Chemical synthesis of polysaccharide-protein and polysaccharide-peptide conjugates: A review

Recent advances in gellan gum production and modification for enhanced applicability in food printing and bioactive delivery applications

The importance of Gellan gum has been increasing gradually and its unique characteristics are suitable for various advanced food technologies. This review outlines recent developments in gellan gum production, modification, and newer applications focusing on food printing and bioactive delivery applications, in the last three years. The yield and production condition of gellan gum is a major factor that affects the cost and its applications. Moreover, modified Gellan gum has been shown to have superior characteristics and functionality as compared to native one. The viscosifying, thermosensitive, gelling etc. characteristics of gellan gum makes it an crucial ingredient in case of preparation of 3D printing ink. Further, gellan gum is also found to be important wall material in case of bioactive delivery application through encapsulation. Optimized methods of production, sustainable feedstock, and stress conditions are critical for the desired functionality and yield of the Gellan gum.

Hyaluronic acid conjugates of glycine peptides and L-tryptophan

This work reports about the conjugation of glycine C-terminal ethyl and methyl ester peptides and L-tryptophan methyl ester with sodium hyaluronate in aqueous solutions using the peptide coupling agent DMTMM (or short DMT, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methyl-morpholinium chloride). Detailed infrared (IR) absorbance and 1H and 13C (2D) NMR studies (heteronuclear multi-bond correlation spectroscopy, HMBC) confirmed covalent and regioselective amide bonds with the D-glucuronate, but also proves the presence of DMT traces in all conjugates. The ethyl ester`s methyl protons on the peptides` C-terminal could be used to quantify the degree of substitution of the peptide on the hyaluronate scaffold by NMR. The ester group also proved stable during conjugation and work-up, and could in some cases be selectively cleaved in water whilst leaving the amide bond intact as shown by potentiometric charge titration, NMR and IR. The conjugates did not influence the capability of human umbilical vein endothelial cells (HUVECs) to reduce MTS (5-[3-(carboxymethoxy)phenyl]-3-(4,5-dimethyl-2-thiazolyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt) to a formazan dye, which points towards a low cytotoxicity for the obtained products. The conjugation method and products could be tested for tissue engineering gels or drug delivery purposes with alternative, biologically active peptides.

Assembly of polysaccharide-based polymer brush for supramolecular hydrogel dressing

Extracted from Platycodon grandiflorum, platycodon grandiflorum polysaccharides (PGPs) with diverse biological functions have been extensively employed for modification and fabrication of hydrogels for biomedical applications, such as wound dressings. However, since the lack of effective structural design, the reported polysaccharide-based hydrogel dressings are still suffered from structural failures and limited bio-functionality. Herein, we demonstrate a facile and general strategy to fabricate a supramolecular hydrogel composed of PGP-based polymer brush as building blocks combined with a Ca2+-mediated self-assembly process. The specific polymer brush with high branch functionality was achieved with polyacrylamide arms evenly grown on the PGP (grafting efficiency as high as 80 %) with series of chemical modifications. With above structural merits, the resulting hydrogel with densely crosslinked polymer brush featured enhanced mechanical strength as well as self-healing, and shear-thinning behaviors. Further biocompatible investigation indicated the as-prepared hydrogels with admirable performances in self-adhesion (adhesive strength of 16.7-79.5 kPa), a pH-responsive swelling ratio as high as 44 at pH 5.4, and pH-responsive degradation. They also showed antioxidant capacity by scavenging DPPH activity of nearly 80 % in 20 min, hemocompatibility, cell viability and cell migration. Impressively, the PGP-based polymer brush hydrogel served as a wound dressing revealed significant acceleration on wound closure.

