Synergistic Approaches in the Design and Applications of UCST Polymers

This review summarizes recent progress in the synergistic design strategy for thermoresponsive polymers possessing an upper critical solution temperature (UCST) in aqueous systems. To achieve precise control of the responsive behavior of the UCST polymers, their molecular design can benefit from a synergistic effect of hydrogen bonding with other interactions or modification of the chemical structures. The combination of UCST behavior with other stimuli-responsive properties of the polymers may yield new functional materials with potential applications such as sensors, actuators, and controlled release devices. The advances in this area provide insight or inspiration into the understanding and design of functional UCST polymers for a wide range of applications.

Targeting autophagy in Alzheimer's disease: Animal models and mechanisms

Alzheimer's disease (AD) is an age-related progressive neurodegenerative disorder that leads to cognitive impairment and memory loss. Emerging evidence suggests that autophagy plays an important role in the pathogenesis of AD through the regulation of amyloid-beta (Aβ) and tau metabolism, and that autophagy dysfunction exacerbates amyloidosis and tau pathology. Therefore, targeting autophagy may be an effective approach for the treatment of AD. Animal models are considered useful tools for investigating the pathogenic mechanisms and therapeutic strategies of diseases. This review aims to summarize the pathological alterations in autophagy in representative AD animal models and to present recent studies on newly discovered autophagy-stimulating interventions in animal AD models. Finally, the opportunities, difficulties, and future directions of autophagy targeting in AD therapy are discussed.

[Recommendations for the diagnosis and treatment of gout in China]

Gout is a metabolic disease resulting from the accumulation of monosodium urate (MSU) in joints, leading to crystal-induced arthritis. In China, gout is common, but there is insufficient knowledge regarding standardized criteria for the diagnosis and treatment of this condition. Based on evidence and guidelines from China and other countries, the Chinese Rheumatology Association developed standardized criteria for the diagnosis and treatment of gout in China. The purpose was to standardize gout diagnosis methods as well as treatment opportunities and strategies in order to reduce misdiagnosis, missed diagnosis, and irreversible damage.

Lipase-catalyzed ring-opening polymerization of natural compound-based cyclic monomers

The need for sustainable and environment-friendly materials has led to growing interest in the development of biodegradable polymers based on natural compounds. However, metal-based catalysts used in the polymerization process may cause concerns about the toxicity of the resultant polymers. Therefore, polymers derived from natural compounds and synthesized through the use of green catalysts are highly desirable. Lipase-catalyzed ring-opening polymerization (ROP) of biocompound-based cyclic monomers has emerged as a promising and green strategy for the design and synthesis of such polymers. In this review, we summarize reports on the use of ROP catalyzed by lipase for cyclic monomers derived from natural compounds, including bile acid- and porphyrin-based macrocycles, carbonate-based macrocycles, lactones, and cyclic anhydrides, with an emphasis on ring-closure reactions for the synthesis of cyclic monomers, the types of lipases for the ROP and the choice of reaction conditions (temperature, solvent, reaction time, etc.). Moreover, the current challenges and perspectives for the choice and reusability of lipases, ring-closure versus ring-opening reactions, monomer design, and potential applications are discussed.

Production of MSTN knockout porcine cells using adenine base-editing-mediated exon skipping

Gene-knockout pigs have important applications in agriculture and medicine. Compared with CRISPR/Cas9 and cytosine base editing (CBE) technologies, adenine base editing (ABE) shows better safety and accuracy in gene modification. However, because of the characteristics of gene sequences, the ABE system cannot be widely used in gene knockout. Alternative splicing of mRNA is an important biological mechanism in eukaryotes for the formation of proteins with different functional activities. The splicing apparatus recognizes conserved sequences of the 5' end splice donor and 3' end splice acceptor motifs of introns in pre-mRNA that can trigger exon skipping, leading to the production of new functional proteins, or causing gene inactivation through frameshift mutations. This study aimed to construct a MSTN knockout pig by inducing exon skipping with the aid of the ABE system to expand the application of the ABE system for the preparation of knockout pigs. In this study, first, we constructed ABEmaxAW and ABE8eV106W plasmid vectors and found that their editing efficiencies at the targets were at least sixfold and even 260-fold higher than that of ABEmaxAW by contrasting the editing efficiencies at the gene targets of endogenous CD163, IGF2, and MSTN in pigs. Subsequently, we used the ABE8eV106W system to realize adenine base (the base of the antisense strand is thymine) editing of the conserved splice donor sequence (5'-GT) of intron 2 of the porcine MSTN gene. A porcine single-cell clone carrying a homozygous mutation (5'-GC) in the conserved sequence (5'-GT) of the intron 2 splice donor of the MSTN gene was successfully generated after drug selection. Unfortunately, the MSTN gene was not expressed and, therefore, could not be characterized at this level. No detectable genomic off-target edits were identified by Sanger sequencing. In this study, we verified that the ABE8eV106W vector had higher editing efficiency and could expand the editing scope of ABE. Additionally, we successfully achieved the precise modification of the alternative splice acceptor of intron 2 of the porcine MSTN gene, which may provide a new strategy for gene knockout in pigs.

[Artificial intelligence technology enables ultrasonography in precision diagnosisand treatment of liver diseases]

Liver disease is one of the major problems affecting human health. Ultrasound plays an important role in diagnosis and treatment of diffuse and focal liver diseases. However, conventional ultrasound evaluation is subjective and provides limited information. Artificial intelligence (AI) technology may supplement the disadvantages of conventional ultrasound and has been widely used in the field of ultrasound in liver diseases. To date, remarkable progress has been achieved for the use of AI technology in the diagnosis, assessment of therapeutic efficacy and prognosis prediction of liver diseases. This paper reviews the research progress of ultrasound image-based AI technology in the diagnosis and treatment of diffuse and focal liver diseases.

[Recommendations for diagnosis and treatment of systemic sclerosis in China]

Systemic sclerosis (SSc) is an autoimmune rheumatic disease that is characterized by skin fibrosis with multi-organ involvement. In China, the standardized diagnosis and treatment for SSc is still lacking. Based on the diagnosis criteria and guidelines from China and abroad, Chinese Rheumatology Association developed the current standardization of diagnosis and treatment for SSc. The purposes of this guideline are to standardize clinical management for SSc in China, to interpret the key evaluation tools for SSc, and to recommend therapeutic principle and strategies.

