Ultra-Flexible, Breathable, and Robust PAN/MWCNTs/PANI Nanofiber Networks for High-Performance Wearable Gas Sensor Application.

Wearable gas sensors have drawn great attention for potential applications in health monitoring, minienvironment detection, and advanced soft electronic noses. However, it still remains a great challenge to simultaneously achieve excellent flexibility, high sensitivity, robustness, and gas permeability, because of the inherent limitation of widely used traditional organic flexible substrates. Herein, an electrospinning polyacrylonitrile (PAN) nanofiber network was designed as a flexible substrate, on which an ultraflexible wearable gas sensor was prepared with in situ assembled polyaniline (PANI) and multiwalled carbon nanotubes (MWCNTs) as a sensitive layer. The unique nanofiber network and strong binding force between substrate and sensing materials endow the wearable gas sensor with excellent robustness, flexibility, and gas permeability. The wearable sensor can maintain stable NH3 sensing performance while sustaining extreme bending and stretching (50% of strain). The Young's modulus of wearable PAN/MWCNTs/PANI sensor is as low as 18.9 MPa, which is several orders of magnitude smaller than those of reported flexible sensors. The water vapor transmission rate of the sensor is 0.38 g/(cm2 24 h), which enables the wearing comfort of the sensor. Most importantly, due to the effective exposure of sensing sites as well as the heterostructure effect between MWCNTs and PANI, the sensor shows high sensitivity to NH3 at room temperature, and the theoretical limit of detection is as low as 300 ppb. This work provides a new avenue for the realization of reliable and high-performance wearable gas sensors.

Novel electrospun-based extractive probes for rapid determination of clinically important compounds in human plasma.

BACKGROUND: Coated blade spray (CBS) represents an innovative approach that utilizes solid-phase microextraction principles for sampling and sample preparation. When combined with ambient mass spectrometry (MS), it can also serve as an electrospray ionization source. Therefore, it became a promising tool in analytical applications as it can significantly reduce the analysis time. However, the current CBS coatings are based on the immobilization of extractive particles in bulk polymeric glue, which constrains the diffusion of the analytes to reach the extractive phase; therefore, the full reward of the system cannot be taken at pre-equilibrium. This has sparked the notion of developing new CBS probes that exhibit enhanced kinetics. RESULTS: With this aim, to generate a new extractive phase with improved extraction kinetics, poly(divinylbenzene) (PDVB) nanoparticles were synthesized by mini-emulsion polymerization and then immobilized into sub-micrometer (in diameter) sized polyacrylonitrile fibers which were obtained by electrospinning method. Following the optimization and characterization studies, the electrospun-coated blades were used to determine cholesterol, testosterone, and progesterone in plasma spots using the CBS-MS approach. For testosterone and progesterone, 10 ng mL-1 limits of quantification could be obtained, which was 200 ng mL-1 for cholesterol in spot-sized samples without including any pre-treatment steps to samples prior to extraction. SIGNIFICANCE: The comparison of the initial kinetics for dip-coated and electrospun-coated CBS probes proved that the electrospinning process could enhance the extraction kinetics; therefore, it can be used for more sensitive analyses. The total analysis time with this method, from sample preparation to instrumental analysis, takes only 7 min, which suggests that the new probes are promising for fast diagnostic applications.

Optical fiber sensing probe for detecting a carcinoembryonic antigen using a composite sensitive film of PAN nanofiber membrane and gold nanomembrane.

An optical fiber sensing probe using a composite sensitive film of polyacrylonitrile (PAN) nanofiber membrane and gold nanomembrane is presented for the detection of a carcinoembryonic antigen (CEA), a biomarker associated with colorectal cancer and other diseases. The probe is based on a tilted fiber Bragg grating (TFBG) with a surface plasmon resonance (SPR) gold nanomembrane and a functionalized polyacrylonitrile (PAN) PAN nanofiber coating that selectively binds to CEA molecules. The performance of the probe is evaluated by measuring the spectral shift of the TFBG resonances as a function of CEA concentration in buffer. The probe exhibits a sensitivity of 0.46 dB/(µg/ml), a low limit of detection of 505.4 ng/mL in buffer, and a good selectivity and reproducibility. The proposed probe offers a simple, cost-effective, and a novel method for CEA detection that can be potentially applied for clinical diagnosis and monitoring of CEA-related diseases.

