Convex Dual Theory Analysis of Two-Layer Convolutional Neural Networks With Soft-Thresholding.

Soft-thresholding has been widely used in neural networks. Its basic network structure is a two-layer convolution neural network with soft-thresholding. Due to the network's nature of nonlinear and nonconvex, the training process heavily depends on an appropriate initialization of network parameters, resulting in the difficulty of obtaining a globally optimal solution. To address this issue, a convex dual network is designed here. We theoretically analyze the network convexity and prove that the strong duality holds. Extensive results on both simulation and real-world datasets show that strong duality holds, the dual network does not depend on initialization and optimizer, and enables faster convergence than the state-of-the-art two-layer network. This work provides a new way to convexify soft-thresholding neural networks. Furthermore, the convex dual network model of a deep soft-thresholding network with a parallel structure is deduced.

Evaluation of a biodegradable polyurethane patch for repair of diaphragmatic hernia in a rat model: A pilot study.

INTRODUCTION: Congenital diaphragmatic hernia (CDH) repair is an area of active research. Large defects requiring patches have a hernia recurrence rate of up to 50%. We designed a biodegradable polyurethane (PU)-based elastic patch that matches the mechanical properties of native diaphragm muscle. We compared the PU patch to a non-biodegradable Gore-Tex™ (polytetrafluoroethylene) patch. METHODS: The biodegradable polyurethane was synthesized from polycaprolactone, hexadiisocyanate and putrescine, and then processed into fibrous PU patches by electrospinning. Rats underwent 4 mm diaphragmatic hernia (DH) creation via laparotomy followed by immediate repair with Gore-Tex™ (n = 6) or PU (n = 6) patches. Six rats underwent sham laparotomy without DH creation/repair. Diaphragm function was evaluated by fluoroscopy at 1 and 4 weeks. At 4 weeks, animals underwent gross inspection for recurrence and histologic evaluation for inflammatory reaction to the patch materials. RESULTS: There were no hernia recurrences in either cohort. Gore-Tex™ had limited diaphragm rise compared to sham at 4 weeks (1.3 mm vs 2.9 mm, p = 0.003), but no difference was found between PU and sham (1.7 mm vs 2.9 mm, p = 0.09). There were no differences between PU and Gore-Tex™ at any time point. Both patches formed an inflammatory capsule, with similar thicknesses between cohorts on the abdominal (Gore-Tex™ 0.07 mm vs. PU 0.13 mm, p = 0.39) and thoracic (Gore-Tex™ 0.3 mm vs. PU 0.6 mm, p = 0.09) sides. CONCLUSION: The biodegradable PU patch allowed for similar diaphragmatic excursion compared to control animals. There were similar inflammatory responses to both patches. Further work is needed to evaluate long-term functional outcomes and further optimize the properties of the novel PU patch in vitro and in vivo. LEVEL OF EVIDENCE: Level II, Prospective Comparative Study.

Phytochrome-interacting factors orchestrate hypocotyl adventitious root initiation in Arabidopsis.

Adventitious roots (ARs) are an important type of plant root and display high phenotypic plasticity in response to different environmental stimuli. It is known that photoreceptors inhibit darkness-induced hypocotyl adventitious root (HAR) formation by directly stabilizing Aux/IAA proteins. In this study, we further report that phytochrome-interacting factors (PIFs) plays a central role in HAR initiation by simultaneously inducing the expression of genes involved in auxin biosynthesis, auxin transport and the transcriptional control of root primordium initiation. We found that, on the basis of their activity downstream of phytochrome, PIFs are required for darkness-induced HAR formation. Specifically, PIFs directly bind to the promoters of some genes involved in root formation, including auxin biosynthesis genes YUCCA2 (YUC2) and YUC6, the auxin influx carrier genes AUX1 and LAX3, and the transcription factors WOX5/7 and LBD16/29, to activate their expression. These findings reveal a previously uncharacterized transcriptional regulatory network underlying HAR formation.

Decreasing nitrogen assimilation under drought stress by suppressing DST-mediated activation of Nitrate Reductase 1.2 in rice.