Threading the needle: Achieving simplicity and performance in cellulose alkanoate ω-carboxyalkanoates for amorphous solid dispersion

Most active pharmaceutical ingredients (APIs) suffer from poor water solubility, often keeping them from reaching patients. To overcome the issues of poor drug solubility and subsequent low bioavailability, amorphous solid dispersions (ASDs) have garnered much attention. Cellulose ester derivatives are of interest for ASD applications as they are benign, sustainable-based, and successful in commercial drug delivery systems, e.g. in osmotic pump systems and as commercial ASD polymers. Synthesis of carboxy-pendant cellulose esters is a challenge, due in part to competing reactions between carboxyls and hydroxyls, forming ester crosslinks. Herein we demonstrate proof-of-concept for a scalable synthetic route to simple, yet highly promising ASD polymers by esterifying cellulose polymers through ring-opening of cyclic succinic or glutaric anhydride. We describe the complexity of such ring-opening reactions, not previously well-described, and report ways to avoid gelation. We report synthesis, characterization, and preliminary in vitro ASD evaluations of fifteen such derivatives. Synthetic routes were designed to accommodate these criteria: no protecting groups, no metal catalysts, mild conditions with standard reagents, simple purification, and one-pot synthesis. Finally, these designed ASD polymers included members that maintained fast-crystallizing felodipine in solution and release it from an ASD at rather high 20 % drug loading (DL).

Dextran Macroinitiator for Synthesis of Polysaccharide-b-Polypeptide Block Copolymers via NCA Ring-Opening Polymerization

Synthesis of polysaccharide-b-polypeptide block copolymers represents an attractive goal because of their promising potential in delivery applications. Inspired by recent breakthroughs in N-carboxyanhydride (NCA) ring-opening polymerization (ROP), we present an efficient approach for preparation of a dextran-based macroinitiator and the subsequent synthesis of dextran-b-polypeptides via NCA ROP. This is an original approach to creating and employing a native polysaccharide macroinitiator for block copolymer synthesis. In this strategy, regioselective (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) oxidation of the sole primary alcohol located at the C-6 position of the monosaccharide at the nonreducing end of linear dextran results in a carboxylic acid. This motif is then transformed into a tetraalkylammonium carboxylate, thereby generating the dextran macroinitiator. This macroinitiator initiates a wide range of NCA monomers and produces dextran-b-polypeptides with a degree of polymerization (DP) of the polypeptide up to 70 in a controlled manner (Đ < 1.3). This strategy offers several distinct advantages, including preservation of the original dextran backbone structure, relatively rapid polymerization, and moisture tolerance. The dextran-b-polypeptides exhibit interesting self-assembly behavior. Their nanostructures have been investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM), and adjustment of the structure of block copolymers allows self-assembly of spherical micelles and worm-like micelles with varied diameters and aspect ratios, revealing a range of diameters from 60 to 160 nm. Moreover, these nanostructures exhibit diverse morphologies, including spherical micelles and worm-like micelles, enabling delivery applications.

Polysaccharide Aldehydes and Ketones: Synthesis and Reactivity

Polysaccharides are biodegradable, abundant, sustainable, and often benign natural polymers. The achievement of selective modification of polysaccharides is important for targeting specific properties and structures and will benefit future development of highly functional, sustainable materials. The synthesis of polysaccharides containing aldehyde or ketone moieties is a promising tool for achieving this goal because of the rich chemistry of aldehyde or ketone groups, including Schiff base formation, nucleophilic addition, and reductive amination. The obtained polysaccharide aldehydes or ketones themselves have rich potential for making useful materials, such as self-healing hydrogels, polysaccharide-protein therapeutic conjugates, or drug delivery vehicles. Herein, we review recent advances in synthesizing polysaccharides containing aldehyde or ketone moieties and briefly introduce their reactivity and corresponding applications.

Reductive amination of oxidized hydroxypropyl cellulose with ω-aminoalkanoic acids as an efficient route to zwitterionic derivatives