Using Nuclear Magnetic Resonance Spectroscopy to Probe Hydrogels Formed by Sodium Deoxycholate

Hydrogels of bile acids and their salts are promising materials for drug delivery, cellular immobilization, and other applications. However, these hydrogels are poorly understood at the molecular level, and further study is needed to allow improved materials to be created by design. We have used NMR spectroscopy to probe hydrogels formed from mixtures of formic acid and sodium deoxycholate (NaDC), a common bile acid salt. By assaying the ratio of deoxycholate molecules that are immobilized as part of the fibrillar network of the hydrogels and those that can diffuse, we have found that 65% remain free under typical conditions. The network appears to be composed of both the acid and salt forms of deoxycholate, possibly because a degree of charge inhibits excessive aggregation and precipitation of the fibrils. Spin-spin relaxation times provided a molecular-level estimate of the temperature of gel-sol transition (42 °C), which is virtually the same as the value determined by analyzing macroscopic parameters. Saturation transfer difference (STD) NMR spectroscopy established that formic acid, which is present mainly as formate, is not immobilized as part of the gelating network. In contrast, HDO interacts with the network, which presumably has a surface with exposed hydrophilic groups that form hydrogen bonds with water. Moreover, the STD NMR experiments revealed that the network is a dynamic entity, with molecules of deoxycholate associating and dissociating reversibly. This exchange appears to occur preferentially by contact of the hydrophobic edges or faces of free molecules of deoxycholate with those of molecules immobilized as components of the network. In addition, DOSY experiments revealed that gelation has little effect on the diffusion of free NaDC and HDO.

[Recommendations of diagnosis and treatment of adult-onset Still's disease in China]

Adult-onset Still's disease (AOSD) is a rare systemic autoinflammatory disorder. In China, standardized diagnosis and treatment for AOSD is insufficient. Based on the evidence from China and other countries, Chinese Rheumatology Association developed standardization of diagnosis and treatment of AOSD in China. The purpose is to standardize the methods for diagnosis of AOSD, treatment strategies, and reduce misdiagnosis, missed diagnosis and irreversible damage.

Smart microneedle patches for rapid, and painless transdermal insulin delivery

Insulin administration at mealtimes for the control of postprandial glucose is a major part of basal-bolus insulin therapy; however, painful subcutaneous (SC) injections lead to poor patient compliance. The microneedle (MN) patch, which allows painless transdermal drug delivery, is a promising substitute; however, it remains a big challenge to deliver insulin as rapidly as by SC injection. Here a novel MN patch is designed in which the MNs are coated with insulin/poly-l-glutamic acid (PGA) layer-by-layer (LBL) films at pH 3.0. This coating is pH-sensitive because the net charge of insulin turns from positive to negative when the pH increases from 3.0 to 7.4. As a result, when transferred to pH 7.4 media, e.g., when inserted into skin, the coating dissociates instantly and releases insulin rapidly. A brief epidermal application (<1 min) of the coated MNs is enough for complete film dissociation. More importantly, the coated MN patch exhibits a pharmacokinetic and a pharmacodynamic profile comparable to that of insulin administrated by SC injection, suggesting the coated MN patch can deliver insulin as rapidly as the SC injection. In addition, the patch exhibits excellent biocompatibility and storage stability. The new MN patch is expected to become a painless, convenient method for the control of postprandial glucose.

Functional fillers for dental resin composites

Dental resin composites (DRCs) are popular materials to repair caries. Although various types of DRCs with different characteristics have been developed, restoration failures still exist. Bulk fracture and secondary caries have been considered as main causes for the failure of composites restoration. To address these problems, various fillers with specific functions have been introduced and studied. Some fillers with specific morphologies such as whisker, fiber, and nanotube, have been used to increase the mechanical properties of DRCs, and other fillers releasing ions such as Ag⁺, Ca²⁺, and F^-, have been used to inhibit the secondary caries. These functional fillers are helpful to improve the performances and lifespan of DRCs. In this article, we firstly introduce the composition and development of DRCs, then review and discuss the functional fillers classified according to their roles in the DRCs, finally give a summary on the current research and predict the trend of future development.

CRISPR/Cas9-mediated MSTN disruption accelerates the growth of Chinese Bama pigs

CRISPR/Cas9-mediated genome editing technology is a simple and highly efficient and specific genome modification approach with wide applications in the animal industry. CRISPR/Cas9-mediated genome editing combined with somatic cell nuclear transfer rapidly constructs gene-edited somatic cell-cloned pigs for the genetic improvement of traits or simulation of human diseases. Chinese Bama pigs are an excellent indigenous minipig breed from Bama County of China. Research on genome editing of Chinese Bama pigs is of great significance in protecting its genetic resource, improving genetic traits and in creating disease models. This study aimed to address the disadvantages of slow growth and low percentage of lean meat in Chinese Bama pigs and to knock out the myostatin gene (MSTN) by genome editing to promote growth and increase lean meat production. We first used CRISPR/Cas9-mediated genome editing to conduct biallelic knockout of the MSTN, followed by somatic cell nuclear transfer to successfully generate MSTN biallelic knockout Chinese Bama pigs, which was confirmed to have significantly faster growth rate and showed myofibre hyperplasia when they reached sexual maturity. This study lays the foundation for the rapid improvement of production traits of Chinese Bama pigs and the generation of gene-edited disease models in this breed.

[Recommendations of diagnosis and treatment of gout in China]

Gout is a crystal associated arthritis caused by monosodium urate (MSU) accumulating in joint, and it belongs to metabolic rheumatic disease. In China, gout is common but it is insufficient for education of standardized diagnosis and treatment for gout. Based on the evidence and guidelines from China and other countries, Chinese gout Collaborative Research Group developed standardization of diagnosis and treatment of gout in China. The purpose is to standardize the methods for diagnosis of gout, treatment opportunity and strategies in order to reduce misdiagnosis, missed diagnosis and irreversible damage.

