Facile construction of a molecularly imprinted polymer-based electrochemical sensor for the detection of milk amyloid A.

A molecularly imprinted electrochemical sensor for the detection of serum amyloid A (MAA) in milk was established for early diagnosis of subclinical mastitis in dairy cows. The electrochemical sensor was initially constructed using a nanocomposite material (reduced graphene oxide/gold nanoparticles, AuNPs@rGO) to modify the working electrode. The template protein, MAA, was then immobilized using pyrrole as the functional monomer to carry out the electropolymerization. Finally, the template protein was removed to form a molecular imprint film with the capability to qualitatively and quantitatively signaling of MAA. Cyclic voltammetry (CV), differential pulse voltammetry (DPV), and scanning electron microscopy (SEM) were used to characterize the modification process of the molecularly imprinted electrochemical sensors. Under optimized conditions, the sensor shows two well-behaved linear relationships in the MAA concentration range 0.01 to 200 ng/mL. A lower detection limit was estimated to be 5 pg/mL (S/N = 3). Other parameters including the selectivity, reproducibility (RSD 3.2%), and recovery rate (96.1-103%) are all satisfactory. Compared with the traditional methods, detection of MAA to determine the subclinical mastitis of dairy cows can efficiently be diagnosed and hence prevent an outbreak of dairy cow mastitis. The electrochemical sensor can detect MAA more rapidly, sensitively, and inexpensively than the ELISA-based MAA detection. These advantages indicate that the method is promising for early diagnosis of dairy cows.

Nonswellable and Tough Supramolecular Hydrogel Based on Strong Micelle Cross-Linkings.

Because of the difference in osmotic pressure, most tough hydrogels swell under physiological conditions, which seriously weakens their mechanical properties, limiting their applications in biomedicine. Herein, a novel strategy based on strong and high-density micelle cross-linkings is proposed to prepare nonswellable and tough hydrogel. To realize a strong micelle cross-linker, the synergetic effect of hydrophobic and quadruple hydrogen-bonding interactions is employed by introducing an alkyl chain-protected ureido pyrimidinone moiety into a segmented copolymer backbone. The length of the alkyl is the key factor in determining the strength of the hydrophobic interaction, which was carefully tailored to gain micelles with high strength and suitable solubility. A supramolecular hydrogel was formed in situ by simply linking micelle cross-linkers with poly(ethylene glycol) chains. The strong and high-density micelle cross-linkings restrain multiple effective chains outside the micelle from stretching during swelling, and the deformability of micelle cross-linkings disperses the local stress to maintain the network with high cross-linking density upon loading. Therefore, the hydrogel exhibited an outstanding nonswelling behavior under physiological conditions and excellent mechanical properties with a compressive strength of 4 MPa. The rapid in situ gelation also facilitated injection and cell encapsulation. Meanwhile, it also showed good tissue adhesion, cytocompatibility, and suitable degradability. This novel and facile strategy can offer new insights into the exploitation of cross-linkings to prepare nonswellable hydrogels for biomedical applications.

[Effect of PEG-6000 Simulation Drought Stress on Physiological Characteristics of Guangfeng Medicinal Yam Plantlets].

Objective: In order to provide the theoretical basis for the Guangfeng medicinal yam( Dioscorea opposita) in field transplanting, the effect of PEG-6000 simulation drought stress on physiological characteristics of Guangfeng medicinal yam plantlets was studied. Methods: Using the method of spectrophotometer,the content of total chlorophyll,soluble total sugar, soluble protein and praline,as well as the activities of SOD,CAT and POD of Guangfeng medicinal yam plantlets were tested under PEG-6000 treatment. Results: Under PEG-6000 simulated drought stress, with the increasing of drought stress and the extension of stress time, the total chlorophyll content of Guangfeng medicinal yam plantlets continued to decline, the content of total soluble sugar, proline and MDA of Guangfeng medicinal yam plantlets significantly increased, the content of soluble protein and the activities of CAT,POD and SOD of Guangfeng medicinal yam plantlets increased at first and then decreased. Conclusion: This study reveals the changes of physiological indices of Guangfeng medicinal yam plantlets under PEG-6000 simulation drought stress, which indicated that Guangfeng medicinal yam plantlets have certain drought tolerance.

