Sol State Research Articles

Hypothermic Stem Cell Storage Using a Polypeptide Thermogel.

We report a polypeptide-based thermogel as a new tool for hypothermic storage of stem cells at ambient temperature (25 °C). Stem cells were suspended in the sol state (10 °C) of an aqueous poly(ethylene glycol)-poly(l-alanine) (PEG-PA) solution (4.0 wt %) in phosphate-buffered saline (PBS), which turned into a stem cell-incorporated gel by a heat-induced sol-to-gel transition. The cell harvesting procedure from the thermogels was simply performed through a gel-to-sol transition by diluting and cooling the system. More than 99% of stem cells died in PBS and Pluronic F127 thermogel (control thermogel) when the cells were stored at 25 °C for 7 days. The cell recovery rate from the PEG-PA thermogel (64%) was significantly greater than that from the commercially available HypoThermosol FRS preservation solution (HTS) (26%). Additionally, the surviving stem cells from the PEG-PA thermogel were healthier than those from HTS in terms of (1) expression of stemness biomarkers (NANOG, OCT4, and SOX2), (2) proliferation rate, and (3) differentiation potentials into osteogenic, chondrogenic, and adipogenic lineages. Membrane stabilization was suggested as a cell protection mechanism in the cytocompatible PEG-PA thermogel. The PEG-PA thermogel provides a convenient cytocompatible way for the storage and recovery of cells and thus is a promising tool for the transportation and short-term banking of cells.

Injectable thermosensitive lipo-hydrogels loaded with ropivacaine for prolonging local anesthesia

Reducing post-surgical pain can promote recovery of mobility, improve patient satisfaction, and reduce the risk of chronic pain syndrome. When managing post-surgical pain, single-injection local anesthesia is more convenient and involves lower risk to the patient than multi-injection regimes, but the effects are not long-lasting. Here we developed a system that can prolong local anesthesia after a single injection. In this system, ropivacaine (Ro) is encapsulated into liposomes, which are then loaded into Poloxamer 407-based thermosensitive hydrogels. The Ro-loaded liposome-in-gel system (Ro-Lip-Gel) is in a sol state before injection, and immediately after subcutaneous injection, it forms a gel in situ. We show through in vitro release and in vivo pharmacokinetics studies that this gel acts as a drug release depot. In rats, the initial burst release of Ro was smaller from Ro-Lip-Gel than from Ro solution or Ro-Gel, and Ro-Lip-Gel caused nerve blockade lasting four times longer than Ro solution. Ro-Lip-Gel degraded in vivo and showed good biocompatibility. Our results suggest that a liposome-in-gel system can show small initial burst release, long-term nerve blockade and good biocompatibility in vitro and in vivo. Therefore, such a system may be useful for sustained local anesthesia without systemic toxicity.

Physical properties and conformational changes of shrimp surimi from Litopenaeus vannamei during cold gelation

Variations in the cold gelation of shrimp surimi at low temperatures significantly affect their gel properties and secondary processing. In this study, the physical properties and protein conformation of shrimp surimi at 4 °C storage were investigated for fresh shrimp (F0) and shrimp frozen for 4/8 months (F4/F8). Gel hardness and frequency tests indicated that F0 maintained a sol state, whereas F4 and F8 exhibited elastic gel characteristics, and a higher degree of crosslinking occurred in F8 during storage. Gel electrophoresis revealed that the myosin heavy chain underwent polymerization in F4 and F8 during cold storage. The Raman spectra showed that F4 and F8 exhibited lower α-helix and higher β-sheet contents after storage. The intensity of C–H bending peaks and the ratio of tyrosine doublet bands also decreased significantly in F4 and F8. The changes in the secondary and tertiary structures in F8 were more notable than those in F4. Scanning electron microscopy confirmed the formation of the most compact gel network in F8. These results helped clarify the gelation process of shrimp surimi prepared from fresh and frozen states at low temperatures and contributed to regulate the gelation properties of shrimp surimi products.

