Poly(N-isopropylacrylamide) modified polydopamine as a temperature-responsive surface for cultivation and harvest of mesenchymal stem cells

Fabrication of a novel magnetic carbon nanotube coated with polydopamine modified with EDTA for removing Cd2+ and Pb2+ ions from an aqueous solution

This work demonstrates the preparation of a new, effective, and reusable magnetic adsorbent by functionalizing dopamine with ethylenediaminetetraacetic dianhydride and polymerizing it on the surface of magnetic carbon nanotubes (EDTA@PD-CNT/Fe3O4). The adsorbent was analyzed using XRD, FT-IR, Zeta potential, FE-SEM, EDX, BET, TGA, DTA, and VSM. The synthesized adsorbent was used to remove lead and cadmium ions from aqueous solution. The adsorption process was improved by optimizing key parameters such as pH, adsorbent dosage, contact time, and ion concentration. For both ions, the thermodynamic data of the processes and adsorption kinetics were examined. Analyzing the experimental data revealed that the Langmuir isotherm was the most appropriate model, and the examination of adsorption kinetics showed a pseudo-second-order equation. The adsorption process by the EDTA@PD-CNT/Fe3O4 adsorbent was spontaneous and endothermic, according to the thermodynamic data, for Cd2+ and Pb2+, the highest adsorption capacities were found to be 204.54 mg g-1 and 376.48 mg g-1, respectively.

Temperature-controlled microalgal biofilm detachment and harvesting assisted by ultrasonic from 3D porous substrates grafted with thermosensitive gels

Microalgae have been renowned as the most promising energy organism with significant potential in carbon fixation. In the large-scale cultivation of microalgae, the 3D porous substrate with higher specific surface area is favorable to microalgae adsorption and biofilm formation, whereas difficult for biofilm detachment and microalgae harvesting. To solve this contradiction, N-isopropylacrylamide, a temperature-responsive gels material, was grafted onto the inner surface of the 3D porous substrate to form temperature-controllable interface wettability. The interfacial free energy between microalgae biofilm and the substrates increased from -63.02 mJ/m2 to -31.89 mJ/m2 when temperature was lowered from 32 °C to 17 °C, weakening the adsorption capacity of cells to the surface, and making the biofilm detachment ratio increased to 50.8%. When further cooling the environmental temperature to 4 °C, the detachment capability of microalgae biofilm kept growing. 91.6% of the cells in the biofilm were harvesting from the 3D porous substrate. And the biofilm detached rate was up to 19.84 g/m2/h, realizing the temperature-controlled microalgae biofilm harvesting. But, microalgae growth results in the secretion of extracellular polymeric substances (EPS), which enhanced biofilm adhesion and made cell detachment more difficult. Thus, ultrasonic vibration was used to reinforce biofilm detachment. With the help of ultrasonic vibration, microalgae biofilm detached rate increased by 143.45% to 41.07 g/m2/h. These findings provide a solid foundation for further development of microalgae biofilm detachment and harvesting technology.

Chronopotentiometric Nanopore Sensor Based on a Stimulus-Responsive Molecularly Imprinted Polymer for Label-Free Dual-Biomarker Detection

The development of sensors for detection of biomarkers exhibits an exciting potential in diagnosis of diseases. Herein, we propose a novel electrochemical sensing strategy for label-free dual-biomarker detection, which is based on the combination of stimulus-responsive molecularly imprinted polymer (MIP)-modified nanopores and a polymeric membrane chronopotentiometric sensor. The ion fluxes galvanostatically imposed on the sensing membrane surface can be blocked by the recognition reaction between the target biomarker in the sample solution and the stimulus-responsive MIP receptor in the nanopores, thus causing a potential change. By using two external stimuli (i.e., pH and temperature), the recognition abilities of the stimulus-responsive MIP receptor can be effectively modulated so that dual-biomarker label-free chronopotentiometric detection can be achieved. Using alpha fetoprotein (AFP) and prostate-specific antigen (PSA) as model biomarkers, the proposed sensor offers detection limits of 0.17 and 0.42 ng/mL for AFP and PSA, respectively.

