Temperature-responsive Behavior Research Articles

Thermo-responsive composite nanoparticles based on hydroxybutyl chitosan oligosaccharide: Fabrication, stimulus release and cancer therapy

Designing thermo-responsive nanocarriers based on biopolymers is fascinating and challenging for cancer therapy. In this study, thermo-responsive composite nanoparticles (CNPs) were prepared using hydroxybutyl chitosan oligosaccharide (HBCOS) and sodium caseinate (SC) via electrostatic interactions and covalent crosslinking. The temperature-responsive behaviors of CNPs were induced by the breakage of hydrogen bonds and the shrinkage of chains in nanoparticles. The CNPs exhibited concentration-independent thermo-responsive behavior, non-adsorption aggregation, and non-hemolysis, suggesting excellent stability and thermo-sensitivity. The initial release rate and final amount of DOX released from CNPs at 42 °C were higher than that at 37 °C, showing a thermo-responsive release, which was also more prominent at lower pH. The release of DOX from CNPs followed first order kinetics based on Fickian diffusion. In vitro cytotoxicity assays confirmed the thermo-responsive antitumor activity of DOX-loaded CNPs as the HT-29 cell viability incubated with DOX-loaded CNPs at 42 °C was significantly lower than that at 37 °C. Cellular uptake experiments proved that DOX-loaded CNPs accumulated in the cytoplasm after being endocytosed and promoted DOX release by increasing environment temperature. This study generated stable thermo-sensitive CNPs based on biopolymers, which can be used as potential nanocarriers for the controlled release of anticancer drugs for cancer therapy.

Tuning Structural Organization via Molecular Design and Hierarchical Assembly to Develop Supramolecular Thermoresponsive Hydrogels.

The cellular microenvironment is composed of a dynamic hierarchical fibrillar architecture providing a variety of physical and bioactive signals to the surrounding cells. This dynamicity, although common in biology, is a challenge to control in synthetic matrices. Here, responsive synthetic supramolecular monomers were designed that are able to assemble into hierarchical fibrous structures, combining supramolecular fiber formation via hydrogen bonding interactions, with a temperature-responsive hydrophobic collapse, resulting in cross-linking and hydrogel formation. Therefore, amphiphilic molecules were synthesized, composed of a hydrogen bonding ureido-pyrimidinone (UPy) unit, a hydrophobic alkyl spacer, and a hydrophilic oligo(ethylene glycol) tail. The temperature responsive behavior was introduced by functionalizing these supramolecular amphiphiles with a relatively short poly(N-isopropylacrylamide) (PNIPAM) chain (M n ∼ 2.5 or 5.5 kg/mol). To precisely control the assembly of these monomers, the length of the alkyl spacer between the UPy moiety and PNIPAM was varied in length. A robust sol-gel transition, with the dodecyl UPy-PNIPAM molecule, was obtained, with a network elasticity enhancing over 2000 times upon heating above room temperature. The UPy-PNIPAM compounds with shorter alkyl spacers were already hydrogels at room temperature. The sol-gel transition of the dodecyl UPy-PNIPAM hydrogelator could be tuned by the incorporation of different UPy-functionalized monomers. Furthermore, we demonstrated the suitability of this system for microfluidic cell encapsulation through a convenient temperature sol-gel transition. Our results indicate that this novel thermoresponsive supramolecular system offers a modular platform to study and guide single-cell behavior.

Syngas production via microwave-assisted Dry Reforming of Methane over NiFe/MgAl2O4 alloy catalyst

Dry reforming of methane (DRM) represents a promising avenue for generating syngas while simultaneously reducing CO2 emissions. However, its industrial application has been constrained by the necessity for elevated temperatures to prevent coke. Microwave (MW)-assisted DRM emerges as a compelling solution to facilitate high-temperature reactions, capitalizing on surplus renewable electrons to heat the catalyst bed swiftly and selectively, thereby circumventing the inefficient heating of the entire reactor. In this study, DRM is conducted under MW irradiation using NiFe/MgAl2O4 alloy catalysts. The impacts of MW power and catalysts' temperature-response behavior are investigated as well as the active components (Ni and Fe), and space velocity on the DRM reaction are explored. We determined the optimal quantities of Fe and Ni necessary to achieve the desired balance between MW heating and driving the DRM reaction. Under specific conditions—Ni content at 25 wt%, Fe content at 40 wt%, MW power of 286 W g−1, a temperature of 700 °C, flow rate of 450 mL min−1 and a space velocity of 12857 mL·g−1·hr−1—conversion rates of 85 % for CH4 and 62 % for CO2 are achieved. NiFe/MgAl2O4 catalysts demonstrated high potential to be used in the MW-driven DRM as compared to conventional electric heating methods.