Temperature and pH-responsive in situ hydrogels of gelatin derivatives to prevent the reoccurrence of brain tumor

Glioblastoma multiforme (GBM) is a grade IV malignant brain tumor with a median survival time of approximately 12–16 months. Because of its highly aggressive and heterogeneous nature it is very difficult to remove by surgical resection. Herein we have reported dual stimuli-responsive and biodegradable in situ hydrogels of oligosulfamethazine-grafted gelatin and loaded with anticancer drug paclitaxel (PTX) for preventing the progress of Glioblastoma. The oligosulfamethazine (OSM) introduced to the gelatin backbone for the formation of definite and stable in situ hydrogel. The hydrogels transformed from a sol to a gel state upon changes in stimuli. pH and temperature and retained a distinct shape after subcutaneous administration in BALB/c mice. The viscosity of the sol state hydrogels was tuned by varying the feed molar ratio between gelatin and OSM. The porosity of the hydrogels was confirmed to be lower in higher degree OSM by SEM. Sustained release of PTX from hydrogels in physiological environments (pH 7.4) was further retarded up to 63% in 9th days in tumor environments (pH 6.5). While the empty hydrogels were non-toxic in cultured cells, the hydrogels loaded with PTX showed antitumor efficacy in orthotopic-GBM xenograft mice. Collectively, the gelatin-OSM formed porous hydrogels and released the cargo in a sustained manner in tumor environments efficiently suppressing the progress of GBM. Thus, gelatin-OSM hydrogels are a potential candidate for the direct delivery of therapeutics to the local areas in brain diseases.

Molecular interaction of poly (acrylamide‐co‐2‐acrylamido‐dodecyl sulfonate) with dual responsiveness and application in oily emulsion wastewater

AbstractStimuli‐sensitive polymers are a class of macromolecular system with “intelligent” behavior. Herein, a copolymer of poly (acrylamide‐co‐2‐acrylamido‐dodecyl sulfonate), which has salt‐sensitive and thermosensitive properties, is synthesized via precipitation polymerization. Its aqueous solution exhibits a clear sol state, while a gel is obtained via salt‐induction by addition a certain amount of NaCl. More interestingly, the gel can transform into clear sol again upon heating, which exhibits a phase transition of upper critical solution temperature in NaCl solution. The dual responsive behaviors of copolymer solutions are studied via rheological measurements. Then fluorescence spectrum, zeta potential test, and dynamic light scattering are employed to investigate molecular interaction in aqueous solution under varying conditions. It is found that dual responsive behaviors are caused by electrostatic interaction and hydrophobic association. At last, oily emulsion wastewater treatment indicates that this polymer shows characteristics of “smart flocculant” and has potential application prospect.

Synthesize of 3D-conductive supramolecular gel and derived N-doped Fe–C as high-performance lithium-ion battery anodes

In this work, 3D-conductive supramolecular gel and derivates were synthesized and the performance of lithium storage were explored. In sol or gel state of iron-based metal-organic gel (Fe-MOG), the redox reaction of Fe3+ will generate free radicals which can catalyze the polymerization of pyrrole. Meanwhile, the conductive polymer could be more uniformly and closely coated on the internal structure of Fe-MOG. Systematic electrochemical analysis demonstrated that 3D-conductive supramolecular gel anode performed a stable reversible specific capacity of 1304.9 mAh g−1 at the current density of 0.1 A g−1, and outstanding cycle performance with high reversible specific capacity of 824.5 mAh g−1 at the current density of 0.4 A g−1 after 300 cycles and 422.3 mAh g−1 at the current density of 2 A g−1 after 100 cycles. At the same time, supramolecular gel-derived N-doped Fe–C could also show excellent performance of lithium storage as a novel carbon material, demonstrating that 3D-conductive supramolecular gel has a broad application prospect in the field of lithium-ion batteries (LIBs).