Zwitterionic polymers, with their equal amounts of cationic and anionic functional groups, have found widespread utility including as non-fouling coatings, hydrogel materials, stabilizers, antifreeze materials, and drug carriers. Polysaccharide-derived zwitterionic polymers are attractive because of their sustainable origin, potential for lower toxicity, and possible biodegradability, but previous methods for synthesis of zwitterionic polysaccharide derivatives have been limited in terms of flexibility and attainable degree of substitution (DS) of charged entities. We report herein successful design and synthesis of zwitterionic polysaccharide derivatives, in this case based on cellulose, by reductive amination of oxidized 2-hydroxypropyl cellulose (Ox-HPC) with ω-aminoalkanoic acids. Reductive amination products could be readily obtained with DS(cation) (= DS(anion)) up to 1.6. Adduct hydrophilic/hydrophobic balance (amphiphilicity) can be influenced by selecting the appropriate chain length of the ω-aminoalkanoic acid. This strategy is shown to produce a range of amphiphilic, water-soluble, moderately high glass transition temperature (Tg) polysaccharide derivatives in just a couple of efficient steps from commercially available building blocks. The adducts were evaluated as crystallization inhibitors. They are strong inhibitors of crystallization even for the challenging, poorly soluble, fast-crystallizing prostate cancer drug enzalutamide, as supported by surface tension and Flory-Huggins interaction parameter results.

From Nature-Sourced Polysaccharide Particles to Advanced Functional Materials

Polysaccharides constitute over 90% of the carbohydrate mass in nature, which makes them a promising feedstock for manufacturing sustainable materials. Polysaccharide particles (PSPs) are used as effective scavengers, carriers of chemical and biological cargos, and building blocks for the fabrication of macroscopic materials. The biocompatibility and degradability of PSPs are advantageous for their uses as biomaterials with more environmental friendliness. This review highlights the progresses in PSP applications as advanced functional materials, by describing PSP extraction, preparation, and surface functionalization with a variety of functional groups, polymers, nanoparticles, and biologically active species. This review also outlines the fabrication of PSP-derived macroscopic materials, as well as their applications in soft robotics, sensing, scavenging, water harvesting, drug delivery, and bioengineering. The paper is concluded with an outlook providing perspectives in the development and applications of PSP-derived materials.

Effect of Conventional Humid-Dry Heating through the Maillard Reaction on Chemical Changes and Enhancement of In Vitro Bioactivities from Soy Protein Isolate Hydrolysate-Yeast Cell Extract Conjugates

This study investigated the formation of soy protein isolate hydrolysate-yeast cell extract (SPIH-YCE) conjugates through a humid-dry heating process and their impact on bioactivity. The incubation of SPIH-YCE samples at 60 °C and ~75% humidity for varying durations (0, 5, 10, 15, and 20 days) resulted in a significant decrease in reducing sugars and free amino acids, while the degree of glycation increased by approximately 65.72% after 10 days. SDS-PAGE analysis and size exclusion chromatography revealed the presence of peptides and glycoprotein molecules, with an increase in the distribution of larger peptide size chains. The conjugated SPIH-YCE (10 days) exhibited the highest antioxidant capacity compared to the other samples at different incubation times. A comparative study between SPIH-YCE (day 0) and SPIH-YCE after 10 days of incubation showed significantly higher anti-inflammatory and ACE inhibitory activities for the conjugates subjected to the humid-dry heating process. This suggests that SPIH-YCE conjugates could serve as an alternative substance with the potential to provide health benefits by mitigating or preventing non-communicable diseases (NCDs). This research highlights the importance of the Maillard reaction in enhancing bioactivity and offers insights into the alterations of the chemical structure of these conjugates.

Construction of protein-, polysaccharide- and polyphenol-based conjugates as delivery systems

Natural polymers, such as polysaccharides and proteins, have been used to prepare several delivery systems owing to their abundance, bioactivity, and biodegradability. They are usually modified or combined with small molecules to form the delivery systems needed to meet different needs in food systems. This paper reviews the interactions of proteins, polysaccharides, and polyphenols in the bulk phase and discusses the design strategies, coupling techniques, and their applications as conjugates in emulsion delivery systems, including traditional, Pickering, multilayer, and high internal-phase emulsions. Furthermore, it explores the prospects of the application of conjugates in food preservation, food development, and nanocarrier development. Currently, there are seven methods for composite delivery systems including the Maillard reaction, carbodiimide cross-linking, alkali treatment, enzymatic cross-linking, free radical induction, genipin cross-linking, and Schiff base chemical cross-linking to prepare binary and ternary conjugates of proteins, polysaccharides, and polyphenols. To design an effective target complex and its delivery system, it is helpful to understand the physicochemical properties of these biomolecules and their interactions in the bulk phase. This review summarizes the knowledge on the interaction of biological complexes in the bulk phase, preparation methods, and the preparation of stable emulsion delivery system.