[Study on fibrosis changes in the lungs of mice caused by repeated inhalation of polyhexamethyleneguaidine disinfectant]

Objective: To explore the lung damage caused by repeated inhalation of polyhexamethyleneguanidine (PHMG) disinfectant aerosol and the corresponding toxicological characteristics. Methods: Thirty four-week-old mice of C57BL/6N strain were randomly divided into three groups, the control group, low-dose group, and high-dose group. Each group had 5 male mice and 5 female mice. Lab II-level purified water was used in the control group. The PHMG disinfectant aerosol was generated by using the ultrasonic atomization of the aqueous solution containing PHMG. The PHMG concentrations in the low-and high-dose groups were 0.1 mg/ml (0.01%) and 1 mg/ml (0.1%), respectively. The concentration of PHMG in the post-chemical exposure room was 1.03 mg/m(3) and 9.09 mg/m(3) according to the air sampler analysis. The experimental mice were exposed to the PHMG in dynamic respiratory exposure mode for 4 hours every day in 21 days. After 21-day exposure, bronchia alveolus lung fluids (BALFs) were used to evaluate the inflammatory cells in the lungs, and pathological evaluation, special staining and immunohistochemical methods were further performed to evaluate the key indicators of pulmonary fibrosis. Results: Compared to the control group, the body weight of mice in the high-dose group was significantly decreased (P<0.05), while that of mice in the low-dose group did not significantly differ (P>0.05). The number of inflammatory cells in BALFs of low-dose exposed mice was slightly reduced, and the lung tissue pathology began to show lung damage with early fibrosis symptoms (P<0.05). The pathological examination of mice in the high-dose group showed changes in pulmonary fibrosis. Immunohistochemical staining showed that pulmonary fibrosis marker, α-SMA, was significantly increased in low-dose group and high-dose group (P<0.05). Conclusion: The repeated inhalation of PHMG disinfectant could cause lung damage such as pulmonary fibrosis in mice. It could suggest that special warnings should be given to this common disinfectant and respiratory protection measures should be adopted during industrial production and daily use.

Efficient generation of GHR knockout Bama minipig fibroblast cells using CRISPR/Cas9-mediated gene editing

Dwarfism, also known as growth hormone deficiency (GHD), is a disease caused by genetic mutations that result in either a lack of growth hormone or insufficient secretion of growth hormone, resulting in a person's inability to grow normally. In the past, many studies focusing on GHD have made use of models of other diseases such as metabolic or infectious diseases. A viable GHD specific model system has not been used previously, thus limiting the interpretation of GHD results. The Bama minipig is unique to Guangxi province and has strong adaptability and disease resistance, and an incredibly short stature, which is especially important for the study of GHD. In addition, studies of GHR knockout Bama minipigs and GHR knockout Bama minipig fibroblast cells generated using CRISPR/Cas9 have not been previously reported. Therefore, the Bama minipig was selected as an animal model and as a tool for the study of GHD in this work. In this study, a Cas9 plasmid with sgRNA targeting the first exon of the GHR gene was transfected into Bama minipig kidney fibroblast cells to generate 22 GHR knockout Bama minipig kidney fibroblast cell lines (12 male monoclonal cells and 10 female monoclonal cells). After culture and identification, 11 of the 12 male clone cell lines showed double allele mutations, and the rate of positive alteration of GHR was 91.67%. Diallelic mutation of the target sequence occurred in 10 female clonal cell lines, with an effective positive mutation rate of 100%. Our experimental results not only showed that CRISPR/Cas9 could efficiently be used for gene editing in Bama minipig cells but also identified a highly efficient target site for the generation of a GHR knockout in other porcine models. Thus, the generation of GHR knockout male and female Bama fibroblast cells could lay a foundation for the birth of a future dwarfism model pig. We anticipate that the "mini" Bama minipig will be of improved use for biomedical and agricultural scientific research and for furthering our understanding of the genetic underpinnings of GHD.

[Clinical applications of intelligent pressure control flexible ureteroscope for the treatment of renal calculi ≤2 cm]

Objective: To evaluate the effectiveness and safety of intelligent pressure control flexible ureteroscope for management of renal stones ≤2 cm. Methods: The clinical data of 267 cases of renal calculi treated with flexible ureteroscope lithotripsy at Department of Urology, Ganzhou People's Hospital from June 2015 to December 2017 were analyzed retrospectively. There were 129 male and 138 female patients, with a mean age of 51.2 years (ranging from 19 to 76 years). Among them, 145 patients underwent intelligent pressure control flexible ureteroscope (intelligent control group) and 122 patients underwent flexible ureteroscope ordinary (ordinary group). The t test, χ² test or Fisher exact test were used for statistical analysis. The success rate of stone seeking, the stone free rates, the incidence of complications, the average operation time, the average hospital stay after operation were compared between the two groups. Results: The average mean operative time of the patients with intelligent control group was (26.17 ± 8.64) minutes, significantly shorter than (47.23±18.35) minutes of the ordinary group (t=1.968, P=0.000). The stone free rate of the patients with intelligent control group was 97.2%, it was higher than 86.0% of ordinary group (χ²=0.069, P=0.004). The complication rate of the patients with intelligent control group was 2.7%, which was significantly shorter than 18.0% of the ordinary group (χ²=17.586, P=0.000). However, there was no significant difference between the two groups in the success rate of stone seeking and postoperative hospital stay (P>0.05). Conclusion: Intelligent controlled pressure ureteral flexible ureteroscope has the advantages of short operation time, high stone free rate and less complications in the treatment of renal calculi ≤2 cm compared with flexible ureteroscope ordinary.

Generation of transgenic-cloned Huanjiang Xiang pigs systemically expressing enhanced green fluorescent protein

Huanjiang Xiang pig is a unique native minipig breed originating in Guangxi, China, and has great utility value in agriculture and biomedicine. Reproductive biotechnologies such as somatic cell nuclear transfer (SCNT) and SCNT-mediated genetic modification show great potential value in genetic preservation and utilization of Huanjiang Xiang pigs. Our previous work has successfully produced cloned and transgenic-cloned embryos using somatic cells from a Huanjiang Xiang pig. In this study, we firstly report the generation of transgenic-cloned Huanjiang Xiang pigs carrying an enhanced green fluorescent protein (eGFP) gene. A total of 504 SCNT-derived embryos were transferred to two surrogate recipients, one of which became pregnant and gave birth to three live piglets. Exogenous eGFP transgene had integrated in all of the three Huanjiang Xiang piglets identified by genotyping. Furthermore, expression of eGFP was also detected from in vitro cultured skin fibroblast cells and various organs or tissues from positive transgenic-cloned Huanjiang Xiang pigs. The present work provides a practical method to preserve this unique genetic resource and also lays a foundation for genetic modification of Huanjiang Xiang pigs with improved values in agriculture and biomedicine.

