with PDEGA being the core-forming block during the first lower critical solution temperature (LCST) transition corresponding to PDEGA, which is followed by a second LCST transition corresponding to PVCL, resulting in the formation of micellar aggregates. The PDMA middle segment plays an important role as an isolation zone to prevent cooperative dehydration of the PDEGA and PVCL segments, and therefore, two independent LCST transitions corresponding to PDEGA and PVCL were observed. Furthermore, FT-IR with perturbation correlation moving window (PCMW) and two-dimensional spectroscopy (2DCOS) was applied to elucidate the two-step phase transition mechanism of this terpolymer. It was observed that the CH, ester carbonyl, and ether groups of PDEGA change prior to the CH and amide carbonyl groups of PVCL, further supporting that the two phase transitions corresponding to PDEGA and PVCL indeed occur without mutual interferences.

Thermoresponsive Polymers and Inverse Opal Hydrogels for the Detection of Diols

Responsive inverse opal hydrogels functionalized by boroxole moieties were synthesized and explored as sensor platforms for various low molar mass as well as polymeric diols and polyols, including saccharides, glycopolymers and catechols, by exploiting the diol induced modulation of their structural color. The underlying thermoresponsive water-soluble copolymers and hydrogels exhibit a coil-to-globule or volume phase transition, respectively, of the LCST-type. They were prepared from oligoethylene oxide methacrylate (macro)monomers and functionalized via copolymerization to bear benzoboroxole moieties. The resulting copolymers represent weak polyacids, which can bind specifically to diols within an appropriate pH window. Due to the resulting modulation of the overall hydrophilicity of the systems and the consequent shift of their phase transition temperature, the usefulness of such systems for indicating the presence of catechols, saccharides, and glycopolymers was studied, exploiting the diol/polyol induced shifts of the soluble polymers' cloud point, or the induced changes of the hydrogels' swelling. In particular, the increased acidity of benzoboroxoles compared to standard phenylboronic acids allowed performing the studies in PBS buffer (phosphate buffered saline) at the physiologically relevant pH of 7.4. The inverse opals constructed of these thermo- and analyte-responsive hydrogels enabled following the binding of specific diols by the induced shift of the optical stop band. Their highly porous structure enabled the facile and specific optical detection of not only low molar mass but also of high molar mass diol/polyol analytes such as glycopolymers. Accordingly, such thermoresponsive inverse opal systems functionalized with recognition units represent attractive and promising platforms for the facile sensing of even rather big analytes by simple optical means, or even by the bare eye.

Role of Aromatic Interactions in Temperature-Sensitive Amphiphilic Supramolecular Assemblies

Aromatic interactions were found to greatly influence the temperature-dependent dynamic behavior within supramolecular assemblies. Using an amphiphilic dendron, we systematically changed the hydrophobic groups introducing increasing levels of aromaticity while keeping the hydrophilic part constant. We show that the supramolecular assemblies become less sensitive to temperature changes when aromatic interactions in the aggregate are increased. Conversely, the absence of aromaticity in the hydrophobic moieties produces temperature-sensitive aggregates. These results show that subtle molecular-level interactions can be utilized to control temperature-sensitive behavior in the nanoscale. These findings open up new design strategies to rationally tune the behavior of stimuli-responsive supramolecular assemblies on multiple spatiotemporal scales.

Understanding the thermosensitivity of POEGA-based star polymers: LCST-type transition in water vs. UCST-type transition in ethanol

The lower critical solution temperature (LCST) transition in water and the upper critical solution temperature (UCST) transition in ethanol of poly(oligo(ethylene glycol) acrylate) (POEGA)-based core cross-linked star (CCS) polymers have been investigated and compared by employing turbidity, dynamic light scattering (DLS), (1)H NMR and FTIR measurements. Macroscopic phase transitions in water and in ethanol were observed to occur when passing through the transition temperature, as revealed by DLS and turbidity measurements. Analysis by IR indicated that the interactions between the polymer chains and solvent molecules in water are stronger than those in ethanol such that the CCS polymer arm chains in water adopt more extended conformations. Moreover, hydrophobic interaction among the aliphatic groups plays a predominant role in the LCST-type transition in water whereas weak solvation of the polymer chains results in the UCST-type transition in ethanol. Additionally, the LCST-type transition in water was observed to be much more abrupt and complete than the UCST-type transition in ethanol, as suggested by (1)H NMR and IR at the molecular level. Finally, an abnormal "forced hydration" phenomenon was observed during the LCST transition upon heating. This study provides a detailed understanding of the subtle distinctions between the thermal transitions of CCS polymers in two commonly used solvents, which may be useful to guide future materials design for a wide range of applications.