On the inverse quenching technique applied to gelatin solutions

Gelatin gels are known to be nonequilibrium systems, because of the continuous growth and rearrangements of physical junctions, even in the solidlike state. Establishing a relationship between the relative degree of cross-linking and macroscopic elasticity would be crucial in understanding, modeling, and predicting the transformation processes of gelatin solutions. Performing rheological experiments on a distinct gel structure, with a definite number of cross-links, is, however, a challenging task. In isothermal conditions, indeed, the density of physical cross-links changes indefinitely, and network evolution cannot be arrested. Inspired by the inverse quenching technique applied in the past to semicrystalline polymers, we here apply an unusual thermal history to an aqueous solution of gelatin in the semiconcentrated regime (6.67%w pig-skin gelatin), in order to freeze the system in a metastable condition for a time sufficiently long to perform a rheological characterization. The solution, initially kept in the sol state at 60°C, is rapidly cooled below gelation temperature, and isothermal gelation is started at 10°C. After soaking at this low temperature for a given time, the sample is rapidly heated (inverse quenching) up to a value in the range 24–29 °C, where kinetics is monitored. If the waiting time at low temperature and the inverse quenching temperature are suitably chosen, sample elasticity will remain stationary for a relatively large time window, and rheological experiments can then be reliably performed.

Injectable polymeric nanoparticle hydrogel system for long-term anti-inflammatory effect to treat osteoarthritis

Treatment of osteoarthritis (OA) by administration of corticosteroids is a commonly used method in clinics using anti-inflammatory medicine. Oral administration or intra-articular injection of corticosteroids can reduce the pain and progress of cartilage degeneration, but they are usually insufficient to show local and long-term anti-inflammatory effects because of their fast clearance in the body. In this study, we suggest an injectable anti-OA drug depot system for sustained drug release that provides long-term effective therapeutic advantages. Amphiphilic poly(organophosphazene), which has temperature-dependent nanoparticle forming and sol-gel transition behaviors when dissolved in aqueous solution, was synthesized for triamcinolone acetonide (TCA) delivery. Because hydrophobic parts of the polymer can interact with hydrophobic parts of the TCA, the TCA was encapsulated into the self-assembled polymeric nanoparticles. The TCA-encapsulated polymeric nanoparticles (TePNs) were well dispersed in an aqueous solution below room temperature so that they can be easily injected as a sol state into an intra-articular region. However, the TePNs solution transforms immediately to a viscose 3D hydrogel like a synovial fluid in the intra-articular region via the conducted body temperature. An in vitro TCA release study showed sustained TCA release for six weeks. One-time injection of the TePN hydrogel system in an early stage of OA-induced rat model showed a great inhibition effect against further OA progression. The OA-induced knees completely recovered as a healthy cartilage without any abnormal symptoms.

The study of rheological properties and microstructure of carboxylated nanocellulose as influenced by level of carboxylation

In this work, carboxylated nanocellulose had been prepared by using TEMPO-periodate oxidized reaction, in which the level of carboxylation was controlled by adjusting sodium hypochlorite (NaClO) concentration. The effects of the level of carboxylation on the rheological behavior and microstructure for the carboxylated nanocellulose dispersion had been investigated. It indicated that the nanocellulose dispersion exhibited sol state with low storage (G′) and loss (G″) modulus when NaClO concentration controlled to 2 mmol/g. But nanocellulose dispersion presented a form of gel at high NaClO concentration (6–12 mmol/g) and a critical state (similar values of G′ and G″) was obtained with the NaClO concentration of 4 mmol/g. In addition, both the G′ and G″ of nanocellulose dispersion were increased and then decreased with the increase of NaClO concentration. The highest modulus obtained when NaClO concentration controlled to 8 mmol/g, and a high fractal dimension (Df) was also obtained at this concentration, indicating a compact network structure. The large amplitude oscillation shear (LAOS) suggested that nanocellulose dispersion exhibited Ⅰ behavior (strain thinning) but had a trend of III behavior (weak strain overshoot). The Fourier transform rheology, Chebyshev coefficient, and Lissajous curves were used to analyze the nonlinear behavior, implying a correlation between the nonlinear behavior and the network structure of the nanocellulose dispersion. This work would provide some guidance for regulating the properties of nanocellulose dispersion.

Preparation and Characterization of Oleanolic Acid-Based Low-Molecular-Weight Supramolecular Hydrogels Induced by Heating.