Atomistic Molecular Dynamics Simulations of ABA-Type Polymer Peptide Conjugates: Insights into Supramolecular Structures and their Circular Dichroism Spectra.

A combination of atomistic molecular dynamics (aMD) simulations and circular dichroism (CD) analysis is used to explore supramolecular structures of amphiphilic ABA-type triblock polymer peptide conjugates (PPC). Using the example of a recently introduced PPC with pH- and temperature responsive self-assembling behavior [Otter etal., Macromolecular Rapid Communications 2018, 39, 1800459], this study shows how molecular dynamics simulations of simplified fragment molecules can add crucial information to CD data, which helps to correctly identify the self-assembled structures and monitor the folding/unfolding pathways of the molecules. The findings offer insights into the nature of structural transitions induced by external stimuli, thus contributing to the understanding of the connection of microscopic structures with macroscopicproperties.

A Comparative Study of "Grafting to" and "Grafting from" Conjugation Methods for the Preparation of Antibody-Temperature-Responsive Polymer Conjugates.

Early diagnosis of infectious diseases is still challenging particularly in a nonlaboratory environment or limited resources areas. Thus, sensitive, inexpensive, and easily handled diagnostic approaches are required. The lateral flow immunoassay (LFIA) is commonly used in the screening of infectious diseases despite its poor sensitivity, especially with low pathogenic loads (early stages of infection). This article introduces a novel polymeric material that might help in the enrichment and concentration of pathogens to overcome the LFIA misdiagnosis. To achieve this, we evaluated the efficiency of introducing poly(N-isopropylacrylamide) (PNIPAAm) into immunoglobulin G (IgG) as a model antibody using two different conjugation methods: grafting to (GT) and grafting from (GF). The IgG-PNIPAAm conjugates were characterized using SDS-PAGE, DLS, and temperature-responsive phase transition behavior. SDS-PAGE analysis revealed that the GF method was more efficient in introducing the polymer than the GT method, with calculated polymer introduction ratios of 61% and 34%, respectively. The GF method proved to be less susceptible to steric hindrance and more efficient in introducing high-molecular-weight polymers into proteins. These results are consistent with previous studies comparing the GT and GF methods in similar systems. This study represents an important step toward understanding how the choice of polymer incorporation method affects the properties of IgG-PNIPAAm conjugates. The synthesized polymer allowed binding and enrichment of mouse IgG that was used as a model antigen with a clear LFIA band. On the basis of our findings, this system might help in improving the sensitivity of simple diagnostics.

Preparation and Performance Study of HTPB-g-(PNIPAM/PEG) Thermoresponsive Polymer Brush.

In recent years, a great deal of work has been devoted to the development of thermoresponsive polymers that can be made into new types of smart materials. In this paper, a branched polymer, HTPB-g-(PNIPAM/PEG), with polyolefin chain segments as the backbone and having polyethylene glycol (PEG) and poly(N-isopropylacrylamide) (PNIPAM) as side chains was synthesized by ATRP and click reactions using N3-HTPB-Br as the macroinitiator. This initiator was designed and synthesized using hydroxyl-terminated polybutadiene (HTPB) as the substrate. The temperature-responsive behavior of the branched polymer was investigated. The lower critical solution temperature (LCST) of the branched polymer was determined by ultraviolet and visible spectrophotometry (UV-vis) and was found to be 35.2 °C. The relationship between the diameter size of micelles and temperature was determined by dynamic light scattering (DLS). It was found that the diameter size changed at 36 °C, which was nearly consistent with the result obtained by UV-vis. The results of the study indicate that HTPB-g-(PNIPAM/PEG) is a temperature-responsive polymer. At room temperature, the polymer can self-assemble into composite micelles, with the main chain as the core and the branched chain as the shell. When the temperature was increased beyond LCST, the polyolefin main chain along with the PNIPAM branched chain assembled to form the nucleus, and the PEG branched chain constituted the shell.