Poly(Ionic Liquid) Semi-Interpenetrating Network Multi-Responsive Hydrogels

Herein we describe poly(ionic liquid) hydrogel actuators that are capable of responding to multiple stimuli, namely temperature, ionic strength and white light irradiation. Using two starting materials, a crosslinked poly ionic liquid (PIL) and a linear poly(N-isopropylacrylamide-co-spiropyran-co-acrylic acid), several semi-interpenetrating (sIPN) hydrogels were synthesised. The dimensions of hydrogels discs were measured before and after applying the stimuli, to quantify their response. Samples composed of 100% crosslinked PIL alone showed an average area reduction value of ~53% when the temperature was raised from 20 °C to 70 °C, ~24% when immersed in 1% w/w NaF salt solution and no observable photo-response. In comparison, sIPNs containing 300% w/w linear polymer showed an average area reduction of ~45% when the temperature was raised from 20 °C to 70 °C, ~36% when immersed in 1% NaF w/w salt solution and ~10% after 30 min exposure to white light irradiation, respectively. Moreover, by varying the content of the linear component, fine-control over the photo-, thermo- and salt response, swelling-deswelling rate and mechanical properties of the resulting sIPN was achieved.

Advancing biomaterials of human origin for tissue engineering

Biomaterials have played an increasingly prominent role in the success of biomedical devices and in the development of tissue engineering, which seeks to unlock the regenerative potential innate to human tissues/organs in a state of deterioration and to restore or reestablish normal bodily function. Advances in our understanding of regenerative biomaterials and their roles in new tissue formation can potentially open a new frontier in the fast-growing field of regenerative medicine. Taking inspiration from the role and multi-component construction of native extracellular matrices (ECMs) for cell accommodation, the synthetic biomaterials produced today routinely incorporate biologically active components to define an artificial in vivo milieu with complex and dynamic interactions that foster and regulate stem cells, similar to the events occurring in a natural cellular microenvironment. The range and degree of biomaterial sophistication have also dramatically increased as more knowledge has accumulated through materials science, matrix biology and tissue engineering. However, achieving clinical translation and commercial success requires regenerative biomaterials to be not only efficacious and safe but also cost-effective and convenient for use and production. Utilizing biomaterials of human origin as building blocks for therapeutic purposes has provided a facilitated approach that closely mimics the critical aspects of natural tissue with regard to its physical and chemical properties for the orchestration of wound healing and tissue regeneration. In addition to directly using tissue transfers and transplants for repair, new applications of human-derived biomaterials are now focusing on the use of naturally occurring biomacromolecules, decellularized ECM scaffolds and autologous preparations rich in growth factors/non-expanded stem cells to either target acceleration/magnification of the body's own repair capacity or use nature's paradigms to create new tissues for restoration. In particular, there is increasing interest in separating ECMs into simplified functional domains and/or biopolymeric assemblies so that these components/constituents can be discretely exploited and manipulated for the production of bioscaffolds and new biomimetic biomaterials. Here, following an overview of tissue auto-/allo-transplantation, we discuss the recent trends and advances as well as the challenges and future directions in the evolution and application of human-derived biomaterials for reconstructive surgery and tissue engineering. In particular, we focus on an exploration of the structural, mechanical, biochemical and biological information present in native human tissue for bioengineering applications and to provide inspiration for the design of future biomaterials.

Low concentration thermoresponsive hydrogels from readily accessible triblock copolymers

Dilute (<1 wt%) aqueous solutions of ultrahigh molecular weight triblock copolymers (with M_n up to 500 000 g mol⁻¹) comprising a long central hydrophilic block of polydimethylacrylamide and shorter terminal blocks of poly(N-isopropylacrylamide) form gels on heating.

On the abnormal “forced hydration” behavior of P(MEA-co-OEGA) aqueous solutions during phase transition from infrared spectroscopic insights

During the phase separation of POEGA in water, C–H groups exhibit dehydration, whereas CO and C–O–C groups present “forced hydration”.