Nitrogen is an essential nutrient for plant growth and development, and plays vital roles in crop yield. Assimilation of nitrogen is thus fine-tuned in response to heterogeneous environments. However, the regulatory mechanism underlying this essential process remains largely unknown. Here, we report that a zinc-finger transcription factor, drought and salt tolerance (DST), controls nitrate assimilation in rice by regulating the expression of OsNR1.2. We found that loss of function of DST results in a significant decrease of nitrogen use efficiency (NUE) in the presence of nitrate. Further study revealed that DST is required for full nitrate reductase activity in rice and directly regulates the expression of OsNR1.2, a gene showing sequence similarity to nitrate reductase. Reverse genetics and biochemistry studies revealed that OsNR1.2 encodes an NADH-dependent nitrate reductase that is required for high NUE of rice. Interestingly, the DST-OsNR1.2 regulatory module is involved in the suppression of nitrate assimilation under drought stress, which contributes to drought tolerance. Considering the negative role of DST in stomata closure, as revealed previously, the positive role of DST in nitrogen assimilation suggests a mechanism coupling nitrogen metabolism and stomata movement. The discovery of this coupling mechanism will aid the engineering of drought-tolerant crops with high NUE in the future.

Efficient Degradation of Iopromide by Using Sulfite Activated with Mackinawite.

Iopromide (IOP), an iodinated X-ray contrast medium (ICM), is identified as a precursor to iodide disinfection byproducts that have high genotoxicity and cytotoxicity to mammals. ICM remains persistent through typical wastewater treatment processes and even through some hydroxyl radical-based advanced oxidation processes. The development of new technologies to remove ICMs is needed. In this work, mackinawite (FeS)-activated sulfite autoxidation was employed for the degradation of IOP-containing water. The experiment was performed in a 500 mL self-made temperature-controlled reactor with online monitoring pH and dissolved oxygen in the laboratory. The effects of various parameters, such as initial pH values, sulfite dosages, FeS dosages, dissolved oxygen, and inorganic anions on the performance of the treatment process have been investigated. Eighty percent of IOP could be degraded in 15 min with 1 g L-1 FeS, 400 µmol L-1 sulfite at pH 8, and high efficiency on the removal of total organic carbon (TOC) was achieved, which is 71.8% via a reaction for 1 h. The generated hydroxyl and oxysulfur radicals, which contributed to the oxidation process, were identified through radical quenching experiments. The dissolved oxygen was essential for the degradation of IOP. The presence of Cl- could facilitate IOP degradation, while NO3- and CO32- could inhibit the degradation process. The reaction pathway involving H-abstraction and oxidative decarboxylation was proposed, based on product identification. The current system shows good applicability for the degradation of IOP and may help in developing a new approach for the treatment of ICM-containing water.

Antimicrobial Properties of MgO Nanostructures on Magnesium Substrates.

Magnesium (Mg) and its alloys have attracted increasing attention in recent years as medical implants for repairing musculoskeletal injuries because of their promising mechanical and biological properties. However, rapid degradation of Mg and its alloys in physiological fluids limited their clinical translation because the accumulation of hydrogen (H2) gas and fast release of OH- ions could adversely affect the healing process. Moreover, infection is a major concern for internally implanted devices because it could lead to biofilm formation, prevent host cell attachment on the implants, and interfere osseointegration, resulting in implant failure or other complications. Fabricating nanostructured magnesium oxide (MgO) on magnesium (Mg) substrates is promising in addressing both problems because it could slow down the degradation process and improve the antimicrobial activity. In this study, nanostructured MgO layers were created on Mg substrates using two different surface treatment techniques, i.e., anodization and electrophoretic deposition (EPD), and cultured with Staphylococcus aureus in vitro to determine their antimicrobial properties. At the end of the 24-h bacterial culture, the nanostructured MgO layers on Mg prepared by anodization or EPD both showed significant bactericidal effect against S. aureus. Thus, nanostructured MgO layers on Mg are promising for reducing implant-related infections and complications and should be further explored for clinical translation toward antimicrobial biodegradable implants.

Magnesium-based biodegradable microelectrodes for neural recording.