Fire behavior and post-fire residual tensile strength prediction of carbon fiber/phthalonitrile composite laminates

Carbon fiber/phthalonitrile (Cf/PN) composite has a high potential for applications in the aerospace sector because of the outstanding heat and flame resistance of phthalonitrile resin. Here we aim to evaluate the fire behavior of Cf/PN laminate under localized one-sided flame heating as well as the residual tensile performance. The residual tensile strength after quasi-isothermal pyrolysis in an inert environment decreases linearly with the increase in the pyrolysis degree. The temperature response and pyrolysis behavior are analyzed through a combination of experiments and finite element simulations, and the damage mode of the laminate structure is concluded through morphological observation after flame exposure and the surface axial strain field using digital image correlation. Eventually, the residual tensile strength of laminates with different thicknesses after different times of flame exposure was effectively predicted based on the numerical simulated pyrolysis degree distribution. This research supplies fundamental test data on the mechanical properties of Cf/PN laminates and is expected to provide guidelines for the engineering application of Cf/PN composites in thermal protection/load-bearing all-in-one structures.

Effect of Tannic Acid Concentrations on Temperature-Sensitive Sol-Gel Transition and Stability of Tannic Acid/Pluronic F127 Composite Hydrogels.

Recently, interest in polyphenol-containing composite adhesives for various biomedical applications has been growing. Tannic acid (TA) is a polyphenolic compound with advantageous properties, including antioxidant and antimicrobial properties. Additionally, TA contains multiple hydroxyl groups that exhibit biological activity by forming hydrogen bonds with proteins and biomacromolecules. Furthermore, TA-containing polymer composites exhibit excellent tissue adhesion properties. In this study, the gelation behavior and adhesion forces of TA/Pluronic F127 (TA/PluF) composite hydrogels were investigated by varying the TA and PluF concentrations. PluF (above 16 wt%) alone showed temperature-responsive gelation behavior because of the closely packed micelle aggregates. After the addition of a small amount of TA, the TA/PluF hydrogels showed thermosensitive behavior similar to that of PluF hydrogels. However, the TA/PluF hydrogels containing more than 10 wt% TA completely suppressed the thermo-responsive gelation kinetics of PluF, which may have been due to the hydrogen bonds between TA and PluF. In addition, TA/PluF hydrogels with 40 wt% TA showed excellent tissue adhesion properties and bursting pressure in porcine intestinal tissues. These results are expected to aid in understanding the use of mixtures of TA and thermosensitive block copolymers to fabricate adhesive hydrogels for versatile biomedical applications.

Fabrication of Eco-Friendly Hydrolyzed Ethylene-Maleic Anhydride Copolymer-Avermectin Nanoemulsion with High Stability, Adhesion Property, pH, and Temperature-Responsive Releasing Behaviors.

In this study, novel amphiphilic polymer emulsifiers for avermectin (Avm) were synthesized facilely via the hydrolysis of ethylene-maleic anhydride copolymer (EMA) with different agents, and their structures were confirmed by various techniques. Then, water-based Avm-nanoemulsions were fabricated with the emulsifiers via phase inversion emulsification process, and superior emulsifier was selected via the emulsification effects. Using the superior emulsifier, an optimal Avm-nanoemulsion (defined as Avm@HEMA) with satisfying particle size of 156.8 ± 4.9 nm, encapsulation efficiency (EE) of 69.72 ± 4.01% and drug loading capacity (DLC) of 54.93 ± 1.12% was constructed based on response surface methodology (RSM). Owing to the emulsifier, the Avm@HEMA showed a series of advantages, including high stability, ultraviolet resistance, low surface tension, good spreading and high affinity to different leaves. Additionally, compared to pure Avm and Avm-emulsifiable concentrate (Avm-EC), Avm@HEMA displayed a controlled releasing feature. The encapsulated Avm was released quite slowly at normal conditions (pH 7.0, 25 °C or 15 °C) but could be released at an accelerated rate in weak acid (pH 5.5) or weak alkali (pH 8.5) media or at high temperature (40 °C). The drug releasing profiles of Avm@HEMA fit the Korsmeyer-Peppas model quite well at pH 7.0 and 25 °C (controlled by Fickian diffusion) and at pH 7.0 and 10 °C (controlled by non-Fickian diffusion), while it fits the logistic model under other conditions (pH 5.5 and 25 °C, pH 8.5 and 25 °C, pH 7.0 and 40 °C).