Shape Self-Adaptive Liquid Embolic Agent for Ultrafast and Durable Vascular Embolization.

Minimally invasive embolization greatly decreases the mortality resulting from vascular injuries while still suffering from a high risk of recanalization and systematic thrombosis due to the intrinsic hydrophobicity and poor adhesion of the clinically used liquid embolic agent of Lipiodol. In this study, a shape self-adaptive liquid embolic agent was developed by mixing biocompatible poly(acrylic acid) (PAA), two-dimensional magnesium-aluminum layered double hydroxide (LDH), and poly(ethylene glycol)200 (PEG200). Upon contact with blood, the injectable PAA-LDH@PEG200 would quickly absorb water to form an adhesive and mechanically strong PAA-LDH thin hydrogel within 5 s, which could firmly adhere to the blood vessel wall for ultrafast and durable embolization. In addition, benefiting from the "positively charged nucleic center effect" of LDH nanosheets, the liquid PAA-LDH@PEG200 could avoid vascular distension by PAA overexpansion and possess high shock-resistant mechanical strength from the blood flow. Furthermore, both in vitro and in vivo embolization experiments demonstrated the complete embolic capacity of liquid PAA-LDH@PEG200 without the occurrence of recanalization for 28 days and also the great potential to act as a platform to couple with chemotherapeutic drugs for the minimized transcatheter arterial chemoembolization (TACE) treatment of VX2 tumors without recurrence for 18 days. Thus, liquid PAA-LDH@PEG200 developed here possesses great potential to act as a shape self-adaptive liquid embolic agent for ultrafast and durable vascular embolization.

Rationally designed ß-cyclodextrin-crosslinked polyacrylamide hydrogels for cell spheroid formation and 3D tumor model construction.

In vitro tumor models are essential for understanding tumor behavior and evaluating tumor biological properties. Hydrogels that can mimic the tumor extracellular matrix have become popular for creating 3D in vitro tumor models. However, designing biocompatible hydrogels with appropriate chemical and physical properties for constructing tumor models is still a challenge. In this study, we synthesized a series of ß-cyclodextrin (ß-CD)-crosslinked polyacrylamide hydrogels with different ß-CD densities and mechanical properties and evaluated their potential for use in 3D in vitro tumor model construction, including cell capture and spheroid formation. By utilizing a combination of ß-CD-methacrylate (CD-MA) and a small amount of N,N'-methylene bisacrylamide (BIS) as hydrogel crosslinkers and optimizing the CD-MA/BIS ratio, the hydrogels performed excellently for tumor cell 3D culture and spheroid formation. Notably, when we co-cultured L929 fibroblasts with HeLa tumor cells on the hydrogel surface, co-cultured spheroids were formed, showing that the hydrogel can mimic the complexity of the tumor extracellular matrix. This comprehensive investigation of the relationship between hydrogel mechanical properties and biocompatibility provides important insights for hydrogel-based in vitro tumor modeling and advances our understanding of the mechanisms underlying tumor growth and progression.

Tumor-specific enhanced NIR-II photoacoustic imaging via photothermal and low-pH coactivated AuNR@PNIPAM-VAA nanogel.