This article reports fabrication, characterization, degradation and electrical properties of biodegradable magnesium (Mg) microwires coated with two functional polymers, and the first in vivo evidence on the feasibility of Mg-based biodegradable microelectrodes for neural recording. Conductive poly(3,4­ethylenedioxythiophene) (PEDOT) coating was first electrochemically deposited onto Mg microwire surface, and insulating biodegradable poly(glycerol sebacate) (PGS) was then spray-coated onto PEDOT surface to improve the overall properties of microelectrode. The assembled PGS/PEDOT-coated Mg microelectrodes showed high homogeneity in coating thickness, surface morphology and composition before and after in vivo recording. The charge storage capacity (CSC) of PGS/PEDOT-coated Mg microwire (1.72 mC/cm2) was nearly 5 times higher than the standard platinum (Pt) microwire widely used in implantable electrodes. The Mg-based microelectrode demonstrated excellent neural-recording capability and stability during in vivo multi-unit neural recordings in the auditory cortex of a mouse. Specifically, the Mg-based electrode showed clear and stable onset response, and excellent signal-to-noise ratio during spontaneous-activity recordings and three repeats of stimulus-evoked recordings at two different anatomical locations in the auditory cortex. During 10 days of immersion in artificial cerebrospinal fluid (aCSF) in vitro, PGS/PEDOT-coated Mg microelectrodes showed slower degradation and less change in impedance than PEDOT-coated Mg electrodes. The biodegradable PGS coating protected the PEDOT coating from delamination, and prolonged the mechanical integrity and electrical properties of Mg-based microelectrode. Mg-based novel microelectrodes should be further studied toward clinical translation because they can potentially eliminate the risks and costs associated with secondary surgeries for removal of failed or no longer needed electrodes.

Antimicrobial Bioresorbable Mg-Zn-Ca Alloy for Bone Repair in a Comparison Study with Mg-Zn-Sr Alloy and Pure Mg.

Magnesium-zinc-calcium (Mg-Zn-Ca) alloys have attracted increasing attention for biomedical implant applications, especially for bone repair, because of their biocompatibility, biodegradability, and similar mechanical properties to human bone. The objectives of this study were to characterize Mg-2 wt % Zn-0.5 wt % Ca (named ZC21) alloy pins microstructurally and mechanically, and determine their degradation and interactions with host cells and pathogenic bacteria in vitro and in vivo in comparison with the previously studied Mg-4 wt % Zn-1 wt % strontium (named ZSr41) alloy and Mg control. Specifically, the in vitro degradation and cytocompatibility of ZC21 pins with bone marrow derived mesenchymal stem cells (BMSCs) were investigated using both direct culture and direct exposure culture methods. The adhesion density of BMSCs on ZC21 pins (i.e., direct contact) was significantly higher than on pure Mg pins in both in vitro culture methods; the cell adhesion density around ZC21 pins (i.e., indirect contact) was similar to the cell-only positive control in both in vitro culture methods. Interestingly, ZC21 showed a higher daily degradation rate, crack width and crack area ratio in the direct exposure culture than in the direct culture, suggesting different culture methods did affect its in vitro degradation behaviors. When cultured with Gram-positive bacteria methicillin-resistant Staphylococcus aureus (MRSA), ZC21 reduced bacterial adhesion on the surface more significantly than that of ZSr41 and Mg. The in vivo degradation and biocompatibility of the ZC21 pins for bone regeneration were studied in a mouse femoral defect model. The in vivo degradation rate of ZC21 pins was much slower than that of ZSr41 alloy and Mg control pins. After 12 weeks of implantation in vivo, the ZC21 group showed the shortest gap at the femoral defect, indicating that ZC21 pins promoted osteogenesis and bone healing more than ZSr41 and Mg control pins. Overall, the ZC21 alloy is promising for bone repair, while providing antibacterial activities, and should be further studied toward clinical translation.

Engineering Nano-to-Micron-Patterned Polymer Coatings on Bioresorbable Magnesium for Controlling Human Endothelial Cell Adhesion and Morphology.

Surface patterning is an attractive approach to modify the surface of biomaterials for modulating cell activities and enhancing the performance of medical implants without involving typical chemical changes to the implants such as adding growth factors, antibiotics, and drugs. In this study, nano-to-micron patterns were engineered on thermoplastic and thermoset polymer coatings on bioresorbable magnesium (Mg) substrates to control the cellular responses and material degradation for vascular applications. Capillary force lithography (CFL) was modified and integrated with spray coating to fabricate well-aligned nano-to-micron patterns on the thermoplastic poly(lactic-co-glycolic acid) (PLGA) and thermoset poly(glycerol sebacate) (PGS) coatings on Mg substrates. Specifically, a new process of molding-curing CFL was revised from the conventional CFL to successfully create nano-to-submicron patterns on thermoset PGS for the first time. The nano-to-micron-patterned polymer coatings of PLGA and PGS on Mg were carefully characterized, and their effects on cell adhesion and morphology were investigated through direct culture with human umbilical vein endothelial cells (HUVECs) in vitro. The results showed that the 3000 nm parallel grooves could effectively elongate the HUVECs, while the 740 nm parallel grooves tended to reduce the spreading of HUVECs. The PLGA coatings reduced the degradation of Mg substrates more than that of the PGS coatings in the direct culture with HUVECs in vitro. CFL-based methods coupled with spray coating should be further studied as a nonchemical approach for creating nano-to-micron-patterned polymer coatings on Mg-based substrates of various sizes and shapes, which may present a new direction for improving the performance of Mg-based bioresorbable vascular devices toward potential clinical translation.