Preparation of long-acting microspheres loaded with octreotide for the treatment of portal hypertensive.

The purpose of this study was to optimize the preparation method of injectable Octreotide microspheres. To explore the correlation between the solvent system and the general properties of microspheres to reduce burst release and enable them to be used for portal hypertension. Octreotide microspheres were prepared by modified double emulsion solution evaporation method after optimizing preparation conditions. The results showed that Octreotide microspheres had a particle size of 57.48 ± 15.24 µm, and the initial release was significantly reduced. In vitro release and in vivo pharmacokinetic data indicated that Octreotide was released stably within 1200 h. The effects on portal vein pressure, liver tissue morphology and other related indexes were observed after administration. As obvious results, injection of Octreotide microspheres could significantly reduce portal vein pressure and reduce the portal vein lumen area in experimental cirrhotic portal hypertensive rats. The optimized Octreotide PLGA microsphere preparation has been proved to have a good effect on PHT in vivo after detecting aminotransferase (AST) and alanine aminotransferase (ALT) activity, liver tissue hydroxyproline (Hyp) content, serum and liver tissue malondialdehyde (MDA) levels, plasma prostacyclin (PGI2) levels, and liver tissue tumor necrosis factor (TNFα) content. In addition, serum and liver tissue superoxide dismutase (SOD) activity and liver tissue glutathione (GSH) content, plasma thromboxane (TXA2), serum nitric oxide (NO), liver tissue nitric oxide synthase (NOS), and plasma and liver tissue endothelin (ET) were significantly increased.

Alginate-poloxamer/silk fibroin hydrogels with covalently and physically cross-linked networks for cartilage tissue engineering.

Poloxamer was grafted onto alginate and the optimally synthesized alginate-poloxamer (ALG-POL) copolymer was combined with silk fibroin (SF) to produce thermosensitive ALG-POL/SF hydrogels with covalently and physically crosslinked networks. The formulated ALG-POL/SF gels were found to be injectable with sol-gel transitions near physiological temperature and pH. Rheological measurements showed that some ALG-POL/SF gels had their elastic modulus of around 5 kPa or higher with large ratio of elastic modulus to viscous modulus, indicative of their mechanically strong feature. The achieved ALG-POL/SF gels exhibited concurrent enhancement in strength and elasticity when compared to the gels built with either ALG-POL or SF alone. The microscopic insight into dry ALG-POL/SF gels validated that they were highly porous with well-interconnected pore characteristics. These ALG-POL/SF gels showed abilities to support the in-growth of seeded chondrocytes while effectively maintaining their chondrogenic phenotype. Results suggest promising attributes of ALG-POL/SF gels as alternative biomaterial for cartilage tissue engineering.

Multi-tubule conduit-filler constructs loaded with gradient-distributed growth factors for neural tissue engineering applications.

Chitosan/silk fibroin/glycerophosphate gels were loaded with nerve growth factor (NGF) and further processed into multi-tubule fillers. NGF was loaded into the fillers in such a way so that a NGF gradient was established longitudinally along the filler length. A type of poly(lactide-co-glycolide)(PLGA)/chitosan(CH) porous conduit was fabricated using a pre-crosslinking method. The filler was fully filled into the lumen of conduits to build multi-tubule conduit-filler constructs that are intended for long-gap peripheral nerve repair. In vitro degradation in a lysozyme-contained medium revealed that constructs had degradation-tolerant features and the optimized multi-tubule filler was capable of maintaining its multi-tubules unblocked for around 10-week. After being degraded for various periods up to 8 weeks, the optimal conduit-filler constructs showed confirmative ability to retain their compressive load, deformation recovery and tensile strength at about 80N/m, 75% and 15N/cm2 in wet state, respectively. The constructs were able to administer NGF release and to maintain persistent NGF gradients longitudinally distributed inside the PLGA/CH conduit for about 6 weeks or even longer. The PC12 cell neurite extension assay confirmed that the presently developed multi-tubule conduit-filler constructs were reliable for effectively preserving the bioactivity of released NGF.