Temperature-controlled microalgae biofilm adsorption/desorption in a thermo-responsive light-guided 3D porous photo-bioreactor for CO2 fixation

Microalgae biofilm-based culture provides an efficient CO₂ reduction and wastewater treatment method for its high photosynthetic efficiency and density. As supporting substrates for microalgae biofilm, porous materials have a big available adsorption area, but mutual shading makes it difficult to transmit external light to the internal surface for attached cells' photosynthesis. Thus, light-guided particles (SiO₂) were introduced into photosensitive resin to fabricate a light-guided ordered porous photobioreactor (PBR) by 3D printing technology in this study. The space utilization of the PBR was significantly enhanced and the effective microalgae adsorption area was increased by 13.6 times. Further, a thermo-responsive hydrogel was grafted onto the surface of the substrate to form a smart temperature-controllable interface that could enhance microalgae adsorption and desorption in both directions. When the thermo-responsive layer received light, it would generate heat due to the hydrogel's photo-thermal effect. And the surface temperature would then raise to 33 °C, higher than the hydrogel phase transition point of 32 °C, making the surface shrinking and more hydrophobicity for microalgae cells attachment. The microalgae cells' adsorption capacity increased by 103%, resulting in a high microalgae growth rate of 3.572 g m^-2 d^-1. When turning off the light, the surface temperature would cool down to below 20 °C, the surface would shrink. And the biofilm shows a 564.7% increase in desorption ability, realizing temperature-controlled microalgae harvesting.

Application of Porous Polyetheretherketone Scaffold/ Vancomycin-Loaded Thermosensitive Hydrogel Composites for Antibacterial Therapy in Bone Repair

Polyetheretherketone (PEEK) has been widely used in bone repair, but it often fails due to bacterial infection. Herein, a high-strength porous polyetheretherketone scaffold (ps-PK) loaded with antibacterial drug-loaded hydrogel strategy is proposed. The prepared ps-PK possesses high porosity (30.8%-64.7%) and the compression modulus is between 0.4-0.98 GPa. The interconnected pore-type structure endows it with a drug loading capacity. Poly(_D,L -lactic acid-co-glycolic acid)-b-Poly(ethylene glycol)-b-Poly(_D,L -lactic acid-co-glycolic acid) (PLGA-PEG-PLGA) thermoresponsive hydrogels loaded with vancomycin are used as the drug sustained-release system. The vancomycin-loaded hydrogels in the solution state at a low temperature were filled into a porous polyetheretherketone scaffold (ps-PK-VGel) and formed a gel state after implantation in vivo. The antibacterial rate of ps-PK-VGel against methicillin-resistant staphylococcus aureus (MRSA) in vitro was 99.7% and histological observation in vivo demonstrates that the ps-PK-VGel shows obvious antibacterial activity. Given its excellent antibacterial ability and mechanical properties, the porous PEEK scaffold composite drug-loaded thermosensitive hydrogel has great potential in bone repair surgery applications. This article is protected by copyright. All rights reserved.

Development of temperature-responsive polymeric gels with physical crosslinking due to intermolecular 𝜋-𝜋 interactions

Poly(N-isopropylacrylamide) PNIPAAm was polymerized with co-monomers containing a biphenyl moiety to create a unique thermoresponsive physically crosslinked system due to the presence of pi-pi interactions between the biphenyl moieties. The biphenyl monomers used were 2-phenylphenol monoacrylate (2PPMA) and 4-phenylphenol monoacrylate (4PPMA). These monomers were utilized to synthesize a set of polymers with biphenyl monomer (2PPMA/4PPMA) content from 2.5 to 7.5 mole percent and with initiator concentrations from 0.1 and 1.0 weight percent. The resulting polymers were characterized by various techniques, such as gel permeation chromatography (GPC), swelling studies and mechanical testing. The decrease in the average molecular weight of the polymers due to the increase in the concentration of initiator was confirmed by GPC results. Swelling studies confirmed the expected temperature dependent swelling properties and explored the impact of the biphenyl comonomers. These studies indicated that with the increase in biphenyl comonomers, the physical crosslinking increases which leads to decrease in the swelling ratio. The results from the mechanical tests also depict the effect of the concentration of biphenyl comonomers. These physically crosslinked polymeric systems with their unique properties have potential applications spanning environmental remediation/sensing, biomedicine, etc.