Degradation behaviors and cytocompatibility of Mg/ß-tricalcium phosphate composites produced by spark plasma sintering.

Magnesium (Mg)-based materials have shown great potentials for bioresorbable implant applications. Previous studies showed that Mg with 10 and 20 vol % ß-tricalcium phosphate (ß-TCP) composites produced by spark plasma sintering, improved mechanical properties when compared with pure Mg. The objectives of this study were to evaluate the degradation behaviors of Mg/10% ß-TCP and Mg/20% ß-TCP composites in revised stimulated body fluid (rSBF), and to determine their cytocompatibility with bone marrow derived mesenchymal stem cells (BMSCs) using the direct culture method. During the 11 days of immersion in rSBF, Mg/ß-TCP composites showed different degradation behaviors at different immersion periods, that is, the initial stage (0-1 hr), the mid-term stage (1 hr to 2 days), and the long-term stage (2-11 days). The counter effects of mass loss due to microgalvanic corrosion and mass gain due to deposition of Ca-P containing layers resulted in slower Mg2+ ion release for Mg/20% ß-TCP than Mg/10% ß-TCP in the mid-term, but eventually 16% mass loss for Mg/20% ß-TCP and 10% mass loss for Mg/10% ß-TCP after 11 days of immersion. The in vitro studies with BMSCs showed the highest cell adhesion density (i.e., 68% of seeding density) on the plate surrounding the Mg/10% ß-TCP sample, that is, under the indirect contact condition of direct culture. The ß-TCP showed a positive effect on direct adhesion of BMSCs on the surface of Mg/ß-TCP composites. This study elucidated the degradation behaviors and the cytocompatibility of Mg/ß-TCP composites in vitro; and, further studies on Mg/ceramic composites are needed to determine their potential for clinical applications. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2238-2253, 2019.

Responses of human urothelial cells to magnesium-zinc-strontium alloys and associated insoluble degradation products for urological stent applications.

Current urological devices such as ureteral stents and catheters still face serious problems, such as encrustation and biofilm formation. Magnesium (Mg) and its alloys showed great potentials as an alternative material for urological devices, due to their excellent biodegradability and antibacterial property. In this study, a serial of four promising Mg alloys which contain zinc (Zn) and strontium (Sr), i.e., Mg-4Zn-xSr (ZSr41) alloys, were investigated in vitro for potential ureteral stent application. Specifically, these four alloys have 4 wt% Zn in all and 0.15 wt% Sr in ZSr41_A, 0.5 wt% Sr in ZSr41_B, 1.0 wt% Sr in ZSr41_C and 1.5 wt% Sr in ZSr41_D. The cytocompatibility and degradation behaviors of Mg-4Zn-xSr alloys were studied by culturing with human urothelial cells (HUCs) for 24 h and 48 h using exposure culture method. ZSr41_B showed a better cytocompatibility with HUCs among all the Mg-4Zn-xSr alloys in both 24-hour and 48-hour cultures. Moreover, the cytocompatibility of insoluble degradation products of Mg, i.e., MgO and Mg(OH)2, was also investigated by culturing different concentrations of MgO and Mg(OH)2 nanoparticles with HUCs for 24 h and 48 h. The concentration of MgO and Mg(OH)2 particles at 0.5 mg/mL and above, showed a significant decrease of cell density and cell size after 24-hour and 48-hour cultures. The concentration of MgO and Mg(OH)2 at 1.0 mg/mL and above, showed no viable cells after 24-hour culture. Collectively, it is recommended to further reduce the degradation rates of Mg alloys in order to control possible side effects of the soluble and insoluble degradation products and to take the benefits of Mg-based biodegradable ureteral stents toward the future clinical translation.

In vitro evaluation of MgSr and MgCaSr alloys via direct culture with bone marrow derived mesenchymal stem cells.

