Identification of calcium chelating peptides from peanut protein hydrolysate and absorption activity of peptide-calcium complex.

BACKGROUND: Peanut peptides have good chelating ability with metal ions. However, there are few studies on the chelation mechanism of peanut peptides with calcium and absorption properties of peptide-calcium complex. RESULTS: Peptides with high calcium chelating rate were isolated and purified from peanut protein hydrolysate (PPH), and the chelation rate of component F21 was higher (81.4 ± 0.8%). Six peptides were identified from component F21 by liquid chromatography-tandem mass spectrometry, and the frequency of acidic amino acids and arginine in the amino acid sequence was higher in all six peptides. Peanut peptide-calcium complex (PPH21-Ca) was prepared by selecting component F21 (PPH21). Ultraviolet analysis indicated that the chelate reaction occurred between peanut peptide and calcium ions. Fourier transform infrared analysis showed that the chelating sites were carboxyl and amino groups on the amino acid residues of peptides. Scanning electron microscopy revealed that the surface of peanut peptide had a smooth block structure, but the surface of the complex had a granular morphology. Caco-2 cell model tests revealed that the bioavailability of PPH21-Ca was 58.4 ± 0.5%, which was significantly higher than that of inorganic calcium at 37.0 ± 0.4%. CONCLUSION: Peanut peptides can chelate calcium ions by carboxyl and amino groups, and the peptide-calcium complex had higher bioavailability. This study provides a theoretical basis for the development of new calcium supplement products that are absorbed easily. © 2024 Society of Chemical Industry.

Bacterial Biofilm Formation on Biomaterials and Approaches to Its Treatment and Prevention.

Bacterial biofilms can cause widespread infection. In addition to causing urinary tract infections and pulmonary infections in patients with cystic fibrosis, biofilms can help microorganisms adhere to the surfaces of various medical devices, causing biofilm-associated infections on the surfaces of biomaterials such as venous ducts, joint prostheses, mechanical heart valves, and catheters. Biofilms provide a protective barrier for bacteria and provide resistance to antimicrobial agents, which increases the morbidity and mortality of patients. This review summarizes biofilm formation processes and resistance mechanisms, as well as the main features of clinically persistent infections caused by biofilms. Considering the various infections caused by clinical medical devices, we introduce two main methods to prevent and treat biomaterial-related biofilm infection: antibacterial coatings and the surface modification of biomaterials. Antibacterial coatings depend on the covalent immobilization of antimicrobial agents on the coating surface and drug release to prevent and combat infection, while the surface modification of biomaterials affects the adhesion behavior of cells on the surfaces of implants and the subsequent biofilm formation process by altering the physical and chemical properties of the implant material surface. The advantages of each strategy in terms of their antibacterial effect, biocompatibility, limitations, and application prospects are analyzed, providing ideas and research directions for the development of novel biofilm infection strategies related to therapeutic materials.

Treatment of Pseudomonas aeruginosa infectious biofilms: Challenges and strategies.

Pseudomonas aeruginosa, a Gram-negative bacterium, is one of the major pathogens implicated in human opportunistic infection and a common cause of clinically persistent infections such as cystic fibrosis, urinary tract infections, and burn infections. The main reason for the persistence of P. aeruginosa infections is due to the ability of P. aeruginosa to secrete extracellular polymeric substances such as exopolysaccharides, matrix proteins, and extracellular DNA during invasion. These substances adhere to and wrap around bacterial cells to form a biofilm. Biofilm formation leads to multiple antibiotic resistance in P. aeruginosa, posing a significant challenge to conventional single antibiotic therapeutic approaches. It has therefore become particularly important to develop anti-biofilm drugs. In recent years, a number of new alternative drugs have been developed to treat P. aeruginosa infectious biofilms, including antimicrobial peptides, quorum-sensing inhibitors, bacteriophage therapy, and antimicrobial photodynamic therapy. This article briefly introduces the process and regulation of P. aeruginosa biofilm formation and reviews several developed anti-biofilm treatment technologies to provide new directions for the treatment of P. aeruginosa biofilm infection.

Effect of plant tannin and glycerol on thermoplastic starch: Mechanical, structural, antimicrobial and biodegradable properties.

Thermoplastic starch is a good candidate for preparing biobased plastics. However, certain deficiencies in the ingredient, such as its poor mechanical strength and lack of antibacterial activity, need to be strengthened. In this work, a new method of producing TPS via extrusion and injection at a large scale was explored using tannin and glycerol simultaneously. The effect of the tannin content on the performance of TPS was investigated. The results showed that the synergistic effect of a small amount of tannin (2.5-7.5 wt%) and glycerol increased the tensile strength and maintained a stable elongation at break, and tannin aggregation occurred in TPS at higher tannin contents, which corresponded to increased tensile and flexural strengths. 15T-TPS has optimal mechanical performance with maximal relative crystallinity. The introduced tannin in TPS effectively enhanced the thermal stability but slightly reduced the biodegradability in soil and endowed TPS with antibacterial activity. Therefore, TPS containing tannins has the potential to be used in biomedical, food packaging and agricultural areas.