An antifouling electrochemical biosensor based on chondroitin sulfate-functionalized polyaniline and DNA-peptide conjugates for cortisol determination in body fluids

An antifouling electrochemical biosensor was constructed based on chondroitin sulfate (CS)-functionalized polyaniline (CS/PANI) and DNA-peptide conjugates that is capable of assaying cortisol directly in human fluids. First, a CS-doped PANI nanocomposite (sensing substrate) was electrodeposited onto a bare glassy carbon electrode to promote electron transport, providing the sensing signal from high peak currents of PANI to improve the sensitivity of the biosensor. Dendritic DNA-peptide conjugates were assembled onto the CS/PANI by exploiting the highly specific and strong interactions between biotin and streptavidin, which amplified the sensing signals toward cortisol. The integration of the DNA-peptide conjugates into the CS/PANI nanocomposite ensured that the biosensor had a synergistic antifouling effect and was capable of detecting cortisol directly in body fluids (sweat, saliva, and tears). When assaying cortisol levels, the biosensor exhibited a linear range over the cortisol concentrations of 1 × 10-12-1 × 10-7 M and a low limit of detection (0.333 × 10-12 M). In the detection of cortisol in real samples, the relative standard deviation (RSD) of the biological samples ranged from 2.94 to 4.23%, and the recovery were calculated to be in the range 95.2-103.2%.

Fabrication of a protein-dextran conjugates formed oral nanoemulsion and its application to deliver the essential oil from Alpinia zerumbet Fructus

The injury of vascular endothelial cells caused by high glucose (HG) is one of the driving factors of vascular complications of diabetes. Oral administration is the most common route of administration for the treatment of diabetes and its vascular complications. Essential oil extracts from Chinese medicine possess potential therapeutic effects on vascular endothelial injury. However, low solubility and volatility of essential oils generally result in poor oral absorption. Development of nanocarriers for essential oils is a promising strategy to overcome the physiological barriers of oral absorption. In this study, a nanoemulsion composed of bovine serum albumin (BSA)-dextran sulfate (DS) conjugate and sodium deoxycholate (SD) was constructed. The nanoemulsions were verified with promoted oral absorption and prolonged circulation time. After the primary evaluation of the nanoemulsion, essential oil from Alpinia zerumbet Fructus (EOFAZ)-loaded nanoemulsion (denoted as EOFAZ@BD5/S) was prepared and characterized. Compared to the free EOFAZ, EOFAZ@BD5/S increased the protective effects on HG-induced HUVEC injury in vitro and ameliorative effects on the vascular endothelium disorder and tunica media fibroelastosis in a T2DM mouse model. Collectively, this study provides a nanoemulsion for the oral delivery of essential oils, which holds strong promise in the treatment of diabetes-induced vascular endothelial injury.

Physical modification of vegetable protein by extrusion and regulation mechanism of polysaccharide on the unique functional properties of extruded vegetable protein: a review

Development and utilization of high quality vegetable protein resources has become a hotspot. Food extrusion as a key technology can efficiently utilize vegetable protein. By changing the extrusion conditions, vegetable protein can obtain unique functional properties, which can meet the different needs of food processing. However, extrusion of single vegetable protein also exposes many disadvantages, such as low degree functional properties, poor quality stability and lower tissue fibrosis. Therefore, addition of polysaccharide has become a new development trend to compensate for the shortcomings of extruded vegetable protein. The unique functional properties of vegetable protein-polysaccharide conjugates (Maillard reaction products) can be achieved after extrusion due to regulation of polysaccharides and adjustment of extrusion parameters. However, the physicochemical changes caused by the intermolecular interactions between protein and polysaccharide during extrusion are complex, so control of these changes is still challenging, and further studies are needed. This review summarizes extrusion modification of vegetable proteins or polysaccharides. Next, the effect of different types of polysaccharides on vegetable proteins and its regulation mechanism during extrusion is mainly introduced, including the extrusion of starch polysaccharide-vegetable protein, and non-starch polysaccharide-vegetable protein. Finally, it also outlines the development perspectives of extruded vegetable protein-polysaccharide.