The natural-product-based low-molecular-weight supramolecular hydrogels (LMWSHs) induced by heating are rarely reported. In this work, a simple salt of oleanolic acid (OA) and choline ([choline][OA]) was used as the natural product hydrogelator (NPHG) to form LMWSHs. Unlike common sol-gel transitions, the OA-based LMWSH displayed a unique property with which the system could undergo a phase transition from the sol state to the gel state upon heating. Moreover, the phase separation was observed in sol and gel states when the temperature was elevated with nonreversible transparent-turbid transitions. LMWSHs showed good stability and injectability and the potential to be a drug delivery vehicle for sustained release of drugs. In this regard, this work provided a facile approach to designing an OA-based NPHG for preparing heat-induced LMWSHs.

Injectable Temperature/Glucose Dual-Responsive Hydrogels for Controlled Release of Insulin

Self-regulating insulin controlled-release systems have gained more attention due to their advantages of timely response to blood glucose change and avoiding side effects caused by the high-frequency injection. In this paper, the temperature-responsive monomer N-isopropylacrylamide (NIPAM) and glucose-responsive monomer 3-acrylamidophenylboronic acid (AAPBA) are copolymerized and then grafted with alginate to prepare temperature/glucose dual-responsive copolymers alginate-g-P(NIPAM-co-AAPBA) (Alg-g-PNA). The temperature and glucose responsiveness under different conditions, rheological characteristics, glucose-mediated insulin release, and biotoxicity of the Alg-g-PNA copolymers are studied. The results show that the copolymer solution is in the sol state at 10 °C and insulin can be dispersed uniformly, while it turns into the gel state when the temperature rises to physiological 37 °C for in situ delivery of insulin. Due to the sensitivity to blood glucose levels, the hydrogels can quickly respond to the increase in blood glucose and undergo the gel-to-sol transition and release insulin to reduce blood glucose when the environmental blood glucose rises. Moreover, the hydrogels have good sol–gel transition reversibility in response to changes between normoglycemic and hyperglycemic levels. The cell cytotoxicity results show that the hydrogels have good biocompatibility to be a safe carrier for insulin delivery. The proposed injectable temperature/glucose dual-responsive hydrogels in this study provide a novel type of self-regulating insulin delivery systems for diabetes therapy.

Bio-inspired Incrustation Interfacial Polymerization of Dopamine and Cross-linking with Gelatin toward Robust, Biodegradable Three-Dimensional Hydrogels.

In nature, laccase enzymatically catalyzes the reaction of phenolic compounds with oxygen to produce hardened surfaces known as cuticles on insects and plants. Inspired by this natural process, the present work investigated a robust, biodegradable hydrogel synthesized from dopamine and gelatin. This gel is obtained by the oxidation of dopamine dissolved in water, after which the resulting quinone compound automatically undergoes self-polymerization. The oxidized dopamine subsequently undergoes Schiff base and Michael addition reactions with gelatin, such that the exposed gelatin surface cross-links to generate a continuous hardened hydrogel film. Because gelatin transitions between sol and gel states with changes in temperature, two- and three-dimensional structures could be obtained from the gel state. This bio-inspired interfacial cross-linking reaction provides a simple means of forming complex morphologies and represents a promising technique for bio-applications.

Formula optimization of thermosensitive biological sol–gel carrier for EOR surfactants by rheological investigation

