Pectic-AGP is a major form of Arabidopsis AGPs

As a key component in cell walls of numerous organisms ranging from green algae to higher plants, AGPs play principal roles in many biological processes such as cell-cell adhesion and regulating Ca2+ signaling pathway as a Ca2+-capacitor. Consistently, AGP structures vary from species to species and from tissue to tissue. To understand the functions of AGPs, it is vital to know their structural differences relative to their location in the plant. Thus, AGPs were purified from different Arabidopsis tissues. Analyses of these AGPs demonstrated that the AGPs comprised covalently linked pectin and AGP, referred to as pectic-AGPs. Importantly, these pectic-AGPs were glycosylated with a remarkable variety of polysaccharides including homogalacturonan, rhamnogalacturonan-I, and type II arabinogalactan at different ratios and lengths. This result not only suggests that pectic-AGP is a major form of Arabidopsis AGPs, but also supports AGPs serve as crosslinkers covalently connecting pectins with structures tailored for tissue-specific functions.

Affilin-based retargeting of adenoviral vectors to the epidermal growth factor receptor

INTRODUCTION

Treatment of head and neck squamous cell carcinomas (HNSCC) by oncolytic adenoviral vectors holds promise as an efficient anti-cancer therapy. The epidermal growth factor receptor (EGFR) represents an attractive target receptor since it is frequently overexpressed in many types of HNSCC.

METHODS

To achieve EGFR-specific targeting by human adenovirus type 5 (HAdV-5) based vectors, the EGFR affinity ligand Affilin was covalently attached in a position specific manner either to the fiber or the hexon protein of the vector capsid. In vitro and in vivo studies investigated EGFR-specific cancer cell transduction, susceptibility to natural sequestration mechanisms, pharmacokinetics and biodistribution profiles of Affilin-decorated vectors.

RESULTS

Affilin-decorated vectors showed strongly enhanced and EGFR-specific cancer cell transduction in vitro and less susceptibility to known sequestration mechanisms of HAdV-5 particles. However, in vivo neither systemic nor intratumoral vector administration resulted in an improved transduction of EGFR-positive tumors. Comprehensive analyses indicated hampered EGFR-targeting by Affilin-decorated vectors was caused by rapid vector particle consumption due to binding to the murine EGFR, insufficient tumor vascularization and poor target accessibility for Affilin in the solid tumor caused by a pronounced tumor stroma.

CONCLUSION

In vitro studies yielded proof-of-concept results demonstrating that covalent attachment of a receptor-specific Affilin to the adenoviral capsid provides an effective and versatile tool to address cancer-specific target receptors by adenoviral vectors. Regarding EGFR as the vector target, off-target tissue transduction and low receptor accessibility within the tumor tissue prevented efficient tumor transduction by Affilin-decorated vectors, rendering EGFR a difficult-to-target receptor for adenoviral vectors.

Covalent linkage of bioactive volatiles to a polysaccharide support as a potential approach for preparing active edible coatings and delivery systems for food products

In this study, a potential of covalent linkage approach for developing active edible coatings was examined. Vanillin and trans-cinnamaldehyde were bound to chitosan by Schiff base reaction and reductive amination. The modified polysaccharides were comprehensively characterized and applied as active coatings on fresh-cut melon. The covalent linkage allowed overcoming solubility problems with the lipophilic vanillin and cinnamaldehyde and neutralizing their volatility, producing well-adhered coatings that enhanced fruit quality and storability without sensorial impairment. The attached hydrophobic moieties also provided new polysaccharides with self-assembling ability. Their aggregates were loaded with antimicrobial citral and added to mandarin juice, resulting in up to 6 log CFU/mL microbial count reduction. Thus, the covalent linkage concept offers several advantages, especially when hydrophobic or volatile active agents are used. Further developed, it may become a safe and effective tool for the formation of advanced active edible coatings and delivery vehicles for direct applications on food products.