Magnesium (Mg) and its alloys have been widely investigated as the most promising biodegradable metals to replace conventional non-degradable metals for temporary medical implant applications. New Mg alloys have been developed for medical applications in recent years; and the concept of alloying Mg with less-toxic elements have aroused tremendous interests due to the promise to address the problems associated with rapid degradation of Mg without compromising its cytocompatibility and biocompatibility. Of particular interests for orthopedic/spinal implant applications are the additions of calcium (Ca) and strontium (Sr) into Mg matrix because of their beneficial properties for bone regeneration. In this study, degradation and cytocompatibility of four binary MgSr alloys (Mg-xSr, x = 0.2, 0.5, 1 and 2 wt%) and four ternary MgCaSr alloys (Mg-1Ca-xSr, x = 0.2, 0.5, 1 and 2 wt%) were investigated and compared via direct culture with bone marrow-derived mesenchymal stem cells (BMSCs). The influence of the alloy composition on the degradation rates were studied and compared. Moreover, the cellular responses to the binary MgSr alloys and the ternary MgCaSr alloys were comparatively evaluated; and the critical factors influencing BMSC behaviors were discussed. This study screened the degradability and in vitro cytocompatibility of the binary MgSr alloys and the ternary MgCaSr alloys. Mg-1Sr, Mg-1Ca-0.5Sr and Mg-1Ca-1Sr alloys are recommended for further in vivo studies toward clinical translation due to their best overall performances in terms of degradation and cytocompatibility among all the alloys studied in the present work. STATEMENT OF SIGNIFICANCE: Traditional Mg alloys with slower degradation often contain aluminum or rare earth elements as alloying components, which raised safety and regulatory concerns. To circumvent unsafe elements, nutrient elements such as calcium (Ca) and strontium (Sr) were selected to create Mg-Sr binary alloys and Mg-Ca-Sr ternary alloys to improve the safety and biocompatibility of bioresorbable Mg alloys for medical implant applications. In this study, in vitro degradation and cellular responses to four binary Mg-xSr alloys and four ternary Mg-1Ca-xSr alloys with increasing Sr content (up to 2 wt%) were evaluated in direct culture with bone marrow derived mesenchymal stem cells (BMSCs). The roles of Sr and Ca in tuning the alloy microstructure, degradation behaviors, and BMSC responses were collectively compared in the BMSC direct culture system for the first time. The most promising alloys were identified and recommended for further in vivo studies toward clinical translation.

Electrochemical deposition of conductive polymers onto magnesium microwires for neural electrode applications.

Metals are widely used in electrode design for recording neural activities because of their excellent electrical conductivity and mechanical strength. However, there are still serious problems related to these currently used metallic electrodes, including tissue damage due to the mechanical mismatch between metals and neural tissues, fibrosis, and electrode fouling and encapsulation that lead to the loss of signal and eventual failure. In this study, a biocompatible, biodegradable, and conductive electrode was created. Specifically, pure magnesium (Mg) microwire with a diameter of 127 µm was used as the electrode substrate and the conductive polymer, that is, poly(3,4-ethylenedioxythiophene) (PEDOT), was electrochemically deposited onto Mg microwires to decrease corrosion rate and improve biocompatibility of the electrodes for potential neural electrode applications. Both chronopotentiometry and cyclic voltammetry (CV) methods and the associated parameters for electrochemical deposition of PEDOT onto Mg microwires were investigated, such as deposition current, deposition temperature, voltage, sweep rate, cycle number, and duration. The CV method from -2.0 to 1.25 V for 1 cycle at a cycle duration of 600 s with a sweep rate of 5 mV/s at 65°C led to a consistent, uniform, and complete PEDOT coating on Mg microwires. The surface conditions of Mg microwires also affected the quality of PEDOT coating. The corrosion rate of PEDOT-coated Mg microwire was 0.75 mm/year, much slower than the noncoated Mg microwire that showed a corrosion rate of 1.78 mm/year. The optimal Mg microwires with PEDOT coating could potentially serve as biodegradable electrodes for neural recording and stimulation applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1887-1895, 2018.

[Calculation model of urban water resources ecological footprint and its application: a case study in Shenyang City of Northeast China].

Water resources ecological footprint can directly reflect the pressure of human social and economic activities to water resources, and provide important reference for the rational utilization of water resources. Based on the existing ecological footprint models and giving full consideration of the water resources need of urban ecological system, this paper established a new calculation model of urban water resources ecological footprint, including domestic water account, process water account, public service water account, and ecological water requirement account. According to the actual situation of Shenyang City, the key parameters of the model were determined, and the water resources ecological footprint and ecological carrying capacity of the City were calculated and analyzed. From 2000 to 2009, the water resources ecological footprint per capita of the City presented an overall decreasing trend, but still had an annual ecological deficit. As compared to that in 2000, the water resources ecological footprint per capita was decreased to 0.31 hm2 in 2005, increased slightly in 2006 and 2007, and remained stable in 2008 and 2009, which suggested that the sustainable utilization of water resources in Shenyang City had definite improvement, but was still in an unsustainable development situation.