Adsorption loss of surfactants by rock formations reduces surfactant efficiency and increases cost. We propose a new approach to solve this problem. Xanthan gum/locust bean gum (XLB) and xanthan gum/konjac glucomannan (XKG) were chosen as surfactant carriers. Both XLB and XKG are thermosensitive; they are in a gel state at low temperature and sol state at high temperature. When the temperature near an injection well is low, gelled carriers can shield surfactant charge and reduce adsorption loss of surfactants by the formation. A high temperature deep in the reservoir transforms the carriers into a sol state to release the surfactants. In this way, the transport distance of the surfactants is increased, which enables the surfactants to contact more crude oil. The effects of ratio, pH, and salinity on the rheological properties of the XLB and XKG systems were evaluated to optimize the formulation and define the sol–gel transition temperature (Tsol/gel). The storage modulus and loss modulus of the system was affected by the ratio of rigid glue (XG) and flexible glue (LBG and KGM). Adding acid or base weakened the shear modulus, CaCl2 and NaCl had little effect on the shear modulus, and KCl significantly increased this property. The shear modulus of these two systems was greatest when the two biogels were mixed in equal proportion, the pH was not adjusted, and 3% KCl was added. Environmental scanning electron microscopy images revealed that KCl transformed the loose porous crosslinked structure into a dense lamellar structure. Sodium lauryl sulfate (SDS) and hexadecyl dimethylamine betaine had little influence on the shear modulus of the system, while cetyl trimethyl ammonium bromide prevented the systems from gelatinizing. The zeta potential and surface tension of XLG (XLB with 2% KCl) and XKG (XKG with 2% KCl) with 3% SDS were measured. The absolute values of their zeta potentials in the gel state were smaller than those in the sol state, which indicates that XLG and XKG effectively shielded surfactant charge. The surface tension decreased with increasing temperature. When the temperature was higher than the Tsol/gel, the gel melted completely and the surface tension was almost unchanged. This indicates that the surfactants were released slowly by the carriers before melting was complete. Both XLG and XKG proved to be efficient carriers for surfactants that are used for oil displacement.

Research progress on transient hydrogels

Hydrogels are a kind of soft and wet materials, which have three-dimensional network structures formed by polymers or small molecules in water through self-assembly or chemical cross-linking. Hydrogels can be divided into two categories of chemical and physical hydrogels according to the ways of hydrogel formation. The chemical hydrogels containing covalent bonds have high chemical resistance and thermodynamic stability. However, they are usually nondegradable and unrecyclable due to the irreversibility of covalent bonds, which limits their practical application. By contrast, various stimuli-responsive hydrogels based on supramolecular interactions or dynamic covalent bonds have become the research focus in recent years. These studies expand the application of hydrogels in drug delivery, biosensing, shape memory, etc. However, the classical responsiveness of the hydrogels is relatively passive, which always requires an external stimulus to induce the assembly or disassembly of the hydrogel networks and lacks the ability of self-regulation. Self-regulating systems are very common in living organisms, such as the reversible formation of intracellular actin. The non-equilibrium dynamic processes generate transient assemblies, which inspires the researchers to design artificial non-equilibrium systems. In 2010, a transient supramolecular hydrogel mediated by chemical fuels was presented for the first time. In the following decade, the researchers have been exploring how to mimic the living systems by simply mixing chemical reagents to build artificial non-equilibrium systems. The emergence of transient hydrogels is a significant breakthrough in the field of smart hydrogel materials. In the system, a switch that can induce sol-gel transitions autonomously is set up, which endows the soft materials with autonomy or adaptability. The scientists have realized the versatile regulation of the structure, function and lifespan of the hydrogels by imitating the complex living systems and combining the existing biocatalytic and/or chemical reactions. For example, for injectable biomaterials, the precise control on the lifetime of the transient hydrogels contributes to the timed release of drugs. Moreover, the transient hydrogels can also be used as temporary seals or adhesives for biomedical applications. At the same time, the remote-controlled time programmability is of great significance for the in situ study of self-assembly in closed systems. Although the research on transient hydrogels is still in its infancy, the advanced characteristics of the transient hydrogels, as well as the spatiotemporal regulation mode for the precise control of material properties, suggest that the transient hydrogels will be an important class of intelligent soft materials useful in many fields such as drug delivery, data encryption, material repairing and reprocessing in the future. In short, the transient hydrogel systems regulated by the chemical reaction networks are one of the important results inspired from the dissipative assembly in living systems. They significantly broaden the application range of hydrogels. In general, the current research in the field of transient hydrogels mainly focuses on the expansion of transient hydrogel systems and the design of transition modes, which requires a deeper understanding of the hydrogel formation mechanisms. Therefore, it is necessary to make a systematic summary for this rapidly developing field at this point. In this review, we give a clear definition of transient hydrogels: transient hydrogels refer to water-based temporary gels formed in non-equilibrium states, which can spontaneously convert to sol states mediated by internal reactions. According to the difference in hydrogel formation mechanisms, the classification of hydrogels is presented. Furthermore, the existing transient hydrogel systems are reviewed in detail. The application and limitation of transient hydrogels are summarized, and the future development direction is discussed and prospected lastly in this review.