Polyglycerol mediated covalent construction of magnetic mesoporous silica nanohybrid with aqueous dispersibility for drug delivery

Construction of nanohybrids with chemical and colloidal stability is of great importance for the exploration of their potential applications in biomedical field. In this work, a versatile strategy based on polyglycerol (PG) mediated covalent linkage is developed to fabricate a core-satellite nanohybrid, termed MMSN, consisting of a mesoporous silica nanoparticle (MSN) as a core and many superparamagnetic iron oxide nanoparticles (SPION) on the outer surface. In this synthetic strategy, the PG grafted SPION is derivatized to convert partial periphery hydroxyl groups to carboxyl moieties, followed by attachment to aminated MSN through amide bonds. The PG layer accounting for ~17wt% of MMSN not only serves as a tether to connect the two nanoparticles but also greatly enhances the colloidal stability of the nanohybrid, resulting in no significant change in hydrodynamic diameter and zeta potential during four months. Taking advantage of the combined porosity and magnetic property of the nanohybrid, a photosensitizer chlorin e6 (Ce6) is loaded on MMSN and efficiently delivered into target cells under magnetic guidance, leading to an enhanced efficacy of photodynamic therapy (PDT). The versatile strategy presented here opens up a new route to rational design and fabrication of multifunctional nanohybrids for various biomedical purposes.

Designing Covalently Linked Heterodimeric Four-Helix Bundles

De novo design has proven a powerful methodology for understanding protein folding and function, and for mimicking or even bettering the properties of natural proteins. Extensive progress has been made in the design of helical bundles, simple structural motifs that can be nowadays designed with a high degree of precision. Among helical bundles, the four-helix bundle is widespread in nature, and is involved in numerous and fundamental processes. Representative examples are the carboxylate bridged diiron proteins, which perform a variety of different functions, ranging from reversible dioxygen binding to catalysis of dioxygen-dependent reactions, including epoxidation, desaturation, monohydroxylation, and radical formation. The "Due Ferri" (two-irons; DF) family of proteins is the result of a de novo design approach, aimed to reproduce in minimal four-helix bundle models the properties of the more complex natural diiron proteins, and to address how the amino acid sequence modulates their functions. The results so far obtained point out that asymmetric metal environments are essential to reprogram functions, and to achieve the specificity and selectivity of the natural enzymes. Here, we describe a design method that allows constructing asymmetric four-helix bundles through the covalent heterodimerization of two different α-helical harpins. In particular, starting from the homodimeric DF3 structure, we developed a protocol for covalently linking the two α2 monomers by using the Cu(I) catalyzed azide-alkyne cycloaddition. The protocol was then generalized, in order to include the construction of several linkers, in different protein positions. Our method is fast, low cost, and in principle can be applied to any couple of peptides/proteins we desire to link.

Durable contact active antimicrobial materials formed by a one-step covalent modification of polyvinyl alcohol, cellulose and glass surfaces

In this work we have applied a direct covalent linkage of quaternary ammonium salts (QAS) to prepare a series of contact active antimicrobial surfaces based on widely utilized materials. Formation of antimicrobial polyvinyl alcohol (PVA-QAS), cellulose (cellulose-QAS) and glass (glass-QAS) surfaces was achieved by one step synthesis with no auxiliary linkers. The X-ray photoelectron spectroscopy (XPS) revealed tridentate binding mode of the antimicrobial agent. The antimicrobial activity of the prepared materials was tested on Bacillus cereus, Alicyclobacillus acidoterrestris, Escherichia coli and Pseudomonas aeruginosa. Active site density of the modified materials was examined and found to correlate with their antimicrobial activity. Stability studies at different pH values and temperatures confirmed that the linkage of the bioactive moiety to the surface is robust and resistant to a range of pH and temperatures. Prolonged long-term effectiveness of the contact active materials was demonstrated by their repeated usage, without loss of the antimicrobial efficacy.