CRISPR/Cas9-Mediated Generation of Guangxi Bama Minipigs Harboring Three Mutations in α-Synuclein Causing Parkinson's Disease

Parkinson’s disease (PD) is a common, progressive neurodegenerative disorder characterized by classical motor dysfunction and is associated with α-synuclein-immunopositive pathology and the loss of dopaminergic neurons in the substantia nigra (SN). Several missense mutations in the α-synuclein gene SCNA have been identified as cause of inherited PD, providing a practical strategy to generate genetically modified animal models for PD research. Since minipigs share many physiological and anatomical similarities to humans, we proposed that genetically modified minipigs carrying PD-causing mutations can serve as an ideal model for PD research. In the present study, we attempted to model PD by generating Guangxi Bama minipigs with three PD-causing missense mutations (E46K, H50Q and G51D) in SCNA using CRISPR/Cas9-mediated gene editing combining with somatic cell nuclear transfer (SCNT) technique. We successfully generated a total of eight SCNT-derived Guangxi Bama minipigs with the desired heterozygous SCNA mutations integrated into genome, and we also confirmed by DNA sequencing that these minipigs expressed mutant α-synuclein at the transcription level. However, immunohistochemical analysis was not able to detect PD-specific pathological changes such as α-synuclein-immunopositive pathology and loss of SN dopaminergic neurons in the gene-edited minipigs at 3 months of age. In summary, we successfully generated Guangxi Bama minipigs harboring three PD-casusing mutations (E46K, H50Q and G51D) in SCNA. As they continue to develop, these gene editing minipigs need to be regularly teseted for the presence of PD-like pathological features in order to validate the use of this large-animal model in PD research.

Andrographolide disrupts meiotic maturation by blocking cytoskeletal reorganisation and decreases the fertilisation potential of mouse oocytes

Andrographolide (AG) is a diterpenoid lactone isolated from the stem and leaves of Andrographis paniculata Nees that is used for the effective treatment of infectious diseases in Asian countries. Previous studies have reported adverse effects of AG on female fertility in rodents; however, the underlying mechanisms are unknown. The aim of the present study was to investigate the effects of AG on the IVM of mouse oocytes and their fertilisation potential. Immature oocytes incubated for 6, 14 or 24h in medium containing 5, 10 or 20μM AG showed time- and dose-dependent decreases in maturation rates compared with the control group. Immunostaining revealed that AG exposure disrupted spindle organisation and migration, as well as actin cap formation and cytokinesis. Furthermore, most oocytes exposed to 20μM AG underwent apoptosis, and the few oocytes exposed to 5 or 10μM AG that reached MII exhibited lower fertilisation rates after intracytoplasmic sperm injection. The findings of the present study suggest that AG may disrupt mouse oocyte meiotic maturation by blocking cytoskeletal reorganisation, and may thus have an adverse effect on female fertility.

Bile Acid-Based Drug Delivery Systems for Enhanced Doxorubicin Encapsulation: Comparing Hydrophobic and Ionic Interactions in Drug Loading and Release

Doxorubicin (Dox) is a drug of choice in the design of drug delivery systems directed toward breast cancers, but is often limited by loading and control over its release from polymer micelles. Bile acid-based block copolymers present certain advantages over traditional polymer-based systems for drug delivery purposes, since they can enable a higher drug loading via the formation of a reservoir through their aggregation process. In this study, hydrophobic and electrostatic interactions are compared for their influence on Dox loading inside cholic acid based block copolymers. Poly(allyl glycidyl ether) (PAGE) and poly(ethylene glycol) (PEG) were grafted from the cholic acid (CA) core yielding a star-shaped block copolymer with 4 arms (CA-(PAGE- b-PEG)₄) and then loaded with Dox via a nanoprecipitation technique. A high Dox loading of 14 wt % was achieved via electrostatic as opposed to hydrophobic interactions with or without oleic acid as a cosurfactant. The electrostatic interactions confer a pH responsiveness to the system. 50% of the loaded Dox was released at pH 5 in comparison to 12% at pH 7.4. The nanoparticles with Dox loaded via hydrophobic interactions did not show such a pH responsiveness. The systems with Dox loaded via electrostatic interactions showed the lowest IC₅₀ and highest cellular internalization, indicating the pre-eminence of this interaction in Dox loading. The blank formulations are biocompatible and did not show cytotoxicity up to 0.17 mg/mL. The new functionalized star block copolymers based on cholic acid show great potential as drug delivery carriers.

[DNT cell inhibits the growth of pancreatic carcinoma via NKG2D and MICA pathway in vivo]

Objective: To investigate the effects of natural killer group 2 member D (NKG2D) and its ligands major histocompatibility complex class Ⅰ chain-related molecules A(MICA) on DNT cell killing pancreatic carcinoma. Methods: Antibodies adsorption was used to separate DNT cell from human peripheral blood. Human pancreatic tumor models were established via implanting BXPC-3 cells into nude mice, and then mice were randomly divided mice into 3 groups, blank group, gemcitabine group and DNT group. Mice weights and mice tumor volumes were measured every 5 days. After 40 days mice were euthanized at cervical dislocation method. Tumor weights were measured. Relative tumor volume and tumor inhibition rate were calculated. Western blot and qPCR were used to detect the expressions of NKG2D and MICA in the transplanted tumors of the three groups. Results: The blank group tumor volume and weight of blank group were significantly larger than those of gemcitabine group and DNT group (858.7±35.7 mg, 251.1±19.7 mg, 278.5±17.3 mg, P<0.001), but there were no significantly difference between DNT group and gemcitabine group. The tumor inhibition rate of gemcitabine and DNT cell were 40.4% and 35.5%. Western blot and qPCR showed that MICA mRNA and protein levels in blank group were significantly higher than those in DNT group (P=0.001, P=0.003). NKG2D mRNA and protein levels in blank group were significantly lower than those in DNT cells group (P<0.001, P=0.001). Conclusion: DNT cell can significantly inhibit the growth of pancreatic carcinoma in vivo, and the mechanism may be involved in abnormal expressions of MICA and NKG2D.

"Bitter-Sweet" Polymeric Micelles Formed by Block Copolymers from Glucosamine and Cholic Acid

Natural compounds glucosamine and cholic acid have been used to make acrylic monomers which are subsequently used to prepare amphiphilic block copolymers by reversible addition-fragmentation chain transfer (RAFT) polymerization. Despite the striking difference in polarity and solubility, three diblock copolymers consisting of glucosamine and cholic acid pendants with different hydrophilic and hydrophobic chain lengths have been synthesized without the use of protecting groups. They are shown to self-assemble into polymeric micelles with a "bitter" bile acid core and "sweet" sugar shell in aqueous solutions, as evidenced by dynamic light scattering and transmission electron microscopy. The critical micelle concentration varies with the hydrophobic/hydrophilic ratio, ranging from 0.62 to 1.31 mg/L. Longer chains of polymers induced the formation of larger micelles in range of 50-70 nm. These micelles can solubilize hydrophobic compounds such as Nile Red in aqueous solutions. Their loading capacity mainly depends upon the hydrophobic/hydrophilic ratio of the polymers, and may be also related to the length of the hydrophilic block. These polymeric micelles allowed for a 10-fold increase in the aqueous solubility of paclitaxel and showed no cytotoxicity below the concentration of 500 mg/L. Such properties make these polymeric micelles interesting reservoirs for hydrophobic molecules and drugs for biomedical applications.