Wide and Tunable Bandgap MAPbBr3−xClx Hybrid Perovskites with Enhanced Phase Stability: In Situ Investigation and Photovoltaic Devices

The current understanding of the crystallization, morphology evolution, and phase stability of wide‐bandgap hybrid perovskite thin films is very limited, as much of the community's focus is on lower bandgap systems. Herein, the crystallization behavior and film formation of a wide and tunable bandgap MAPbBr3−xClx system are investigated, and its formation and phase stability are contrasted to the classical MAPbI3−xBrx case. A multiprobe in situ characterization approach consisting of synchrotron‐based grazing incidence wide‐angle X‐ray scattering and laboratory‐based time‐resolved UV–Vis absorbance measurements is utilized to show that all wide‐bandgap perovskite compositions of MAPbBr3−xClx studied (0 < x < 3) crystallize the same way: the perovskite phase forms directly from the colloidal sol state and forms a solid film in the cubic structure. This results in significantly improved alloying and phase stability of these compounds compared with MAPbI3−xBrx systems. The phase transformation pathway is direct and excludes solvated phases, in contrast to methylammonium lead iodide (MAPbI3). The films benefit from antisolvent dripping to overcome the formation of discontinuous layers and enable device integration. Pin‐hole‐free MAPbBr3−xClx hybrid perovskite thin films with a tunable bandgap are, thus, integrated into working single‐junction solar cell devices and achieve a tunable open‐circuit voltage as high as 1.6 V.

Phenomenological model of viscoelasticity for systems undergoing sol–gel transition

A material undergoing sol–gel transition evolves from the pre-gel (sol) state to the post-gel state through the critical gel state. It is well-known that critical gels exhibit power-law rheology. The faster decay of the relaxation modulus in the pre-gel state can be empirically described by modifying this power-law decay with a stretched exponential factor. A phenomenological analytical expression for the relaxation modulus in the post-gel state is proposed by invoking the symmetry associated with the evolution of the relaxation time on either side of the critical gel state and by accounting for natural constraints. This expression, which depends on the extent of cross-linking, can be suitably transformed to obtain analytical expressions for the dynamic moduli and the continuous relaxation time spectrum. Thus, the proposed model facilitates a comprehensive description of viscoelastic evolution from the pre-gel to the post-gel states. It is validated by carrying out experiments on a model colloidal gel-forming system and by considering other diverse gel-forming systems studied in the literature. After calibrating the parameters of the phenomenological model, it is found to be in excellent agreement with experimental data. Such a well-calibrated phenomenological model can be used to determine any linear viscoelastic response over a wide range of frequencies and extents of cross-linking encompassing the entire sol–gel transition.

Investigation of the effect of trisodium-citrate on blood coagulation by viscometric approach

AbstractBlood coagulation is a process, which is initiated by certain physico-chemical effects. This process results in a change in the blood from the sol state, that is well suited for further processing, to gel state. 13 blood clotting factors take part in the cascade system of blood coagulation. Trisodium-citrate affects factor IV, the calcium, and prevents the change in blood texture. The effect of different concentrations of trisodium-citrate (0, 0.48, 2.4, 4.8, 9.6, 14.4, 19.2, 24 w/w%) on the texture of blood is investigated. Porcine blood was collected in 20 cm3 test tubes in a slaughterhouse directly before trisodium-citrate addition and was stored for one day under refrigerated conditions. The samples without trisodium-citrate coagulated and the samples with high trisodium-citrate (4–5 g) became solid as well because of the protein salting-out. The viscosity of successfully treated samples and the shear stress were measured with a rotational viscometer (Physica MCR 51, Anton-Paar) with concentric cylinders and Couette type method. The flow behavior of all samples could be described by the Herschel-Bulkley model. The yield point, the consistency index and the power of law index, which are determined by the equation of the model, showed that the samples with lower trisodium-citrate content coagulated “better” and the sample with high trisodium-citrate were most similar to Newtonian fluid. The results are trend-likes, but significant differences may be expected in the case of higher sample amount. The yield point of the sample, which contained 14.4 w/w% trisodium-citrate, was by 37.3% less than the sample containing 0.48% trisodium-citrate, and the consistency index of the sample with 3 g trisodium-citrate was by 20.5% higher than that of the sample with 0.48% trisodium-citrate. Thanks to these results a cheaper concentration and drying of porcine blood and blood fractions are available because no surplus water is added to the blood.