Drug delivery in thermo-responsive silicone catheters by grafting of N-vinylcaprolactam using gamma radiation

Radiation-induced graft polymerization of poly(N-vinylcaprolactam) onto silicone catheters by direct irradiation method was studied. The effects of the irradiation dose, as well as the monomer concentration, on the grafting efficiency were studied. The conditions for achieving maximum grafting yield were observed at 30% of monomer concentration in toluene at 50 kGy. The graft polymerization was examined by different characterization methods, including measurements such as thermogravimetric analysis, infrared, water contact angle, and swelling. The temperature-responsive behavior of smart grafted copolymer was studied by swelling at different temperatures. Differently from pristine silicone catheter, the N-vinylcaprolactam-grafted catheters were able to load vancomycin and sustain the release for 30 h.Graphical abstract

Self-assembly of temperature-responsive di-block polypeptides functionalized with unnatural amino acids.

The incorporation of unnatural amino acids (uAAs) into protein-based polymers has emerged as a powerful methodology to expand their chemical repertoire. Recently, we demonstrated that incorporating uAAs into two temperature-responsive protein-based polymers-namely resilin- and elastin-like polypeptides (RLPs and ELPs, respectively)-can alter their properties. In this study, we incorporated aromatic uAAs into the protein sequence of RLP-ELP diblocks to yield new and diverse assemblies from a single DNA template. Specifically, we show that incorporating aromatic uAAs can modulate the phase-transition behaviors and self-assembly of the diblocks into various morphologies, including spherical and cylindrical micelles and single- and double-layered vesicles, with some constructs also demonstrating a temperature-responsive shape-shifting behavior. Next, we evaluated the ability of the RLP-ELP assemblies to encapsulate a chemotherapeutic drug, doxorubicin, and show how the identity of the incorporated uAAs and the morphology of the nanostructure affect the encapsulation efficiency. Taken together, our findings demonstrate that the multi-site incorporation of uAAs into temperature-responsive, amphiphilic protein-based diblock copolymers is a promising approach for the functionalization and tuning of self-assembled nanostructures.

Protein-Functionalized Gold Nanospheres with Tunable Photothermal Efficiency for the Near-Infrared Photothermal Ablation of Biofilms.

Temperature-responsive nanostructures with high antimicrobial efficacy are attractive for therapeutic applications against multidrug-resistant bacteria. Here, we report temperature-responsive nanospheres (TRNs) engineered to undergo self-association and agglomeration above a tunable transition temperature (Tt). The temperature-responsive behavior of the nanoparticles is obtained by functionalizing citrate-capped spherical gold nanoparticles (AuNPs) with elastin-like polypeptides (ELPs). Using protein design principles, we achieve a broad range of attainable Tt values and photothermal conversion efficiencies (η). Two approaches were used to adjust this range: First, by altering the position of the cysteine residue used to attach ELP to the AuNP, we attained a Tt range from 34 to 42 °C. Then, by functionalizing the AuNP with an additional small globular protein, we could extend this range to 34-50 °C. Under near-infrared (NIR) light exposure, all TRNs exhibited reversible agglomeration. Moreover, they showed an enhanced photothermal conversion efficiency in their agglomerated state relative to the dispersed state. Despite their spherical shape, TRNs have a photothermal conversion efficiency approaching that of gold nanorods (η = 68 ± 6%), yet unlike nanorods, the synthesis of TRNs requires no cytotoxic compounds. Finally, we tested TRNs for the photothermal ablation of biofilms. Above Tt, NIR irradiation of TRNs resulted in a 10,000-fold improvement in killing efficiency compared to untreated controls (p < 0.0001). Below Tt, no enhanced antibiofilm effect was observed. In conclusion, engineering the interactions between proteins and nanoparticles enables the tunable control of TRNs, resulting in a novel antibiofilm nanomaterial with low cytotoxicity.