Self-Assembly of a Bile Acid Dimer in Aqueous Solutions: From Nanofibers to Nematic Hydrogels

A mixture of a cholic acid dimer with a secondary amine group and formic acid at a molar ratio of 1/1 is regarded as an organic salt, and it self-assembles in aqueous solutions to form monodisperse nanofibers. The nanofibers are separated at low concentrations of the mixture but entangle with each other at high concentrations to form well-dispersed and randomly arranged 3D fibrous networks. Above the minimum gelation concentration of the dimer, the fibrous network is strong enough to gelate the aqueous solutions to form a hydrogel. Hydrogels obtained from the dimer salt at a lower concentration are isotropic and show extinction between crossed polarizers in the polarizing microscope, whereas they become anisotropic (i.e., nematic hydrogels) upon increasing the dimer salt concentration or under physical stirring. The parallel arrangement of nanofibers from randomly directed fibrous networks may be responsible for the formation of such nematic hydrogels.

Oxygen Inhibition in Dental Resins

Oxygen inhibits free radical polymerization and yields polymers with uncured surfaces. This is a concern when thin layers of resin are being polymerized, or in circumstances where conventional means of eliminating inhibition are inappropriate. In this study, we tested the hypothesis that viscosity, filler content, and polymerization temperature modify oxygen diffusion in the resin or the reactivity of radical species, and affect the degree of conversion near the surface. Confocal Raman micro-spectroscopy was used to measure monomer conversion from the surface to the bulk of cured resins. Increased viscosity was shown to limit oxygen diffusion and increase conversion near the surface, without necessarily modifying the depth of inhibition. The filler material was shown to increase, simultaneously, oxygen diffusivity and the viscosity of the resin, which have opposite effects on conversion. Polymerization at a temperature above ~ 110°C was shown to eliminate oxygen inhibition.

Facile Assembly of Large-Area 2D Microgel Colloidal Crystals Using Charge-Reversible Substrates

2D colloidal crystals (CCs) have important applications; however, the fabrication of large-area, high-quality 2D CCs is still far from being trivial, and the fabrication of 2D microgel CCs is even harder. Here, we have demonstrated that they can be facilely fabricated using charge-reversible substrates. The charge-reversible substrates were prepared by modification with amino groups. The amino groups were then protected by amidation with 2,2-dimethylsuccinic anhydride. At acidic pH, the surface charge of the modified substrate will change from negative to positive as a result of the hydrolysis of the amide bonds and the regeneration of the amino groups. 2D microgel CCs can be simply fabricated by applying a concentrated microgel dispersion on the modified substrate. The negatively charged surface of the substrate allows the negatively charged microgel spheres, especially those close to the substrate, to self-assemble into 3D CCs. With the gradual hydrolysis of the amide bonds and the charge reversal of the substrate, the first 111 plane of the 3D assembly is fixed in situ on the substrate. The resulting 2D CC has a high degree of ordering because of the high quality of the parent 3D microgel CC. Because large-area 3D microgel CCs can be facilely fabricated, this method allows for the fabrication of 2D CCs of any size. Nonplanar substrates can also be used. In addition, the interparticle distance of the 2D array can be tuned by the concentration of the microgel dispersion. Besides rigid substrates (such as glass slides, quartz slides, and silicon wafers), flexible polymer films, including polyethylene terephthalate and poly(vinyl chloride) films, were also successfully used as substrates for the fabrication of 2D microgel CCs.

Successful cloning of an adult breeding boar from the novel Chinese Guike No. 1 swine specialized strain

Somatic cloning, also known as somatic cell nuclear transfer (SCNT), is a promising technology which has been expected to rapidly extend the population of elaborately selected breeding boars with superior production performance. Chinese Guike No. 1 pig breed is a novel swine specialized strain incorporated with the pedigree background of Duroc and Chinese Luchuan pig breeds, thus inherits an excellent production performance. The present study was conducted to establish somatic cloning procedures of adult breeding boars from the Chinese Guike No. 1 specialized strain. Ear skin fibroblasts were first isolated from a three-year-old Chinese Guike No. 1 breeding boar, and following that, used as donor cell to produce nuclear transfer embryos. Such cloned embryos showed full in vitro development and with the blastocyst formation rate of 18.4 % (37/201, three independent replicates). Finally, after transferring of 1187 nuclear transfer derived embryos to four surrogate recipients, six live piglets with normal health and development were produced. The overall cloning efficiency was 0.5 % and the clonal provenance of such SCNT derived piglets was confirmed by DNA microsatellite analysis. All of the cloned piglets were clinically healthy and had a normal weight at 1 month of age. Collectively, the first successful cloning of an adult Chinese Guike No. 1 breeding boar may lay the foundation for future improving the pig production industry.

Self-Healing Supramolecular Hydrogels Based on Reversible Physical Interactions

Dynamic and reversible polymer networks capable of self-healing, i.e., restoring their mechanical properties after deformation and failure, are gaining increasing research interest, as there is a continuous need towards extending the lifetime and improving the safety and performance of materials particularly in biomedical applications. Hydrogels are versatile materials that may allow self-healing through a variety of covalent and non-covalent bonding strategies. The structural recovery of physical gels has long been a topic of interest in soft materials physics and various supramolecular interactions can induce this kind of recovery. This review highlights the non-covalent strategies of building self-repairing hydrogels and the characterization of their mechanical properties. Potential applications and future prospects of these materials are also discussed.