A Bioresponsive Diselenide-functionalized Hydrogel with Cascade Catalytic Activities for Enhanced Local Starvation- and Hypoxia-Activated Melanoma Therapy

Glutathione (GSH) consumption-enhanced cancer therapies represent important potential cancer treatment strategies. Herein, we developed a new multifunctional diselenide-crosslinked hydrogel with glutathione peroxidase (GPx)-like catalytic activity for GSH depletion-enhanced glucose oxidase (GOx)-mediated tumor starvation and hypoxia-activated chemotherapy. By increasing acid and H₂O₂ during GOx-induced tumor starvation, the degradation of the multiresponsive scaffold could be promoted, which led to accelerated release of the loaded drugs. Meanwhile, the overproduced H₂O₂ led to accelerated intracellular GSH consumption under the cascade catalysis of small molecular selenides released from the degraded hydrogel, further enhancing the curative effect of in situ H₂O₂ and subsequent multimodal cancer treatment. Following the GOx-induced amplification of hypoxia, tirapazamine (TPZ) was transformed into the highly toxic benzotriazinyl radical (BTZ·), exhibiting enhanced antitumor activity. This GSH depletion-augmented cancer treatment strategy effectively boosted GOx-mediated tumor starvation and activated the hypoxia drug, leading to significantly enhanced local anticancer efficacy. STATEMENT OF SIGNIFICANCE: There has been a growing interest in depleting intracellular GSH as a potential strategy for improving ROS-based cancer therapy. Herein, a bioresponsive diselenide-functionalized dextran-based hydrogel with GPx-like catalytic activity was developed for GSH consumption-enhanced local starvation- and hypoxia-activated melanoma therapy. Results showed that the overproduced H₂O₂ led to accelerated intracellular GSH consumption under the cascade catalysis of small molecular selenides released from the degraded hydrogel, further enhancing the curative effect of in situ H₂O₂ and subsequent multimodal cancer treatment.

Synthesis and Characterization of Multi-Reducing-End Polysaccharides

Site-specific modification is a great challenge for polysaccharide scientists. Chemo- and regioselective modification of polysaccharide chains can provide many useful natural-based materials and help us illuminate fundamental structure-property relationships of polysaccharide derivatives. The hemiacetal reducing end of a polysaccharide is in equilibrium with its ring-opened aldehyde form, making it the most uniquely reactive site on the polysaccharide molecule, ideal for regioselective decoration such as imine formation. However, all natural polysaccharides, whether they are branched or not, have only one reducing end per chain, which means that only one aldehyde-reactive substituent can be added. We introduce a new approach to selective functionalization of polysaccharides as an entrée to useful materials, appending multiple reducing ends to each polysaccharide molecule. Herein, we reduce the approach to practice using amide formation. Amine groups on monosaccharides such as glucosamine or galactosamine can react with carboxyl groups of polysaccharides, whether natural uronic acids like alginates, or derivatives with carboxyl-containing substituents such as carboxymethyl cellulose (CMC) or carboxymethyl dextran (CMD). Amide formation is assisted using the coupling agent 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM). By linking the C2 amines of monosaccharides to polysaccharides in this way, a new class of polysaccharide derivatives possessing many reducing ends can be obtained. We refer to this class of derivatives as multi-reducing-end polysaccharides (MREPs). This new family of derivatives creates the potential for designing polysaccharide-based materials with many potential applications, including in hydrogels, block copolymers, prodrugs, and as reactive intermediates for other derivatives.