Synthesis of uniform hollow silica spheres with ordered mesoporous shells in a CO2 induced nanoemulsion.

Monodisperse hollow silica spheres of uniform size and ordered mesoporous shells have been successfully fabricated in water/heptane/CTAB nanoemulsions induced by compressed CO(2).

Enhanced stabilization of vesicles by compressed CO2.

In this work, we studied the effect of compressed CO2 on the stability of vesicles formed in a dodecyltrimethylammonium bromide (DTAB)/sodium dodecyl sulfate (SDS) mixed surfactant system by combination of phase behavior and turbidity study, and UV-vis and fluorescence techniques. It was discovered that compressed CO2 could enhance the stability of vesicles significantly. This new and effective method to stabilize vesicles has some unique advantages over conventional methods. For example, the size and stability of the vesicles can be easily controlled by CO2 pressure; the method is greener because CO2 is a green reagent and it can be released completely after depressurization, which simplifies postseparation processes in applications. The main reason for CO2 to stabilize the vesicles is that CO2 molecules can insert into the hydrophobic bilayer region to enhance the rigidity of the vesicle film and reduce the size of the vesicles, which is different from that of conventional cosolvents (e.g., alcohols) used to stabilize vesicles. On the basis of this discovery, we developed a method to prepare hollow silica spheres using tetraethoxysilane as the precursor and CO2-stabilized vesicles as the template, in which CO2 acts as both the stabilizer of the vesicular template and the catalyst for the hydrolysis reaction of the precursor, and other cosolvents and catalysts are not required. Besides, the size of the silica hollow spheres prepared can be controlled by the pressure of CO2.

Formation of micelles of Pluronic block copolymers in PEG 200.

The formation of micelles of Pluronic block copolymers in poly(ethylene glycol) (PEG) was studied using fluorescence, solubilization measurements, and frozen fracture electron microscopy (FFEM) methods at 40 degrees C. It was discovered that surfactants L44 (EO(10)PO(23)EO(10)), P85 (EO(26)PO(40)EO(26)), and P105 (EO(37)PO(56)EO(37)) can form micelles in PEG 200 (PEG with a nominal molecular weight of 200), and the critical micellization concentration (CMC) decreases with increasing molecular weight of the surfactants. The size of the micelles formed by these Pluronic block copolymers is in the range of 6-35 nm. The CMC values in PEG 200 are higher than those in aqueous solutions.

Effect of compressed CO2 on the properties of lecithin reverse micelles.

Lecithin is a very useful biosurfactant. In this work, the effects of compressed CO 2 on the critical micelle concentration (cmc) of lecithin in cyclohexane and solubilization of water, lysozyme, and PdCl 2 in the lecithin reverse micelles were studied. The micropolarity and pH value of the polar cores of the reverse micelles with and without CO 2 were also investigated. It was found that CO 2 could reduce the cmc of the micellar solution and enhance the capacity of the reverse micelles to solubilize water, the biomolecule, and the inorganic salt significantly. Moreover, the water pools could not be formed in the reverse micelles in the absence of CO 2 because of the limited amount of water solubilized. However, the water pools could be formed in the presence of CO 2 because large amounts of water could be solubilized. All of these provide more opportunity for effective utilization of this green surfactant. The possible mechanism for tuning the properties of the reverse micelles by CO 2 is discussed.

Synthesis of alpha-chymotrypsin/polymer composites by a reverse micelle/gas antisolvent method.

Alpha-chymotrypsin (CT)/polyvinylpyrrolidone (PVP) composites was synthesized by combination of reverse micelles and CO(2). In this method, the two reverse micellar solutions containing CT and PVP, respectively, were first mixed, then compressed CO(2) was used as an antisolvent to precipitate the CT and PVP simultaneously and CT/PVP composites were successfully prepared. The morphology of the obtained CT/PVP composites was characterized by transmission electron microscopy (TEM). The FTIR spectra of the composites showed that there was interaction between CT and PVP. The storage activity of the enzyme immobilized on the polymer by this method was higher than that of the pure enzyme. This method has some advantages and can be easily applied to the synthesis of some other enzyme/polymer composites.