Thermo- and pH-Responsive Copolymers Bearing Cholic Acid and Oligo(ethylene glycol) Pendants: Self-Assembly and pH-Controlled Release

A family of block and random copolymers of norbornene derivatives bearing cholic acid and oligo(ethylene glycol) pendants were prepared in the presence of Grubbs' catalyst. The phase transition temperature of the copolymers in aqueous solutions may be tuned by the variation of comonomer ratios and pH values. Both types of copolymers formed micellar nanostructures with a hydrophilic poly(ethylene glycol) shell and a hydrophobic core containing cholic acid residues. The micellar size increased gradually with increasing pH due to the deprotonation of the carboxylic acid groups. These micelles were capable of encapsulating hydrophobic compounds such as Nile Red (NR). A higher hydrophobicity/hydrophilicity ratio in both copolymers resulted in a higher loading capacity for NR. With similar molecular weights and monomer compositions, the block copolymers showed a higher loading capacity for NR than the random copolymers. The NR-loaded micelles exhibited a pH-triggered release behavior. At pH 7.4 within 96 h, the micelles formed by the block and random of copolymers released 56 and 97% NR, respectively. Therefore, these micelles may have promise for use as therapeutic nanocarriers in drug delivery systems.

Glucosamine-Anchored Graphene Oxide Nanosheets: Fabrication, Ultraviolet Irradiation, and Electrochemical Properties

A biofunctionalized graphene oxide (GO) nanosheet with improved physicochemical properties is useful for electrocatalysis and sensor development. Herein, a new class of functionalized GO with a chemically anchored biomolecule glucosamine is developed. Structural and chemical analyses confirm the glucosamine anchoring. Ultraviolet irradiation transforms the surface chemistry of GO. Glucosamine-anchored GO nanosheets exhibit improved cyclic voltammetric and amperometric sensing activity toward the model redox probe, ruthenium(II) and N-acetylneuraminic acid, respectively. The biomolecular anchoring and ultraviolet irradiation helped to tune and enhance the properties of GO, which may find multiple applications in optimizing sensor platforms.

Swelling-induced surface instability patterns guided by pre-introduced structures

Swelling-induced, spontaneously generated surface instability patterns in substrate-attached hydrogel films can be harnessed for advanced applications, however, methods to control their formation and morphology are missing. Here we propose that their generation may be guided by intentionally pre-introduced line structures. While uniform gel films produce irregular polygonal instability patterns, instability patterns generated in pre-patterned films with hexagonal line structures are regular hexagons with long-range order. The pre-introduced line structures act as defects in the generation of the surface instability patterns, which determine the position of the creases, regulate their rearrangement and determine their final morphology. The contrast between the pre-introduced structures and the surrounding area should be high enough for the pre-introduced structures to act as defects. Only when the characteristic wavelength of the pre-introduced pattern matches with the one of the gel film, perfect hexagonal patterns can be obtained. The gel films with uniform topographic features may find various advanced applications.

Thermoresponsiveness of copolymers bearing cholic acid pendants induced by complexation with β-cyclodextrin

Copolymers of N-alkylacrylamides and methacrylate bearing cholic acid pendant groups were synthesized via radical polymerization. The cholic acid pendant groups of such copolymers can form complexes with β-cyclodextrin, and the effect of complexation on their thermoresponsive properties was studied. The phase transition temperatures (transition from hydrophilic to hydrophobic state) of the copolymers gradually increase with the addition of β-cyclodextrin, due to the complexation of the cholic acid guest with the β-cyclodextrin host. The increase of the phase transition temperature may be reversed by the addition of a competing guest molecule, potassium 1-adamantylcarboxylate. The host-guest complexation provides a straightforward way to vary the thermoresponsive properties of such copolymers.

Invertible vesicles and micelles formed by dually-responsive diblock random copolymers in aqueous solutions

Dually responsive diblock random copolymers poly(nPA0.8-co-DEAEMA0.2)-block-poly(nPA0.8-co-EA0.2) were made from N-n-propylacrylamide (nPA), 2-(diethylamino)ethyl methacrylate (DEAEMA) and N-ethylacrylamide (EA) via reversible addition-fragmentation chain transfer (RAFT) polymerization. Copolymers of different block length ratios, poly(nPA28-co-DEAEMA7)-block-poly(nPA29-co-EA7) (P1) and poly(nPA28-co-DEAEMA7)-block-poly(nPA70-co-EA18) (P2), self-assemble into vesicles and micelles, responding to external stimuli in aqueous solutions, and both show "schizophrenic" inversion behavior when the pH and temperature are varied. The relative lengths of the two blocks are shown to affect the self-assembly of amphiphilic diblock copolymers. P1 has a similar length for both blocks and forms spherical vesicles with the first block poly(nPA29-co-EA7) as the membrane inner layer at pH 7 and 37 °C (above the cloud point of the more hydrophobic block, CP1), while spherical micelle-like aggregates are obtained at pH 10 and 25 °C (above CP1) with the second block poly(nPA28-co-DEAEMA7) as the core. In comparison, P2 has a different block length ratio (1 : 3, thus a much longer second block) and forms spherical micelles above CP1 at both pH 7 (the second block as the core) and pH 10 (the first block as the core). Further aggregation was observed by heating the polymer solution above the cloud point of the more hydrophilic block (CP2). The variation of the length and chemical composition of the blocks allows the tuning of the responsiveness of the block copolymers toward both pH and temperature and determines the formation of either micelles or vesicles during the aggregation.

Block and random copolymers bearing cholic acid and oligo(ethylene glycol) pendant groups: aggregation, thermosensitivity, and drug loading

A series of block and random copolymers consisting of oligo(ethylene glycol) and cholic acid pendant groups were synthesized via ring-opening metathesis polymerization of their norbornene derivatives. These block and random copolymers were designed to have similar molecular weights and comonomer ratios; both types of copolymers showed thermosensitivity in aqueous solutions with similar cloud points. The copolymers self-assembled into micelles in water as shown by dynamic light scattering and transmission electron microscopy. The hydrodynamic diameter of the micelles formed by the block copolymer is much larger and exhibited a broad and gradual shrinkage from 20 to 54 °C below its cloud point, while the micelles formed by the random copolymers are smaller in size but exhibited some swelling in the same temperature range. Based on in vitro drug release studies, 78% and 24% paclitaxel (PTX) were released in 24 h from micelles self-assembled by the block and random copolymers, respectively. PTX-loaded micelles formed by the block and random copolymers exhibited apparent antitumor efficacy toward the ovarian cancer cells with a particularly low half-maximal inhibitory concentration (IC50) of 27.4 and 40.2 ng/mL, respectively. Cholic acid-based micelles show promise as a versatile and potent platform for cancer chemotherapy.