Fundamental concepts of protein therapeutics and spacing in oncology: an updated comprehensive review

Current treatment regimens in cancer cases cause significant side effects and cannot effectively eradicate the advanced disease. Hence, much effort has been expended over the past years to understand how cancer grows and responds to therapies. Meanwhile, proteins as a type of biopolymers have been under commercial development for over three decades and have been proven to improve the healthcare system as effective medicines for treating many types of progressive disease, such as cancer. Following approving the first recombinant protein therapeutics by FDA (Humulin), there have been a revolution for drawing attention toward protein-based therapeutics (PTs). Since then, the ability to tailor proteins with ideal pharmacokinetics has provided the pharmaceutical industry with an important noble path to discuss the clinical potential of proteins in oncology research. Unlike traditional chemotherapy molecules, PTs actively target cancerous cells by binding to their surface receptors and the other biomarkers particularly associated with tumorous or healthy tissue. This review analyzes the potential and limitations of protein therapeutics (PTs) in the treatment of cancer as well as highlighting the evolving strategies by addressing all possible factors, including pharmacology profile and targeted therapy approaches. This review provides a comprehensive overview of the current state of PTs in oncology, including their pharmacology profile, targeted therapy approaches, and prospects. The reviewed data show that several current and future challenges remain to make PTs a promising and effective anticancer drug, such as safety, immunogenicity, protein stability/degradation, and protein-adjuvant interactions.

Structural characterization and anti-inflammatory activity of a novel polysaccharide PKP2-1 from Polygonatum kingianum

Introduction

This study aimed to investigate the structure characterization and antiinflammatory activity of a novel polysaccharide, PKP2-1, from the rhizomes of Polygonatum kingianum Coll. and Hemsl.

Methods

We isolated a novel polysaccharide, PKP2-1, from the rhizomes of Polygonatum kingianum Coll. and Hemsl. for the first time, which was then successively purified through hot-water extraction, 80% alcohol precipitation, anion exchange and gel permeation chromatography. The in vitro anti-inflammatory activity of PKP2-1 in MH7A cells was assessed using a CCK-8 kit assay.

Results

Monosaccharide composition assay revealed that PKP2-1 was mainly composed of glucose, galactose, mannose, and glucuronic acid at an approximate molar ratio of 6:2:2:1. It had a molecular weight of approximately 17.34 kDa. Structural investigation revealed that the backbone of PKP2-1 consisted of (→2, 3)-α-D-Galp(4→, →2)-α-D-Manp(3→, →2)-β-D-Glcp(4→) and α-D-Glcp(3→) residues with side chains (→2)-β-D-Glcp(4→, →1)-α-D-Galp(4→) and α-D-Glcp(3→) branches located at O-3 position of (→2, 3)-α-D-Galp(4→). The in vitro anti-inflammatory activity of PKP2-1 in MH7A cells revealed that PKP2-1 could reduce the expression of IL-11β and IL-6, increase the expression of IL-10 and induce apoptosis of synovial fibroblasts.

Conclusion

The PKP2-1 could inhibit MH7A cell growth and potentially be exploited as an anti-inflammatory agent.

Aptamers as Smart Ligands for Targeted Drug Delivery in Cancer Therapy

Undesirable side effects and multidrug tolerance are the main holdbacks to the treatment of cancer in conventional chemotherapy. Fortunately, targeted drug delivery can improve the enrichment of drugs at the target site and reduce toxicity to normal tissues and cells. A targeted drug delivery system is usually composed of a nanocarrier and a targeting component. The targeting component is called a "ligand". Aptamers have high target affinity and specificity, which are identified as attractive and promising ligands. Therefore, aptamers have potential application in the development of smart targeting systems. For instance, aptamers are able to efficiently recognize tumor markers such as nucleolin, mucin, and epidermal growth factor receptor (EGFR). Besides, aptamers can also identify glycoproteins on the surface of tumor cells. Thus, the aptamer-mediated targeted drug delivery system has received extensive attention in the application of cancer therapy. This article reviews the application of aptamers as smart ligands for targeted drug delivery in cancer therapy. Special interest is focused on aptamers as smart ligands, aptamer-conjugated nanocarriers, aptamer targeting strategy for tumor microenvironment (TME), and aptamers that are specified to crucial cancer biomarkers for targeted drug delivery.