BACKGROUND: Properly designed second near-infrared (NIR-II) nanoplatform that is responsive tumor microenvironment can intelligently distinguish between normal and cancerous tissues to achieve better targeting efficiency. Conventional photoacoustic nanoprobes are always "on", and tumor microenvironment-responsive nanoprobe can minimize the influence of endogenous chromophore background signals. Therefore, the development of nanoprobe that can respond to internal tumor microenvironment and external stimulus shows great application potential for the photoacoustic diagnosis of tumor. RESULTS: In this work, a low-pH-triggered thermal-responsive volume phase transition nanogel gold nanorod@poly(n-isopropylacrylamide)-vinyl acetic acid (AuNR@PNIPAM-VAA) was constructed for photoacoustic detection of tumor. Via an external near-infrared photothermal switch, the absorption of AuNR@PNIPAM-VAA nanogel in the tumor microenvironment can be dynamically regulated, so that AuNR@PNIPAM-VAA nanogel produces switchable photoacoustic signals in the NIR-II window for tumor-specific enhanced photoacoustic imaging. In vitro results show that at pH 5.8, the absorption and photoacoustic signal amplitude of AuNR@PNIPAM-VAA nanogel in NIR-II increases up obviously after photothermal modulating, while they remain slightly change at pH 7.4. Quantitative calculation presents that photoacoustic signal amplitude of AuNR@PNIPAM-VAA nanogel at 1064 nm has ~ 1.6 folds enhancement as temperature increases from 37.5 °C to 45 °C in simulative tumor microenvironment. In vivo results show that the prepared AuNR@PNIPAM-VAA nanogel can achieve enhanced NIR-II photoacoustic imaging for selective tumor detection through dynamically responding to thermal field, which can be precisely controlled by external light. CONCLUSIONS: This work will offer a viable strategy for the tumor-specific photoacoustic imaging using NIR light to regulate the thermal field and target the low pH tumor microenvironment, which is expected to realize accurate and dynamic monitoring of tumor diagnosis and treatment.

Photothermally responsive graphene hybrid dry powders for diabetic wound healing.

The treatment of diabetic wounds remains a significant challenge in the medical field. In this study, we present a novel approach using photothermally responsive graphene hybrid dry powders for the treatment of diabetic wounds. These powders, derived from polyacrylic acid (PAA) and polyethyleneimine (PEI), exhibit rapid water absorption at the interface, leading to thein situformation of physically crosslinked hydrogels due to interactions between polymers. Furthermore, by incorporating graphene into the PAA/PEI powder mixture, we establish a multifunctional platform with capabilities such as photothermal antibacterial effects and drug release. Given the outstanding performance of this hybrid material, we demonstrate its potential in wound healing by incorporating the tumor necrosis factor-alpha (TNF-α) inhibitor Etanercept into the PAA/PEI powder. This intervention resulted in a significant improvement in the wound healing process in diabetic rats, as evidenced by the downregulation of inflammatory factors, promotion of collagen deposition, and enhanced vascularization. These remarkable attributes underscore the enormous potential value of the presented hydrogel patches in the field of biomedicine.

Molecular and microbial insights towards anaerobic biodegradation of anionic polyacrylamide in oil sands tailings.

Anionic polyacrylamide (A-PAM) is widely used as a flocculant in the management of oil sands tailings. Nevertheless, apprehensions arise regarding its potential biodegradation and environmental consequences within the context of oil sands tailings. Consequently, it is imperative to delve into the anaerobic biodegradation of A-PAM in oil sands tailings to gain a comprehensive understanding of its influence on tailings water quality. This work explored the dynamics of A-PAM biodegradation across concentrations: 50, 100, 250, 500, 1000, and 2000 mg/kg TS. The results showed a significant decrease in A-PAM concentration and molecular weight at lower concentrations (50 and 100 mg/kg TS) compared to higher ones, suggesting enhanced degradation efficiency. Likewise, the organic transformation and methane production exhibited dependency on A-PAM concentrations. The peak concentrations observed were 20.0 mg/L for volatile fatty acids (VFAs), 0.07 mg/L for acrylamide (AMD), and 8.9 mL for methane yield, with these maxima being recorded at 50 mg/kg TS. The biodegradation efficiency diminishes at higher concentrations of A-PAM, potentially due to the inhibitory effects of polyacrylic acid accumulation. A-PAM biodegradation under anaerobic condition did not contribute to acute toxicity or genotoxicity. SEM-EDS, FT-IR and XRD analyses further revealed that higher concentrations of A-PAM inhibited the biodegradation by altering floc structure and composition, thereby restricting the microbial activity. Major microorganisms, including Smithella, Candidatus_Cloacimonas, W5, XBB1006, and DMER64 were identified, highlighting A-PAM's dual role as a source of carbon and nitrogen under anaerobic conditions. The above findings from this research not only significantly advance understanding of A-PAM's environmental behavior but also contribute to the effective management practices in oil sands tailings.

Active targeting microemulsion-based thermosensitive hydrogel against periodontitis by reconstructing Th17/Treg homeostasis via regulating ROS-macrophages polarization cascade.