Switchable vesicles formed by diblock random copolymers with tunable pH- and thermo-responsiveness

The thermo-responsiveness of polymers in aqueous media can be tuned by the choice of comonomers used in the synthesis of block copolymers made of random sequences of the same comonomers but of different molar ratios. The same synthetic approach may be applied to other stimuli and we have made diblock random copolymers with both pH- and thermo-responsiveness and studied the formation of vesicles whose membrane core and coronas may be inverted in aqueous media. Sequential reversible addition-fragmentation chain transfer (RAFT) polymerization was used to prepare well-defined block copolymers in the form of AnBm-b-ApCq, where A, B, and C are N-n-propylacrylamide (nPA), 2-(diethylamino)ethyl methacrylate (DEAEMA), and N-ethylacrylamide (EA), respectively. This polymer shows interesting "schizophrenic" behavior in aqueous solutions. Both blocks are thermo-responsive, and one block is pH-responsive in which the tertiary amine group of DEAEMA may be protonated at a lower pH. A molecularly dissolved polymer is obtained at neutral pH and ambient temperature. At pH 7 and 37 °C, the polymer self-assembles into vesicles with the poly(nPA0.8-co-EA0.2) block as the membrane core (mean hydrodynamic diameter of the vesicles Dh = 148 nm). In an alkaline medium (pH 10) at 25 °C, the membrane core and the coronas of the vesicles are inverted with poly(nPA0.8-co-DEAEMA0.2) block forming the core (Dh = 60 nm). In addition, two-step phase transitions are observed in both alkaline and neutral solutions corresponding to the cloud points of the individual blocks. Here, the random nature of the blocks allows fine-tuning the thermo-responsiveness based solely on lower critical solution temperatures and its combination with pH-sensitivity provides vesicles with switchable membrane core and corona in aqueous solution.

Aggregation behavior of pegylated bile acid derivatives

Bile acids are amphiphilic endogenous steroids that act as anionic surfactants in the digestive tract and aggregate in aqueous solutions. Nonionic surfactants were synthesized by grafting poly(ethylene glycol) chains of various lengths (pegylation) to three bile acids (lithocholic, deoxycholic, and cholic acid) using anionic polymerization. The aggregation properties of the derivatives were studied with viscosity measurements and light scattering as well as with steady-state and time-resolved fluorescence techniques, and the aggregates were visualized by transmission electron microscopy to elucidate the effect of pegylation on the aggregation process. The fluorescence results showed a good correlation with the capacity of the bile acid derivatives to solubilize a hydrophobic drug molecule. The solubilization of ibuprofen depends on the length and the number of grafted PEG chains, and the solubilization efficiency increases with fewer PEG chains on the bile acid. The results indicate their potential for use in the design of new bile acid-based drug-delivery systems.

Fractal structures of the hydrogels formed in situ from poly(N-isopropylacrylamide) microgel dispersions

Dispersions of poly(N-isopropylacrylamide) (PNIPAM) microgel thermally gel in the presence of inorganic salts. The in situ-formed hydrogels, with a network of soft particles, represent a new type of colloidal gels. Here, their fractal structures were determined by rheological measurements, using the models of both Shih et al. and Wu and Morbidelli. According to the definition of Shih et al., the colloidal PNIPAM gels fall into the strong-link regime. Yet the calculated fractal dimension of the floc backbone, x, yielded unrealistic negative values, suggesting this model is inapplicable for the present system. The Wu-Morbidelli model gives physically sounder results. According to this model, the strengths of the inter- and intrafloc links are comparable, and the in situ-formed gels are in the transition regime. The fractal dimension, d(f), of the hydrogel decreases from ∼2.5 to ∼1.8 when the heating temperature increases from 34 to 40 °C. The d(f) values suggest different aggregation mechanisms at different temperatures, that is, a reaction-limited one accompanied by rearrangement at low temperature, a typical reaction-limited one at the intermediate temperature, and a diffusion-limited one at high temperature. With increasing salt concentration, the d(f) of the hydrogel decreases from ∼2.1 to ∼1.7, suggesting the aggregation mechanism changes from reaction-limited to diffusion-limited. The effects of both temperature and salt concentration can be explained by the changes in the interactions among the microgel particles. The thermogellable PNIPAM microgel dispersions may serve as a model system for the study of heat-induced gelation of globular proteins.

Multi-responsive properties of a poly(ethylene glycol)-grafted alternating copolymers of distyrenic monomer with maleic anhydride

A series of amphiphilic copolymers were synthesized by reversible addition-fragmentation chain transfer cyclocopolymerization of a styrenic monomer with maleic anhydride followed by grafting methoxy poly(ethylene glycol) onto the anhydride groups of the polymer chain. These amphiphilic graft copolymers exhibit multiple responsiveness toward temperature, pH, and selected cations in aqueous solutions. The cloud points (CP) of the graft copolymers increase with increasing length of the side chains and with increasing pH value of the solution. The addition of KCl and LiCl to the solutions had a salting-out effect lowering the CPs of the graft copolymers. The addition of NaCl, however, first raised the CP due to the complexation of the crown ether with Na(+) and then lowered the CP. The light scattering results confirmed an increase in phase transition temperature at lower concentrations of NaCl (5 and 10 mM) and then a decrease at a higher concentration of the sodium salt (100 mM).

Aggregation and thermoresponsive properties of new star block copolymers with a cholic acid core

Poly(allyl glycidyl ether) (PAGE) and poly(ethylene glycol) (PEG) blocks were sequentially grown via anionic polymerization to form four block copolymer arms on a cholic acid (CA) core, yielding star block copolymers (CA(AGE(8)-b-EG(n))(4)) with low polydispersities (ca. 1.05). The introduction of PAGE segments into CA(PEG)(4) significantly reduced their crystallinity. The polymers can aggregate in water at room temperature above their critical aggregation concentration. The copolymers are thermoresponsive; their behavior in aqueous solutions was studied by the use of UV-visible spectroscopy, dynamic light scattering, and transmission electron microscopy. Their cloud points vary from 13 to 55 °C with increasing length of the PEG segments. Double thermoresponsive behavior was observed with short PEG segments because of a two-step transition process: small micelles are formed upon heating and then further aggregate into micellar clusters through the association of PEG chains.

NMR imaging of chitosan and carboxymethyl starch tablets: swelling and hydration of the polyelectrolyte complex

The hydration and swelling properties of the tablets made of chitosan, carboxymethyl starch, and a polyelectrolyte complex of these two polysaccharides have been studied by NMR imaging. We studied the effect of pH and ionic strength on the swelling of the tablets and on the diffusion of fluid into the tablets in water and simulated physiological fluids. The pH value of the fluids exerts a more significant effect than their ionic strengths on the swelling of the tablets. The tablets are compared also with those made of cross-linked high amylose starch. The formation of complex helps to keep the integrity of the tablets in various media and render a slow and restricted swelling similar to that of the tablets of the cross-linked high amylase starch, which is significantly lower than the swelling of chitosan and of carboxymethyl starch. The capacities to modulate the release rate of drugs in different media are discussed by comparing the matrices and evaluating the preparation process of the complex. A sustained release of less soluble drugs such as aspirin in gastrointestinal fluids can be provided by the complex, due to the ionic interaction and hydrogen bonding between the drug and the biopolymer complex.