Synthesis of an Enzyme-Mediated Reversible Cross-linked Hydrogel for Cell Culture

Detachment of fragile cell types cultured on two-dimensional (2D) surfaces has been shown to be detrimental to their viability. For example, detachment of induced pluripotent stem cell (iPSC)-derived neurons grown in vitro in 2D typically results in loss of neuronal connections and/or cell death. Avoiding cell detachment altogether by changing the properties of the substrate on which the cells are grown is a compelling strategy to maintain cell viability. Here, we present the synthesis of a reversible cross-linked hydrogel that is sufficiently stable for cell culture and differentiation and is cleaved by an external stimulus, facilitating injection. Specifically, hyaluronan (HA) and methylcellulose (MC) were modified with ketone and aldehyde groups, respectively, and a TEV protease-degradable peptide was synthesized via solid-state synthesis and modified at both termini with oxyamine groups to cross-link HA-ketone and MC-aldehyde to produce oxime-cross-linked HA × MC. The HA × MC hydrogel demonstrated good stability, enzyme-sensitive degradation, and cytocompatibility with iPSC-derived neural progenitor cells, laying the framework for broad applicability.

Multifunctional Thermoresponsive Microcarriers for High-Throughput Cell Culture and Enzyme-Free Cell Harvesting

An effective treatment of human diseases using regenerative medicine and cell therapy approaches requires a large number of cells. Cultivation of cells on microcarriers is a promising approach due to the high surface-to-volume ratios that these microcarriers offer. Here, multifunctional temperature-responsive microcarriers (cytoGel) made of an interpenetrating hydrogel network composed of poly(N-isopropylacrylamide) (PNIPAM), poly(ethylene glycol) diacrylate (PEGDA), and gelatin methacryloyl (GelMA) are developed. A flow-focusing microfluidic chip is used to produce microcarriers with diameters in the range of 100-300 μm and uniform size distribution (polydispersity index of ≈0.08). The mechanical properties and cells adhesion properties of cytoGel are adjusted by changing the composition hydrogel composition. Notably, GelMA regulates the temperature response and enhances microcarrier stiffness. Human-derived glioma cells (U87) are grown on cytoGel in static and dynamic culture conditions with cell viabilities greater than 90%. Enzyme-free cell detachment is achieved at room temperature with up to 70% detachment efficiency. Controlled release of bioactive molecules from cytoGel is accomplished for over a week to showcase the potential use of microcarriers for localized delivery of growth factors to cell surfaces. These microcarriers hold great promise for the efficient expansion of cells for the industrial-scale culture of therapeutic cells.

Thermoresponsive Surfaces Grafted by Shrinkable Hydrogel Poly(N-isopropylacrylamide) for Controlling Microalgae Cells Adhesion during Biofilm Cultivation

Microalgae is a promising candidate for reducing greenhouse gas and producing renewable biofuels. For microalgae biofilm cultivation, a strong adhesion ability of microalgae cells onto the surface is a prerequisite to resist the fluid shear stress, while strong adhesion is not of benefit to the biofilm harvesting process. To solve this dilemma, a thermoresponsive surface (TMRS) with lower critical solution temperature of 33 °C was made by grafting N-isopropylacrylamide onto a silicate glass slide. The wettability of the TMRS changed from hydrophilic (contact angle of 59.4°) to hydrophobic (contact angle of 91.6°) when the temperature rose from 15 to 35 °C, resulting in the increase of adhesion energy of the TMRS to Chlorella vulgaris cells by 135.6%. The experiments showed that the cells were more likely to attach onto the TMRS at the higher temperature of 35 °C owing to the surface microstructures generated by the hydrogel layer shrinkage, which is similar in size to the microalgae cells. And the cell coverage rate on TMRS increased by 32% compared to the original glass surface. Conversely, the cells separate easily from the TMRS at a lower temperature of 15 °C, and the cell adhesion density was reduced by 19% due to hydrogel layer swelling to a relatively flat surface.

Development of stimuli-responsive intelligent polymer micelles for the delivery of doxorubicin

Doxorubicin is still used as a first-line drug in current therapeutics for numerous types of malignant tumours (including lymphoma, transplantable leukaemia and solid tumour). Nevertheless, to overcome the serious side effects like cardiotoxicity and myelosuppression caused by effective doses of doxorubicin remains as a world-class puzzle. In recent years, the usage of biocompatible polymeric nanomaterials to form an intelligently sensitive carrier for the targeted release in tumour microenvironment has attracted wide attention. These different intelligent polymeric micelles (PMs) could change the pharmacokinetics process of drugs or respond in the special microenvironment of tumour site to maximise the efficacy and reduce the toxicity of doxorubicin in other tissues and organs. Several intelligent PMs have already been in the clinical research stage and planned for market. Therefore, related research remains active, and the latest nanotechnology approaches for doxorubicin delivery are always in the spotlight. Centring on the model drugs doxorubicin, this review summarised the mechanisms of PMs, classified the polymers used in the application of doxorubicin delivery and discussed some interesting and imaginative smart PMs in recent years.