Periodontitis is a multifactorial inflammatory disease characterized by severe alveolar bone damage and attachment loss. The imbalance of T help 17 (Th17) / regulatory T cells (Treg) induces excessive interleukin (IL)-17, which leads to alveolar bone damage and aggravates the development of periodontitis. Therefore, we proposed a therapeutic strategy to restore Th17/Treg homeostasis by interfering reactive oxygen species (ROS)-macrophage polarization cascade using active targeting microemulsions-based thermosensitive hydrogel. Folic acid-modified quercetin-loaded microemulsions (FA-Qu-MEs) were dispersed in poloxamer 407 and poly(N-isopropylacrylamide) matrix of hydrogel (FA-Qu-MEs@Gel). FA-Qu-MEs@Gel could be locally injected into the periodontal pocket and sustainedly release drugs. FA-Qu-MEs exhibited excellent ROS scavenging potency by targeting macrophages, resulting M1 phenotype macrophage from to M2 phenotype macrophage. Subsequently, the phenotypic changes of macrophages lead to decreased expression of IL-6 and tumor necrosis factor-α, which inhibited activated Th17, while IL-10 secreted by M2 macrophages promoted Treg differentiation. Finally, the restored Th17/Treg homeostasis reduced the level of IL-17 to accelerate alveolar bone regeneration. This study deigns a novel system that promote alveolar bone regeneration by remodeling Th17/Treg homeostasis via regulating ROS-macrophages polarization cascade for periodontitis treatment.

Hydrogels composite optimized for low resistance and loading-unloading hysteresis for flexible biosensors.

With the advancement of wearable and implantable medical devices, hydrogel flexible bioelectronic devices have attracted significant interest due to exhibiting tissue-like mechanical compliance, biocompatibility, and low electrical resistance. In this study, the development and comprehensive performance evaluation of poly(acrylic acid)/ N,N'-bis(acryloyl) cystamine/ 1-butyl-3-ethenylimidazol-1-ium:bromide (PAA/NB/IL) hydrogels designed for flexible sensor applications are introduced. Engineered through a combination of physical and chemical cross-linking strategies, these hydrogels exhibit strong mechanical properties, high biocompatibility, and effective sensing capabilities. At 95 % strain, the compressive modulus of PAA/NB/IL 100 reach up to 3.66 MPa, with the loading-unloading process showing no significant hysteresis loop, indicating strong mechanical stability and elasticity. An increase in the IL content was observed to enlarge the porosity of the hydrogels, thereby influencing their swelling behavior and sensing functionality. Biocompatibility assessments revealed that the hemolysis rate was below 5 %, ensuring their suitability for biomedical applications. Upon implantation in rats, a minimal acute inflammatory response was observed, comparable to that of the biocompatibility control poly(ethylene glycol) diacrylate (PEGDA). These results suggest that PAA/NB/IL hydrogels hold promise as biomaterials for biosensors, offering a balance of mechanical integrity, physiological compatibility, and sensing sensitivity, thereby facilitating advanced healthcare monitoring solutions.

Targeted photodynamic therapy technique of Janus nanoparticles on breast cancer.

Spherical gold/polyacrylic acid (Au/PAA) polymer-inorganic Janus nanoparticles (JNPs) with simultaneous therapeutic and targeting functions were fabricated. The obtained Au/PAA JNPs were further selectively functionalized with folic acid (FA) and thiol PEG amine (SH-PEG-NH2) on Au sides to provide superior biocompatibility and active targeting, while the other PAA sides were loaded with 5-aminolevulinic acid (5-ALA) to serve as a photosensitizer (PS) for photodynamic therapeutic (PDT) effects on MCF-7 cancer cells. The PS loading of 5-ALA was found to be 83% with an average hydrodynamic size and z-potential of 146 ± 0.8 nm and -6.40 mV respectively for FA-Au/PAA-ALA JNPs. The in vitro PDT study of the JNPs on MCF-7 breast cancer cells under 636 nm laser irradiation indicated the cell viability of 24.7% ± 0.5 for FA-Au/PAA-ALA JNPs at the IC50 value of 0.125 mM. In this regard, the actively targeted FA-Au/PAA-ALA JNPs treatment holds great potential for tumour therapy with high cancer cell-killing efficacy.