The Effect of Block Ratio and Structure on the Thermosensitivity of Double and Triple Betaine Block Copolymers.

AB-type and BAB-type betaine block copolymers composed of a carboxybetaine methacrylate and a sulfobetaine methacrylate, PGLBT-b-PSPE and PSPE-b-PGLBT-b-PSPE, respectively, were synthesized by one-pot RAFT polymerization. By optimizing the concentration of the monomer, initiator, and chain transfer agent, block extension with precise ratio control was enabled and a full conversion (~99%) of betaine monomers was achieved at each step. Two sets (total degree of polymerization: ~300 and ~600) of diblock copolymers having four different PGLBT:PSPE ratios were prepared to compare the influence of block ratio and molecular weight on the temperature-responsive behavior in aqueous solution. A turbidimetry and dynamic light scattering study revealed a shift to higher temperatures of the cloud point and micelle formation by increasing the ratio of PSPE, which exhibit upper critical solution temperature (UCST) behavior. PSPE-dominant diblocks created spherical micelles stabilized by PGLBT motifs, and the transition behavior diminished by decreasing the PSPE ratio. No particular change was found in the diblocks that had an identical AB ratio. This trend reappeared in the other set whose entire molecular weight approximately doubled, and each transition point was not recognizably impacted by the total molecular weight. For triblocks, the PSPE double ends provided a higher probability of interchain attractions and resulted in a more turbid solution at higher temperatures, compared to the diblocks which had similar block ratios and molecular weights. The intermediates assumed as network-like soft aggregates eventually rearranged to monodisperse flowerlike micelles. It is expected that the method for obtaining well-defined betaine block copolymers, as well as the relationship of the block ratio and the chain conformation to the temperature-responsive behavior, will be helpful for designing betaine-based polymeric applications.

Dual stimuli-responsive polymeric nanoparticles combining soluplus and chitosan for enhanced breast cancer targeting.

A dual stimuli-responsive nanocarrier was developed from smart biocompatible chitosan and soluplus graft copolymers. The copolymerization was investigated by differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA), and Fourier transform infrared (FTIR). The optimized chitosan-soluplus nanoparticles (CS-SP NPs) were further used for the encapsulation of a poorly water-soluble anticancer drug. Tamoxifen citrate (TC) was used as the model drug and it was loaded in CS-SP NPs. TC CS-SP NPs were characterized in terms of particle size, zeta potential, polydispersity, morphology, encapsulation efficiency, and physical stability. The nanoparticles showed homogenous spherical features with a size around 94 nm, a slightly positive zeta potential, and an encapsulation efficiency around 96.66%. Dynamic light scattering (DLS), in vitro drug release, and cytotoxicity confirmed that the created nano-system is smart and exhibits pH and temperature-responsive behavior. In vitro cellular uptake was evaluated by flow cytometry and confocal microscopy. The nanoparticles revealed a triggered increase in size upon reaching the lower critical solution temperature of SP, with 70% of drug release at acidic pH and 40 °C within the first hour and a 3.5-fold increase in cytotoxicity against MCF7 cells incubated at 40 °C. The cellular uptake study manifested that the prepared nanoparticles succeeded in delivering drug molecules to MCF7 and MDA-MB-231 cells. In summary, the distinctive characteristics provided by these novel CS-SP NPs result in a promising nano-platform for effective drug delivery in cancer treatment.

A highly tuneable inverse emulsion polymerization for the synthesis of stimuli-responsive nanoparticles for biomedical applications.