Strategies for Zinc Uptake in Pseudomonas aeruginosa at the Host-Pathogen Interface.

As a structural, catalytic, and signaling component, zinc is necessary for the growth and development of plants, animals, and microorganisms. Zinc is also essential for the growth of pathogenic microorganisms and is involved in their metabolism as well as the regulation of various virulence factors. Additionally, zinc is necessary for infection and colonization of pathogenic microorganisms in the host. Upon infection in healthy organisms, the host sequesters zinc both intracellularly and extracellularly to enhance the immune response and prevent the proliferation and infection of the pathogen. Intracellularly, the host manipulates zinc levels through Zrt/Irt-like protein (ZIP)/ZnT family proteins and various zinc storage proteins. Extracellularly, members of the S100 protein family, such as calgranulin C, sequester zinc to inhibit microbial growth. In the face of these nutritional limitations, bacteria rely on an efficient zinc transport system to maintain zinc supplementation for proliferation and disruption of the host defense system to establish infection. Here, we summarize the strategies for zinc uptake in conditional pathogenic Pseudomonas aeruginosa, including known zinc uptake systems (ZnuABC, HmtA, and ZrmABCD) and the zinc uptake regulator (Zur). In addition, other potential zinc uptake pathways were analyzed. This review systematically summarizes the process of zinc uptake by P. aeruginosa to provide guidance for the development of new drug targets.

Preparation and Properties of Corn Starch/Chitin Composite Films Cross-Linked by Maleic Anhydride.

To improve the functional properties of starch-based films, chitin (CH) was prepared from shrimp shell powder and incorporated into corn starch (CS) matrix. Before blending, maleic anhydride (MA) was introduced as a cross-linker. Composite CS/MA-CH films were obtained by casting-evaporation approach. Mechanical property estimation showed that addition of 0-7 wt % MA-CH improved the tensile strength of starch films from 3.89 MPa to 9.32 MPa. Elongation at break of the films decreased with the addition of MA-CH, but the decrease was obviously reduced than previous studies. Morphology analysis revealed that MA-CH homogeneously dispersed in starch matrix and no cracks were found in the CS/MA-CH films. Incorporation of MA-CH decreased the water vapor permeability of starch films. The water uptake of the films was reduced when the dosage of MA-CH was below 5 wt %. Water contact angles of the starch films increased from 22° to 86° with 9 wt % MA-CH incorporation. Besides, the composite films showed better inhibition effect against Escherichia coli and Staphylococcus aureus than pure starch films.

Bio-Based Thermoplastic Starch Composites Reinforced by Dialdehyde Lignocellulose.

In order to improve the mechanical properties and water resistance of thermoplastic starch (TPS), a novel reinforcement of dialdehyde lignocellulose (DLC) was prepared via the oxidation of lignocellulose (LC) using sodium periodate. Then, the DLC-reinforced TPS composites were prepared by an extrusion and injection process using glycerol as a plasticizer. The DLC and LC were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the effects of DLC content on the properties of the DLC/TPS composites were investigated via the evaluation of SEM images, mechanical properties, thermal stability, and contact angles. XRD showed that the crystallinity of the DLC decreased due to oxidation damage to the LC. SEM showed good dispersion of the DLC in the continuous TPS phase at low amounts of DLC, which related to good mechanical properties. The tensile strength of the DLC/TPS composite reached a maximum at a DLC content of 3 wt.%, while the elongation at break of the DLC/TPS composites increased with increasing DLC content. The DLC/TPS composites had better thermal stability than the neat TPS. As the DLC content increased, the water resistance first increased, then decreased. The highest tensile strength and elongation at break reached 5.26 MPa and 111.25%, respectively, and the highest contact angle was about 90.7°.

Surface cross-linked thermoplastic starch with different UV wavelengths: mechanical, wettability, hygroscopic and degradation properties.

Here, we report a method to improve the properties of thermoplastic starch (TPS) by surface ultraviolet (UV) cross-linking. TPS sheets were prepared by injection molding and coated with an ethanol solution of photo-initiator TPO (2,4,6-trimethyl benzoyl diphenyl phosphine oxide), then, irradiated by UV with different wavelengths for 15 min. Untreated and irradiated TPS sheets were characterized using tensile and bending tests, impact tests, dynamic mechanical thermal analysis (DMTA) and infrared spectroscopy (FTIR). FTIR spectra showed that UV irradiation can effectively trigger surface cross-linking of TPS sheets. The mechanical and dynamic mechanical properties of the TPS were improved and the optimized properties were obtained by 308 nm UV irradiation. A tensile strength of 4.1 MPa, a bending strength of 2.7 MPa, an impact strength of 96.8 kJ m-2, and the corresponding activation energy of 251.22 kJ mol-1 were obtained. The water contact angle and moisture absorption of the samples were also investigated and the 308 nm UV irradiated sheets have a contact angle of 74°. Moisture absorption rate as a function of the square root of time showed a sigmoid curve including a linear stage which conforms to Fick's second law. The samples irradiated by 308 nm UV had the lowest equilibrium moisture absorption rate M ∞ and the longest time T 0 to enter into the Fick's diffusion stage and the lowest slope K and diffusion coefficient D. All samples displayed biodegradable properties when buried in soil. This method has potential applications for agricultural mulch films, packing and medical film products.