Boosting physical-mechanical properties of adipic acid/chitosan films by DMTMM cross-linking

In this paper we present a novel strategy to easily prepare biodegradable chitosan derived films as new packaging systems. Combination of chitosan, adipic acid and 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methyl-morpholinium chloride (DMTMM) allowed to obtain high-performing cross-linked films. Biobased glycerol was employed as plasticizer. An in-depth study was performed on ten different samples in order to evaluate the role of DMTMM as cross-linking agent. Experimental data showed that 15 wt% of DMTMM enhanced moisture content and moisture uptake (10.42% and 11.11%), water vapor permeability (0.13 10^-7 g m^-1 h^-1 Pa^-1) and good UV barrier properties. Additionally, 30 wt% of DMTMM significantly increased the tensile strength of films up to 83 MPa and elongation at break values reached 39.7%. Thermogravimetric, IR, XRD and SEM analysis confirmed that physical-mechanical properties of the obtained films were considerably improved, due to cross-linking by DMTMM, demonstrating promising properties for packaging applications.

Regioselective synthesis of polysaccharide-amino acid ester conjugates

Site-specific conjugation of polysaccharides with proteins is very challenging. Creating the ability to control chemo- and regioselective reaction between polysaccharides and amino acid derivatives can not only create potentially useful and bioactive natural polymer constructs, but should also provide useful guidance for the principles of polysaccharide-protein conjugate synthesis. In this work, we exploited regioselective bromination of the non-reducing end primary dextran hydroxyl using N-bromosuccinimide (NBS) and triphenylphosphine (Ph₃P) in the dimethylacetamide (DMAc) and lithium bromide solvent system, thereby enabling a regio- and chemoselective synthetic strategic approach to a variety of polysaccharide-amino acid ester adducts. We demonstrated selective condensation of the α-amino groups of esters of the amino acids tyrosine and proline, displacing the single, terminal C6 bromides of 6-BrDextran, as well as the 6-Br moieties of 6-BrCA320S, with high conversion (71-96%). Histidine ester side group amines were found to react with 6-BrCA320S, while those of tryptophan ester did not. These results provide useful access to polysaccharide-amino acid ester adducts of various architectures, and guide us in designing new pathways to polysaccharide-protein copolymers.

Sources, chemical synthesis, functional improvement and applications of food-derived protein/peptide-saccharide covalent conjugates: a review

Proteins/peptides and saccharides are two kinds of bioactive substances in nature. Recently, increasing attention has been paid in understanding and utilizing covalent interactions between proteins/peptides and saccharides. The products obtained through covalent conjugation of proteins/peptides to saccharides are shown to have enhanced functional attributes, such as better gelling property, thermostability, and water-holding capacity. Additionally, food-derived protein/peptide-saccharide covalent conjugates (PSCCs) also have biological activities, such as antibacterial, antidiabetic, anti-osteoporosis, anti-inflammatory, anti-cancer, immune regulatory, and other activities that are widely used in the functional food industry. Moreover, PSCCs can be used as packaging or delivery materials to improve the bioavailability of bioactive substances, which expands the development of food-derived protein and saccharide resources. Thus, this review was aimed to first summarize the current status of sources, classification structures of natural PSCCs. Second, the methods of chemical synthesis, reaction conditions, characterization and reagent formulations that improve the desired functional characteristics of food-derived PSCCs were introduced. Third, functional properties such as emulsion, edible films/coatings, and delivery of active substance, bio-activities such as antioxidant, anti-osteoporosis, antidiabetic, antimicrobial of food-derived PSCCs were extensively discussed.

Modification of Alginates to Modulate Their Physic-Chemical Properties and Obtain Biomaterials with Different Functional Properties

Modified alginates have a wide range of applications, including in the manufacture of dressings and scaffolds used for regenerative medicine, in systems for selective drug delivery, and as hydrogel materials. This literature review discusses the methods used to modify alginates and obtain materials with new or improved functional properties. It discusses the diverse biological and functional activity of alginates. It presents methods of modification that utilize both natural and synthetic peptides, and describes their influence on the biological properties of the alginates. The success of functionalization depends on the reaction conditions being sufficient to guarantee the desired transformations and provide modified alginates with new desirable properties, but mild enough to prevent degradation of the alginates. This review is a literature description of efficient methods of alginate functionalization using biologically active ligands. Particular attention was paid to methods of alginate functionalization with peptides, because the combination of the properties of alginates and peptides leads to the obtaining of conjugates with properties resulting from both components as well as a completely new, different functionality.