Polymeric nanomaterials have seen widespread use in biomedical applications as they are highly tuneable to achieve the desired stimuli-responsiveness, targeting, biocompatibility, and degradation needed for fields such as drug delivery and biosensing. However, adjustments to composition and the introduction of new monomers often necessitate reoptimization of the polymer synthesis to achieve the target parameters. In this study, we explored the use of inverse emulsion polymerization to prepare a library of polymeric nanoparticles with variations in pH and temperature response and examined the impact of overall batch volume and the volume of the aqueous phase on nanoparticle size and composition. We were able to prepare copolymeric nanoparticles using three different nonionic and three different anionic comonomers. Varying the non-ionizable comonomers, acrylamide (AAm), 2-hydroxyethyl methacrylate, and N-isopropylacrylamide (NIPAM), was found to alter the mass percentage of methacrylic acid (MAA) incorporated (from 26.7 ± 3.5 to 45.8 ± 1.8 mass%), the critical swelling pH (from 5.687 ± 0.194 to 6.637 ± 0.318), and the volume swelling ratio (from 1.389 ± 0.064 to 2.148 ± 0.037). Additionally, the use of NIPAM was found to allow for temperature-responsive behavior. Varying the ionizable comonomers, MAA, itaconic acid, and 2-acrylamido-2-methylpropane sulfonic acid (AMPSA), was found to significantly alter the critical swelling pH and, in the case of AMPSA, remove the pH-responsive behavior entirely. Finally, we found that for the base P(AAm-co-MAA) formulation, the pH-responsive swelling behavior was independent of the scale of the reaction; however, variations in the aqueous volume relative to the volume of the continuous phase significantly affected both the nanoparticle size and the critical swelling pH.

Temperature response behavior of poly(1-vinyl-3-methylimidazole dimethyl phosphate-co-N-isopropylacrylamide) in aqueous and ester solutions driven by hydrogen bonding

A series of poly(1-vinyl-3-methylimidazole dimethyl phosphate-co-N-isopropylacrylamide) oligomers was synthesized by reversible addition-fragmentation chain transfer polymerization. The co-oligomers exhibited a pH-tunable lower critical solution temperature (LCST) phase transition in aqueous solutions. By changing the pH of the aqueous solution (HCI), the hydrogen bonding between the internal molecules of the co-oligomers and water molecules was weakened, which effectively reduced the cloud-point temperature. Poly(1-vinyl-3-methylimidazole dimethyl phosphate-co-N-isopropylacrylamide) oligomers exhibit an upper critical solution temperature (UCST) type of phase transition in an ester solution, which is associated with the formation and breaking of hydrogen bonds within the co-oligomers molecules. FT-IR analysis revealed the effect of temperature on hydrogen bonding between the functional groups. Energy decomposition, Electrostatic Potential (ESP), Atoms-in-Molecules (AIM), and Interaction region indicator (IRI) analyses demonstrated the presence of hydrogen bond donors N–H and imidazole ring C–H, and hydrogen bond acceptors C = O and P = O in the co-oligomers. The sites of hydrogen bonding between the co-oligomers and the solvent molecules as well as intermolecular forces were found to be the main factors contributing to the LCST/UCST-type phase transition.

Development of a Temperature-Responsive Hydrogel Incorporating PVA into NIPAAm for Controllable Drug Release in Skin Regeneration.

Melanoma, a highly malignant and aggressive form of skin cancer, poses a significant global health threat, with limited treatment options and potential side effects. In this study, we developed a temperature-responsive hydrogel for skin regeneration with a controllable drug release. The hydrogel was fabricated using an interpenetrating polymer network (IPN) of N-isopropylacrylamide (NIPAAm) and poly(vinyl alcohol) (PVA). PVA was chosen for its adhesive properties, biocompatibility, and ability to address hydrophobicity issues associated with NIPAAm. The hydrogel was loaded with doxorubicin (DOX), an anticancer drug, for the treatment of melanoma. The NIPAAm-PVA (N-P) hydrogel demonstrated temperature-responsive behavior with a lower critical solution temperature (LCST) around 34 °C. The addition of PVA led to increased porosity and faster drug release. In vitro biocompatibility tests showed nontoxicity and supported cell proliferation. The N-P hydrogel exhibited effective anticancer effects on melanoma cells due to its rapid drug release behavior. This N-P hydrogel system shows great promise for controlled drug delivery and potential applications in skin regeneration and cancer treatment. Further research, including in vivo studies, will be essential to advance this hydrogel system toward clinical translation and impactful advancements in regenerative medicine and cancer therapeutics.