Bioinspired Photoelectronic Synergy Coating with Antifogging and Antibacterial Properties.

Optically transparent glass with antifogging and antibacterial properties is in high demand for endoscopes, goggles, and medical display equipment. However, many of the previously reported coatings have limitations in terms of long-term antifogging and efficient antibacterial properties, environmental friendliness, and versatility. In this study, inspired by catfish and sphagnum moss, a novel photoelectronic synergy antifogging and antibacterial coating was prepared by cross-linking polyethylenimine-modified titanium dioxide (PEI-TiO2), polyvinylpyrrolidone (PVP), and poly(acrylic acid) (PAA). The as-prepared coating could remain fog-free under hot steam for more than 40 min. The experimental results indicate that the long-term antifogging properties are due to the water absorption and spreading characteristics. Moreover, the organic-inorganic hybrid of PEI and TiO2 was first applied to enhance the antibacterial performance. The Staphylococcus aureus and the Escherichia coli growth inhibition rates of the as-prepared coating reached 97 and 96% respectively. A photoelectronic synergy antifogging and antibacterial mechanism based on the positive electrical and photocatalytic properties of PEI-TiO2 was proposed. This investigation provides insight into designing multifunctional bioinspired surface materials to realize antifogging and antibacterial that can be applied to medicine and daily lives.

Third-Generation Anticancer Photodynamic Therapy Systems Based on Star-like Anionic Polyacrylamide Polymer, Gold Nanoparticles, and Temoporfin Photosensitizer.

Photodynamic therapy (PDT) is a non-invasive anticancer treatment that uses special photosensitizer molecules (PS) to generate singlet oxygen and other reactive oxygen species (ROS) in a tissue under excitation with red or infrared light. Though the method has been known for decades, it has become more popular recently with the development of new efficient organic dyes and LED light sources. Here we introduce a ternary nanocomposite: water-soluble star-like polymer/gold nanoparticles (AuNP)/temoporfin PS, which can be considered as a third-generation PDT system. AuNPs were synthesized in situ inside the polymer molecules, and the latter were then loaded with PS molecules in an aqueous solution. The applied method of synthesis allows precise control of the size and architecture of polymer nanoparticles as well as the concentration of the components. Dynamic light scattering confirmed the formation of isolated particles (120 nm diameter) with AuNPs and PS molecules incorporated inside the polymer shell. Absorption and photoluminescence spectroscopies revealed optimal concentrations of the components that can simultaneously reduce the side effects of dark toxicity and enhance singlet oxygen generation to increase cancer cell mortality. Here, we report on the optical properties of the system and detailed mechanisms of the observed enhancement of the phototherapeutic effect. Combinations of organic dyes with gold nanoparticles allow significant enhancement of the effect of ROS generation due to surface plasmonic resonance in the latter, while the application of a biocompatible star-like polymer vehicle with a dextran core and anionic polyacrylamide arms allows better local integration of the components and targeted delivery of the PS molecules to cancer cells. In this study, we demonstrate, as proof of concept, a successful application of the developed PDT system for in vitro treatment of triple-negative breast cancer cells under irradiation with a low-power LED lamp (660 nm). We consider the developed nanocomposite to be a promising PDT system for application to other types of cancer.

Co-delivery of carboplatin and doxorubicin using ZIF-8 coated chitosan-poly(N-isopropyl acrylamide) nanoparticles through a dual pH/thermo responsive strategy to breast cancer cells.

A dual pH/temperature sensitive core-shell nanoformulation has been developed based on ZIF-8 coated with chitosan-poly(N-isopropyl acrylamide) (CS-PNIPAAm) for co-delivery of doxorubicin (DOX) and carboplatin (CBP) in breast cancer cells. The resulting nanoparticles (NPs) had particle sizes around 200 nm and a zeta potential of about +30 mV. The CBP and DOX loading contents in the final NPs were 11.6 % and 55.54 %, respectively. NPs showed a pH and thermoresponsive drug release profile with a sustained prolonged release under physiological conditions. The in vitro cytotoxicity experiments showed a significant synergism of CBP and DOX to induce the IC50 of 1.96 µg/mL in MCF-7 cells and 4.54 µg/mL in MDA-MB-231 cells. Also, the final NPs were safer than free DOX and CBP on normal cells. The in vitro study confirmed the higher potency of the designed NPs in combination therapy against breast cancer cells with lower side effects than free drugs.