Facile production of nanoaggregates with tuneable morphologies from thermoresponsive P(DEGMA-co-HPMA)

RAFT-mediated emulsion polymerization of styrene and subsequent morphological transition produces nanoaggregates with tuneable morphologies.

N-Ester-substituted polyacrylamides with a tunable lower critical solution temperature (LCST): the N-ester-substitute dependent thermoresponse

New thermoresponsive polymers ofN-ester-substituted polyacrylamides were discovered, and theN-ester-substitute exerting a great influence on the solution property was demonstrated.

Triply responsive soft matter nanoparticles based on poly[oligo(ethylene glycol) methyl ether methacrylate-block-3-phenylpropyl methacrylate] copolymers

The stimulus-responsive properties of nanoparticles based on poly[oligo(ethylene glycol) methyl ether methacrylate-b-3-phenylpropyl methacrylate] (p(OEGMA-b-PPMA)) copolymers in alcohols are described.

Exploring the influence of the poly(4-vinyl pyridine) segment on the solution properties and thermal phase behaviours of oligo(ethylene glycol) methacrylate-based block copolymers: the different aggregation processes with various morphologies

P(MEO₂MA-co-OEGMA)-b-P4VP copolymers with different lengths of P4VP segments exhibit diverse aggregation processes with various morphologies upon heating.

Poly(3-imidazolyl-2-hydroxypropyl methacrylate) – a new polymer with a tunable upper critical solution temperature in water

A novel imidazole-bearing polymer is synthesized and its solubility in water increases as the solution temperature rises or pH increases.

Stimuli-responsive poly(N-vinylcaprolactam-co-2-methoxyethyl acrylate) core–shell microgels: facile synthesis, modulation of surface properties and controlled internalisation into cells

Poly(N-vinylcaprolactam-co-2-methoxyethyl acrylate) core–shell microgels as imaging/diagnostic system.

Synthesis and Postpolymerization Modification of Thermoresponsive Coatings Based on Pentaerythritol Monomethacrylate: Surface Analysis, Wettability, and Protein Adsorption

Properties of novel temperature-responsive hydroxyl-containing poly(pentaerythritol monomethacrylate) (PPM) coatings, polymerized from oligoperoxide grafted to glass surface premodified with (3-aminopropyl)triethoxysilane, are presented. Molecular composition, chemical state, thickness, and wettability are examined with time of flight-secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), ellipsometry, and contact angle measurements, respectively. Temperature-induced changes in hydrophobicity of grafted PPM brushes are revealed by water contact angle and ellipsometric measurements. Partial postpolymerization modification of hydroxyl groups (maximum a few percent), performed with acetyl chloride or pyromellitic acid chloride, is demonstrated to preserve thermal response of coatings. Adsorption of bovine serum albumin to PPM brushes, observed with fluorescence microscopy, is higher than on glass in contrast to similar hydroxyl-containing layers reported as nonfouling. Enhanced and temperature-controlled protein adsorption is obtained after postpolymerization modification with pyromellitic acid chloride.

Influence of backbone conformational rigidity in temperature-sensitive amphiphilic supramolecular assemblies

Molecular design features that endow amphiphilic supramolecular assemblies with a unique temperature-sensitive transition have been investigated. We find that conformational rigidity in the backbone is an important feature for eliciting this feature. We also find that intramolecular hydrogen-bonding can induce such rigidity in amphiphile backbone. Guest encapsulation stability of these assemblies was found to be significantly altered within a narrow temperature window, which correlates with the temperature-sensitive size transition of the molecular assembly. Molecular design principles demonstrated here could have broad implications in developing future temperature-responsive systems.

Responsive inverse opal hydrogels for the sensing of macromolecules

Dual responsive inverse opal hydrogels were designed as autonomous sensor systems for (bio)macromolecules, exploiting the analyte-induced modulation of the opal's structural color. The systems that are based on oligo(ethylene glycol) macromonomers additionally incorporate comonomers with various recognition units. They combine a coil-to-globule collapse transition of the LCST type with sensitivity of the transition temperature toward molecular recognition processes. This enables the specific detection of macromolecular analytes, such as glycopolymers and proteins, by simple optical methods. While the inverse opal structure assists the effective diffusion even of large analytes into the photonic crystal, the stimulus responsiveness gives rise to strong shifts of the optical Bragg peak of more than 100 nm upon analyte binding at a given temperature. The systems' design provides a versatile platform for the development of easy-to-use, fast, and low-cost sensors for pathogens.