Thermosensitivity of bile acid-based oligo(ethylene glycol) stars in aqueous solutions

Amphiphilic star-shaped oligo(ethylene glycol)s with a hydrophobic bile acid core and varying number of hydrophilic arms have been made. Their thermal behavior in aqueous solutions depends on the number rather than the length of the arms. The two-armed lithocholate derivative showed the strongest tendency for association and exhibited the lowest cloud point (79 °C) of the oligomers made, as well as another phase separation at a lower temperature (31 °C). The "double thermosensitivity" arising both from the salt-dependent LCST of the oligo(ethylene glycol) segments and the temperature-responsive self-assembly of amphiphilic bile acid derivative provides an interesting path in the design of bile acid-based smart materials.

1,2,3-Triazole-containing molecular pockets derived from cholic acid: the influence of structure on host-guest coordination properties

Two cholic acid-containing trimers with 1,2,3-triazole groups close to the connecting point ("top") and at the end of the cholic acid arms ("bottom") were synthesized. These molecules are able to form hydrophobic pockets and solubilize pyrene and other hydrophobic molecules in polar media due to the facial amphiphilicity of cholic acid. Heavy metal ions such as Cu(II) can also be coordinated by the 1,2,3-triazole groups, as shown by EPR spectroscopy. Due to the vicinity of metal ions and pyrene in the pockets, the fluorescence of pyrene is quenched. However, the position of the 1,2,3-triazole groups has a crucial influence on the metal ion complexation. The trimer with 1,2,3-triazole groups at the top is found to bind metal ions more effectively and gives rise to a significantly enhanced fluorescence quenching efficiency. Here, the metal ions act as one tridentate chelating agent, while the triazoles on the bottom rather behave as single entities without any cooperativity in binding to the metal. In the latter case, the quenching effect is reduced considerably despite the fact that both trimers are able to bind Cu(II). This indicates that the specific and strong binding of Cu(II) at the top leads to closer spatial proximity between metal ion and pyrene when compared to the Cu(II) bound on the bottom.

Role of protein contaminants in the immunogenicity of alginates

Alginate is widely used for cell microencapsulation and transplantation. There is a lack of standardization of alginate purity and composition. In a previous study, we compared different alginate purification methods and concluded that polyphenol and endotoxin contaminants were eliminated efficiently but residual protein contaminants persisted with all of the methods under evaluation. The objective of this study was to test the hypothesis that residual proteins play a role in the immunogenicity of certain alginate preparations. Using preparative size exclusion chromatography (SEC) and a large scale purification protocol that was derived from the findings obtained with SEC, we substantially decreased the protein content of alginate preparations. When implanted into mouse peritoneum, barium alginate beads made of alginates that were purified using SEC or the derived large scale protocol induced significantly less pericapsular cell adhesion than those made with control alginates. In conclusions, these results suggest that removing residual protein contamination may decrease the immunogenicity of certain alginate preparations. The measurement of proteins could be used as a screening method for evaluating alginate preparations.

Functional star polymers with a cholic acid core and their thermosensitive properties

Star polymers derived from cholic acid with poly(allyl glycidyl ether) arms have been prepared via anionic polymerization, yielding polymers with well-defined molecular weight and low polydispersity. The double bonds of the allyl groups on the polymer are used to introduce either amine or carboxylic acid groups to obtain amphiphilic polymers with cationic and anionic groups, respectively. The polymers can aggregate in water above a certain critical concentration, which was found to vary with the arm length of the star polymers. The star polymers bearing amino groups showed interesting thermosensitivity, which also depends on the pH of the media. A simple acetylation of the amine groups can sharpen the transition and vary the cloud point from 15 to 48 degrees C, depending on the degree of acetylation. Such polymers offer useful alternatives to the existing thermosensitive polymers.

Molecular pockets derived from cholic acid as chemosensors for metal ions

Molecular pockets in the form of a tripod made of cholic acid were found to be able to solubilize pyrene in polar media as a result of the facial amphiphilicity of bile acids. The trimer containing 1,2,3-triazole groups can complex with heavy metal ions, as clearly shown by electron paramagnetic resonance spectroscopy. Both the metal cation and the pyrene molecule can be brought close together in the cavity formed by the cholic acid trimer, resulting in significantly improved efficiency for fluorescence quenching of pyrene. The decrease of fluorescence intensity can be used for the detection of heavy metal ions, and the detection limit is about 1 microM in water, suggesting the usefulness of such molecules as chemosensors for such metal ions. A different trimer without the coordinating triazole groups is shown to shield pyrene away from metal ions, causing a much reduced fluorescence quenching.

Invertible amphiphilic molecular pockets made of cholic acid

A trimer of cholic acid was prepared via a simple isocyanate linkage. Fluorescence and UV-vis spectroscopic studies showed that the same cholane trimer can form either a hydrophobic cavity in aqueous solutions or a hydrophilic cavity in an apolar solvent using pyrene and a derivative of pyrene as probes. The dynamic inversion of the cavities was demonstrated for the first time by a simple change of the polarity of the solvent media by adjusting from an aqueous buffer to tetrahydrofuran and vice versa. The NMR study of a dimer model compound of cholic acid indicated a restricted conformation exist in the solvent mixture of chloroform and methanol.

New dental composites containing multimethacrylate derivatives of bile acids: a comparative study with commercial monomers

We have prepared multifunctional methacrylate derivatives of bile acids as cross-linkable monomers for use in dental composites. By modifying the chemical structure of the monomers, we were able to vary the viscosity, hydrophobicity, and reactivity and have studied the effect of these parameters on the conversion of the monomers, the shrinkage during polymerization, and the mechanical properties of the resulting polymers and composites. Materials containing these new monomers generally had physical, thermal, and mechanical properties comparable to those containing the commonly used dental monomers BisGMA or UDMA and had lower polymerization shrinkage. The multimethacrylate derivatives of cholic acid, which are known to be less cytotoxic than BisGMA and UDMA, are shown to be promising materials for dental applications.