Janus Membrane-Based Wearable pH Sensor with Sweat Absorption, Gas Permeability, and Self-Adhesiveness.

Wearable biomedical sensors have enabled noninvasive and continuous physiological monitoring for daily health management and early detection of chronic diseases. Among biomedical sensors, wearable pH sensors attracted significant interest, as pH influences most biological reactions. However, conformable pH sensors that have sweat absorption ability, are self-adhesive to the skin, and are gas permeable remain largely unexplored. In this study, we present a pioneering approach to this problem by developing a Janus membrane-based pH sensor with self-adhesiveness on the skin. The sensor is composed of a hydrophobic polyurethane-polydimethylsiloxane porous hundreds nanometer-thick substrate and a hydrophilic poly(vinyl alcohol)-poly(acrylic acid) porous nanofiber layer. This Janus membrane exhibits a thickness of around 10 µm, providing a conformable adhesion to the skin. The simultaneous realization of solution absorption, gas permeability, and self-adhesiveness makes it suitable for long-term continuous monitoring without compromising the comfort of the wearer. The pH sensor was tested successfully for continuous monitoring for 7.5 h, demonstrating its potential for stable analysis of skin health conditions. The Janus membrane-based pH sensor holds significant promise for comprehensive skin health monitoring and wearable biomedical applications.

An Innovative Approach for Tailoring Molecularly Imprinted Polymers for Biosensors-Application to Cancer Antigen 15-3.

This work presents a novel approach for tailoring molecularly imprinted polymers (MIPs) with a preliminary stage of atom transfer radical polymerization (ATRP), for a more precise definition of the imprinted cavity. A well-defined copolymer of acrylamide and N,N'-methylenebisacrylamide (PAAm-co-PMBAm) was synthesized by ATRP and applied to gold electrodes with the template, followed by a crosslinking reaction. The template was removed from the polymer matrix by enzymatic/chemical action. The surface modifications were monitored via electrochemical impedance spectroscopy (EIS), having the MIP polymer as a non-conducting film designed with affinity sites for CA15-3. The resulting biosensor exhibited a linear response to CA15-3 log concentrations from 0.001 to 100 U/mL in PBS or in diluted fetal bovine serum (1000×) in PBS. Compared to the polyacrylamide (PAAm) MIP from conventional free-radical polymerization, the ATRP-based MIP extended the biosensor's dynamic linear range 10-fold, improving low concentration detection, and enhanced the signal reproducibility across units. The biosensor demonstrated good sensitivity and selectivity. Overall, the work described confirmed that the process of radical polymerization to build an MIP material influences the detection capacity for the target substance and the reproducibility among different biosensor units. Extending this approach to other cancer biomarkers, the methodology presented could open doors to a new generation of MIP-based biosensors for point-of-care disease diagnosis.

Fabrication and evaluation of stable amorphous polymer-drug composite particles via a nozzle-free ultrasonic nebulizer.

We present a promising method for producing amorphous drug particles using a nozzle-free ultrasonic nebulizer with polymers, specifically polyvinylpyrrolidone (PVP), poly(acrylic acid) (PAA), and Eudragit® S 100 (EUD). Model crystalline phase drugs-Empagliflozin, Furosemide, and Ilaprazole-are selected. This technique efficiently produces spherical polymer-drug composite particles and demonstrates enhanced stability against humidity and thermal conditions, compared to the drug-only amorphous particles. The composite particles exhibit improved water dissolution compared to the original crystalline drugs, indicating potential bioavailability enhancements. While there are challenges, including the need for continuous water supply for ultrasonic component cooling, dependency on the solubility of polymers and drugs in volatile organic solvents, and mildly elevated temperatures for solvent evaporation, our method offers significant advantages over traditional approaches. It provides a straightforward, flexible process adaptable to various drug-polymer combinations and consistently yields spherical amorphous solid dispersion (ASD) particles with a narrow size distribution. These attributes make our method a valuable advancement in pharmaceutical drug formulation and delivery.

Chitosan-PNIPAM Thermogel Associated with Hydrogel Microspheres as a Smart Formulation for MSC Injection.