The design of a thermoresponsive surface for the continuous culture of human pluripotent stem cells

Commonly, stem cell culture is based on batch-type culture, which is laborious and expensive. We continuously cultured human pluripotent stem cells (hPSCs) on thermoresponsive dish surfaces, where hPSCs were partially detached on the same thermoresponsive dish by decreasing the temperature of the thermoresponsive dish to be below the lower critical solution temperature for only 30 min. Then, the remaining cells were continuously cultured in fresh culture medium, and the detached stem cells were harvested in the exchanged culture medium. hPSCs were continuously cultured for ten cycles on the thermoresponsive dish surface, which was prepared by coating the surface with poly(N-isopropylacrylamide-co-styrene) and oligovitronectin-grafted poly(acrylic acid-co-styrene) or recombinant vitronectin for hPSC binding sites to maintain hPSC pluripotency. After ten cycles of continuous culture on the thermoresponsive dish surface, the detached cells expressed pluripotency proteins and had the ability to differentiate into cells derived from the three germ layers in vitro and in vivo. Furthermore, the detached cells differentiated into specific cell lineages, such as cardiomyocytes, with high efficiency.

Two-in-One Platform for High-Efficiency Intracellular Delivery and Cell Harvest: When a Photothermal Agent Meets a Thermoresponsive Polymer

Efficient intracellular delivery of exogenous macromolecules is a key operation in biological research and for clinical applications. Moreover, under particular in vitro or ex vivo conditions, harvesting the engineered cells that maintain good viability is also important. However, none of the methods currently available is truly satisfactory in all respects. Herein, a "two-in-one" platform based on a polydopamine/poly( N-isopropylacrylamide) (PDA/PNIPAAm) hybrid film is developed, showing high efficiency in both cargo delivery and cell harvest without compromising cell viability. Due to the strong photothermal effect of PDA in response to near-infrared irradiation, this film can deliver diverse molecules to a number of cell types (including three hard-to-transfect cells) with an efficiency of ∼99% via membrane-disruption mechanism. Moreover, due to the thermoresponsive properties of PNIPAAm, the cells are harvested from the film without compromising viability by simply decreasing the temperature. A proof-of-concept experiment demonstrates that, using this platform, "recalcitrant" endothelial cells can be transfected by the functional ZNF580 gene and the harvested transfected cells can be recultured with high retention of viability and improved migration. In general, this "two-in-one" platform provides a reliable, universally applicable approach for both intracellular delivery and cell harvest in a highly efficient and nondestructive way, with great potential for use in a wide range of biomedical applications.

Multi-Responsive Behaviors of Copolymers Bearing N-Isopropylacrylamide with or without Phenylboronic Acid in Aqueous Solution

Continuing efforts to develop novel smart materials are anticipated to upgrade the quality of life of humans. Thermo-responsive poly(N-isopropylacrylamide) and glucose-responsive phenylboronic acid-typical representatives-are often integrated as multi-stimuli-sensitive materials, but few are available for side-by-side comparisons with their properties. In this study, both copolymers bearing N-isopropylacrylamide (NIPAAm), with or without 3-acrylamidophenylboronic acid (AAPBA), were synthesized by free radical polymerization, and characterized by Fourier transform infrared spectrometry, nuclear magnetic resonance hydrogen spectroscopy and gel permeation chromatography. Dynamic light scattering was used to analyze and compare the responsive behaviors of the copolymers in different aqueous solutions. Atomic force microscopy was also employed to investigate the apparent morphology changes with particle sizes. The results demonstrated that the introduction of NIPAAm endowed the composite materials with thermosensitivity, whereas the addition of AAPBA lowered the molecular weight of the copolymers, intensified the intermolecular aggregation of the nanoparticles, reduced the lower critical solution temperature (LCST) of the composites, and accordingly allowed the copolymers to respond to glucose. It was also concluded that the responding of smart copolymers to operating parameters can be activated only under special conditions, and copolymer dimension and conformation were affected by inter/intramolecular interactions.