A novel method to produce sustainable biocomposites based on thermoplastic corn-starch reinforced by polyvinyl alcohol fibers.

Adding reinforced fiber or cross-linking agent into thermoplastic starch (TPS) is an effective method to improve its performance. Herein, biodegradable polyvinyl alcohol fiber (PVAF) and sodium hexametaphosphate (SHMP) were not added into TPS directly; the PVAFs were preliminary treated (pre-soaking) by an SHMP solution, and then mixed with starch and glycerol to prepare 2 wt% PVAF/TPS composites through extrusion and injection molding. This process promoted crosslinking action between PVAFs and starch, and as a consequence enhanced the mechanic and dynamic mechanic behavior. The PVAFs with different immersion times were characterized by SEM, FTIR, and WAXD. The results confirmed that the SHMP coating was formed by a chemical bond connection on the surface of the PVAFs, particularly for the PVAFs soaked for 1.5 h, which produced a corresponding PVAF/TPS composite with a maximum tensile strength of 9.18 MPa and an impact strength of 21.29 kJ m-2. The corresponding tensile fractured cross-section images were shown by SEM. The DMA curves indicated that the pre-soaked PVAFs effectively improved the energy storage modulus and transition temperature of composites, and the activation energy of the starch macromolecules reached a maximum of 349.9 kJ mol-1 during the dynamic mechanic process. The contact angle attained a maximum of 66.25°. Compared with TPS, the pre-soaked PVAF-reinforced PVAF/TPS composites had better mechanical properties, good processability through traditional extrusion and injection molding, reduced water wettability, and potential applications for packaging and catering.

Disodium Guanylate Alleviates Acute Hepatic Injury Induced by Carbon Tetrachloride Via Antioxidative Stress and Antiapoptosis In Vivo and In Vitro.

Hepatic injury is one of the most common digestive system diseases worldwide in clinic. Guanylic acid or guanosine monophosphate (GMP) was an important component of nucleotides, which is mainly in the form of sodium salt (disodium guanylate, GMP-Na2 ). However, its effect on hepatic injury has not yet been investigated. This study is to investigate the protective effects of GMP-Na2 on acute hepatic injury induced by carbon tetrachloride (CCl4 ), and to explore its mechanism. The hepatic injury models of mice and HL-7702 cells were induced by CCl4 . The alanine transaminase (ALT), aspartate aminotransferase (AST), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), malondialdehyde (MDA), total antioxidant capacity (T-AOC) were determined by biochemical method. Hematoxylin-eosin staining were used to determine the morphological changes on liver tissue in mice. The mRNA and protein expressions of caspase-3, Bax, and Bcl-2 were detected by RT-PCR and Western blot analysis. Our results show that GMP-Na2 treatment significantly decreased the activities of ALT and AST, and the levels of MDA as well as increased the levels of SOD, GSH-Px, and T-AOC. Importantly, GMP-Na2 effectively enhanced the antiapoptosis function by upregulating Bcl-2 expression and downregulating caspase-3 and Bax expressions in vivo and in vitro. Moreover, the histopathological changes of liver tissue were obviously improved after GMP-Na2 treatment. These findings suggest that GMP-Na2 has protective effects on hepatic injury, and its mechanisms may be associated with antioxidative stress and antiapoptosis.

Polyvinyl Alcohol Microspheres Reinforced Thermoplastic Starch Composites.

We reported a new method to prepare polyvinyl alcohol (PVA)/thermoplastic starch (TPS) composites by using polyvinyl alcohol microspheres (PVAMS). The PVAMS/TPS composites were characterized using tensile test, scanning electron microscopy (SEM), dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA). The results exhibited that adding small amounts of PVAMSs can effectively improve the mechanical strength and toughness of the composites, especially for the 1 wt %PVAMS in TPS matrix, with a tensile strength of 3.5 MPa, an elongation at break at 71.73% and an impact strength of 33.4 kJ/m². Furthermore, the SEM and shift in the tan δ peak (Tα and Tβ) at the maximum value of 69.87 and −36.52 °C indicates that the PVAMS decreased the mobility of the amorphous starch molecules due to the strong intermolecular hydrogen bonds between PVAMS and TPS. The peak temperature of maximum decomposition rate (Tp) of 1 wt % PVAMS/TPS composites increased about 5 °C compared with TPS in TGA curves.