Multifunctional hollow silica carriers with spiny structure for enhanced foliar adhesion and triple-responsive pesticide delivery

Intelligent responsive pesticide formulations hold great promise for enhancing foliage retention and effective utilization. Herein, hollow silica (S-HS) nanocarriers with spiny structure were constructed for pesticide delivery. The S-HS nanocarriers presented homogeneous spiny spheres with an average size of 220 nm. This spiny structure can achieve effective retention on foliage by the “hanger-hat” topology effect. For constructing the responsive layer, the S-HS nanocarriers were further functionalized with surface vinyl groups. After loading imidacloprid (IMI), the temperature sensitive poly N-isopropylacrylamide (pNIPAm) and tannic acid–Fe complexes (TA-Fe) were introduced to encapsulate pesticides (IMI@S-HS-pNT). The TA-Fe complex layer served as a wall material and photothermal agent. The S-HS-pNT carriers achieved a loading capacity for IMI (26.6 %), high photothermal conversion effect (η = 36.1 %), and good biocompatibility. Except for excellent photostability and foliar adhesion property, the IMI@S-HS-pNT exhibited pH, temperature and near infrared (NIR) responsive release behavior. Moreover, the S-HS nanocarriers could be effectively transported to various parts of tobacco plants under the root immerse or foliar spray. The IMI@S-HS-pNT showed the high control efficacy against Plutella xylostella. Overall, this work provides insight into improving the efficiency of utilization and prolonging pesticide retention on plant leaves.

Boron-doped copper phenylphosphate as temperature-response nanosheets to fabricate high fire-safety polycarbonate nanocomposites

The application of polymer materials has provided the convenience and also bring fire risk and hazard due to intrinsic flammable property of polymers. Here we demonstrate a novel strategy using boron-doped copper phenylphosphate (BCuPP) nanosheets with temperature-response characteristics as only flame retardant for creating high fire-safety polycarbonate (PC) nanocomposites with excellent comprehensive performances. PC/BCuPP nanocomposites presents a good mechanical performance at room temperature due to the strong interfacial interaction between PC matrix and BCuPP nanosheets. Furthermore, BCuPP exhibits unique temperature-response behavior driven by fire, where fully molten boron oxide flows freely, followed by in-situ formed BPO4 to repair the defects to form a complete and continuous protective layer. So the temperature-response behavior endows PC/BCuPP nanocomposites excellent fire-safety performance with dramatical decrease in both heat release rate and total smoke production. This study offers a novel route only incorporating nanoparticles as flame retardant to create high fire-safety polymer nanocomposites.

Zwitterion-Modified Nanogel Responding to Temperature and Ionic Strength: A Dissipative Particle Dynamics Simulation.

The self-assembly and stimuli-responsive properties of nanogel poly(n-isopropylacrylamide) (p(NIPAm)) and zwitterion-modified nanogel poly(n-isopropylacrylamide-co-sulfobetainemethacrylate) (p(NIPAm-co-SBMA)) were explored by dissipative particle dynamics simulations. Simulation results reveal that for both types of nanogel, it is beneficial to form spherical nanogels at polymer concentrations of 5-10%. When the chain length (L) elongates from 10 to 40, the sizes of the nanogels enlarge. As for the p(NIPAm) nanogel, it shows thermoresponsiveness; when it switches to the hydrophilic state, the nanogel swells, and vice versa. The zwitterion-modified nanogel p(NIPAm-co-SBMA) possesses thermoresponsiveness and ionic strength responsiveness concurrently. At 293 K, both hydrophilic p(NIPAm) and superhydrophilic polysulfobetaine methacrylate (pSBMA) could appear on the outer surface of the nanogel; however, at 318 K, superhydrophilic pSBMA is on the outer surface to cover the hydrophobic p(NIPAm) core. As the temperature rises, the nanogel shrinks and remains antifouling all through. The salt-responsive property can be reflected by the nanogel size; the volumes of the nanogels in saline systems are larger than those in salt-free systems as the ionic condition inhibits the shrinkage of the zwitterionic pSBMA. This work exhibits the temperature-responsive and salt-responsive behavior of zwitterion-modified-pNIPAm nanogels at the molecular level and provides guidance in antifouling nanogel design.