Thermosensitive -hydrogel-coated titania nanotubes with controlled drug release and immunoregulatory characteristics for orthopedic applications

Although Ti is widely used in orthopedic implants, its bio-inert characteristics and poor antibacterial activity may result in implant failure. To counter this problem, in this study, we loaded simvastatin, a bioactive compound that promotes osteogenesis, in TiO2 nanotubes and a thermosensitive chitosan-glycerin-hydroxypropyl methyl cellulose hydrogel (CGHH) was then layered on top of these nanotubes. At normal human-body temperature (37 °C), CGHH was present in a sol state, thus facilitating the controlled release of simvastatin to enhance differentiation in MC3T3-E1 osteoblasts. In vitro cell-culture studies suggested that CGHH in a gel state would induce macrophage polarization to the pro-inflammatory M1 phenotype. In vitro testing against Escherichia coli and Staphylococcus aureus indicated no antibacterial activity in CGHH in both sol and gel states. However, the results of subcutaneous infection animal models suggested that CGHH showed excellent in vivo antibacterial activity, which can be explained by the fact at high temperatures induced by an infection, CGHH transitioned into a gel state and released large amounts of glycerin. Such a high glycerin dosage induced an acute inflammatory reaction and antibacterial activity. Thus, due to their enhanced osteogenesis capacity at normal body temperature and antibacterial characteristics in the presence of infection, the newly designed simvastatin-loaded CGHH-encapsulated TiO2 nanotubes are promising materials for application in orthopedic implants.

Controllable Self-Assembly of SERS Hotspots in Liquid Environment.

Controllable synthesis of novel metal nanoparticles and effective capture of hotspots are of great significance for SERS (surface-enhanced Raman spectroscopy) detection. Therefore, in this paper, a green controllable synthesis method of gold nanoparticle was achieved via epigallocatechin gallate reduction. Different morphologies of gold nanoparticles were synthesized just by changing the solution pH values, and the growth kinetics of AuNPs (gold nanoparticles) were systematically studied. The synthetic AuNPs were put in a droplet to study dynamic variations of self-assembly SERS hotspots from the liquid sol state to the solid dry state. The addition of halogen ions in the droplet can controllably regulate the self-assembly three-dimensional hotspot model of gold nanoparticles in the evaporation process of a droplet, during which the most enhancement effect can be easily captured. The dynamically changing images of nanoparticles in the process were graphically described based on the internal interaction forces of a droplet. Two stronger areas in the changes of SERS intensity were achieved with a high concentration of halogen ions, while only one maximum intensity area was obtained with a low concentration of halogen ions added. This method can effectively avoid complex and unpredictable microenvironments of SERS substrates in the liquid drop, further improving the reproducibility of SERS detection as well as broadening it to biological applications.

Semi-convertible Hydrogel Enabled Photoresponsive Lubrication

Summary A semi-convertible hydrogel with reversible photoresponsive supramolecular lubricating ability is demonstrated by integrating a responsive supramolecular system of α-cyclodextrins/polyethylene glycol (α-CD/PEG) and competitive guest 1-[p-(phenylazo)benzyl]pyridinium bromide (AzoPB) within a poly(vinyl alcohol) (PVA) and polyacrylamide (PAAm) framework. The competitive host-guest interaction between α-CD/PEG supramolecular network and AzoPB after UV and visible-light irradiation enables the appearance and disappearance of the sol-state layer on the hydrogel surface while the PVA and PAAm consistently keeps the framework. This semi-convertible process realizes the reversible photoresponsive lubricating ability and variable toughness. We envision that this finding will offer a possible way for fabricating novel smart devices far beyond lubrication, leading to an emerging branch of interdisciplinary materials science that integrates supramolecular chemistry, hydrogel, and surface science.