Regenerative medicine based on cell therapy has emerged as a promising approach for the treatment of various medical conditions. However, the success of cell therapy heavily relies on the development of suitable injectable hydrogels that can encapsulate cells and provide a conducive environment for their survival, proliferation, and tissue regeneration. Herein, we address the medical need for cyto- and biocompatible injectable hydrogels by reporting on the synthesis of a hydrogel-forming thermosensitive copolymer. The copolymer was synthesized by grafting poly(N-isopropylacrylamide-co-carboxymethyl acrylate) (PNIPAM-COOH) onto chitosan through amide coupling. This chemical modification resulted in the formation of hydrogels that exhibit a sol-gel transition with an onset at approximately 27 °C, making them ideal for use in injectable applications. The hydrogels supported the survival and proliferation of cells for several days, which is critical for cell encapsulation. Furthermore, the study evaluates the addition of collagen/chitosan hybrid microspheres to support the adhesion of mesenchymal stem cells within the hydrogels. Altogether, these results demonstrate the potential of the PNIPAM-chitosan thermogel for cell encapsulation and its possible applications in regenerative medicine.

Effect of different surface roughening treatment on polyether ether ketone and acrylic resin bonding: A pilot study.

BACKGROUND: As polyether ether ketone (PEEK) is a relatively new material in dentistry, its bonding properties with regard to dental acrylic base materials are not fully known. To ensure the long-term success of removable dentures with a PEEK framework, the base materials must be well bonded to each other. OBJECTIVES: The study aimed to investigate the effects of different kinds of surface roughening treatment on PEEK and acrylic resin bonding. MATERIAL AND METHODS: Eighty PEEK specimens (N = 80) were randomly divided into 5 groups (n = 16 per group) and subjected to various surface roughening treatment (control, grinding, sandblasting, tribochemical silica coating (CoJet), and sulfuric acid etching). Heat-polymerized acrylic resin was applied to the treated surfaces of the PEEK specimens. The shear bond strength (SBS) test, environmental scanning electron microscopy (ESEM) analysis and three-dimensional (3D) surface topography analysis were performed. The statistical analysis of the data was conducted using the analysis of variance (ANOVA) and Tukey's multiple comparison test. RESULTS: The one-way ANOVA showed significant differences in the SBS values between the groups (p = 0.001). Sandblasting, tribochemical silica coating and sulfuric acid etching resulted in high SBS values (p = 0.001). The highest SBS values were observed in the sulfuric acid etching group (8.83 ±3.63 MPa), while the lowest SBS values were observed in the control group (3.33 ±2.50 MPa). CONCLUSIONS: The additional roughening treatment applied to the PEEK surface increases the bond strength with heat-polymerized acrylic resin.

High-throughput viscoelastic characterization of cells in hyperbolic microchannels.

Extensive research has demonstrated the potential of cell viscoelastic properties as intrinsic indicators of cell state, functionality, and disease. For this, several microfluidic techniques have been developed to measure cell viscoelasticity with high-throughput. However, current microchannel designs introduce complex stress distributions on cells, leading to inaccuracies in determining the stress-strain relationship and, consequently, the viscoelastic properties. Here, we introduce a novel approach using hyperbolic microchannels that enable precise measurements under a constant extensional stress and offer a straightforward stress-strain relationship, while operating at a measurement rate of up to 100 cells per second. We quantified the stresses acting in the channels using mechanical calibration particles made from polyacrylamide (PAAm) and found that the measurement buffer, a solution of methyl cellulose and phosphate buffered saline, shows strain-thickening following a power law up to 200 s-1. By measuring oil droplets with varying viscosities, we successfully detected changes in the relaxation times of the droplets and our approach could be used to get the interfacial tension and viscosity of liquid-liquid droplet systems from the same measurement. We further applied this methodology to PAAm microgel beads, demonstrating the accurate recovery of Young's moduli and the near-ideal elastic behavior of the beads. To explore the influence of altered cell viscoelasticity, we treated HL60 human leukemia cells with latrunculin B and nocodazole, resulting in clear changes in cell stiffness while relaxation times were only minimally affected. In conclusion, our approach offers a streamlined and time-efficient solution for assessing the viscoelastic properties of large cell populations and other microscale soft particles.