Chemical cross-linking abrogates adjuvant potential of natural polymers

RSC Advances ◽  
2014 ◽  
Vol 4 (27) ◽  
pp. 13817-13821 ◽  
Author(s):  
Akhilesh Kumar Shakya ◽  
Ashok Kumar ◽  
Kutty Selva Nandakumar
Keyword(s):  
Alginic Acid ◽  
Cross Linking ◽  
Natural Polymers ◽  
Chemical Cross Linking

Natural polymers like chitosan and alginic acid are extensively used in biomedicine for different applications.

scholarly journals Cross-Linking Strategies for Electrospun Gelatin Scaffolds

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2476 ◽  
Author(s):  
Chiara Emma Campiglio ◽  
Nicola Contessi Negrini ◽  
Silvia Farè ◽  
Lorenza Draghi
Keyword(s):  
Low Cost ◽  
Cross Linking ◽  
Fiber Morphology ◽  
Natural Polymers ◽  
Wide Availability ◽  
Fiber Scaffolds ◽  
Electrospun Gelatin ◽  
Physical And Chemical ◽  
Synthetic And Natural Polymers ◽  
Chemical Cross Linking

Electrospinning is an exceptional technology to fabricate sub-micrometric fiber scaffolds for regenerative medicine applications and to mimic the morphology and the chemistry of the natural extracellular matrix (ECM). Although most synthetic and natural polymers can be electrospun, gelatin frequently represents a material of choice due to the presence of cell-interactive motifs, its wide availability, low cost, easy processability, and biodegradability. However, cross-linking is required to stabilize the structure of the electrospun matrices and avoid gelatin dissolution at body temperature. Different physical and chemical cross-linking protocols have been described to improve electrospun gelatin stability and to preserve the morphological fibrous arrangement of the electrospun gelatin scaffolds. Here, we review the main current strategies. For each method, the cross-linking mechanism and its efficiency, the influence of electrospinning parameters, and the resulting fiber morphology are considered. The main drawbacks as well as the open challenges are also discussed.

scholarly journals FORMULATION AND EVALUATION OF RACECADOTRIL MUCOADHESIVE MICROSPHERES

2019 ◽  
pp. 55-61
Author(s):  
KANCHAN JAMKAR ◽  
SWATI MUTHA ◽  
SHARWAREE HARDIKAR ◽  
NIKHIL KUMBHAR
Keyword(s):  
Drug Release ◽  
Sustained Release ◽  
Xanthan Gum ◽  
Entrapment Efficiency ◽  
Cross Linking ◽  
Natural Polymers ◽  
In Vitro Drug Release ◽  
Mucoadhesive Microsphere ◽  
Chemical Cross Linking

Objective: To develop and evaluate the mucoadhesive microsphere using combinations of natural polymers chitosan and xanthan gum for sustained release. Methods: In the present work mucoadhesive microspheres were prepared by using natural polymers like chitosan and xanthan gum by using the emulsion chemical cross-linking method. Chemical cross-linking was done by using glutaraldehyde. The 22 factorial design was employed to show the effect of cross-linking agent and processing factor-like stirring and speed. Prepared microspheres were evaluated for their particle size, surface morphology, drug entrapment efficiency, in vitro drug release, swelling index, and mucoadhesive strength. Results: The size of microspheres of factorial batches were in the range of 26-46 µm. The swelling index was showed in the range of 1.51-1.66 percentage. The equation of multiple regression revealed that there was significant interaction among factors. The glutaraldehyde concentration had a positive effect on % entrapment efficiency, % cumulative drug release and % mucoadhesion. Stirring speed showed a negative impact on % entrapment efficiency, % cumulative drug release and % mucoadhesion. The interactive effect of glutaraldehyde concentration and the stirring speed was found to be positive for % entrapment efficiency and % cumulative drug release. In vitro drug release study of optimized formulation F2 show 96 % of drug release with 6 h indicating sustained release behavior with diffusion mechanism. The SEM image of the optimized batch was spherical with a porous surface. Conclusion: The results obtained in this research work indicated that a promising potential of chitosan and xanthan gum combination for the preparation of the mucoadhesive microsphere of Racecadotril.

Statistical Force-Field for Structural Modeling Using Chemical Cross-Linking/mass Spectrometry Distance Constraints

2018 ◽  
Author(s):  
Allan J. R. Ferrari ◽  
Fabio C. Gozzo ◽  
Leandro Martinez
Keyword(s):  
Mass Spectrometry ◽  
Amino Acid ◽  
Force Field ◽  
Protein Structures ◽  
Protein Structure Determination ◽  
Structural Modeling ◽  
Cross Linking ◽  
Amino Acid Residues ◽  
Distance Constraints ◽  
Chemical Cross Linking

<div><p>Chemical cross-linking/Mass Spectrometry (XLMS) is an experimental method to obtain distance constraints between amino acid residues, which can be applied to structural modeling of tertiary and quaternary biomolecular structures. These constraints provide, in principle, only upper limits to the distance between amino acid residues along the surface of the biomolecule. In practice, attempts to use of XLMS constraints for tertiary protein structure determination have not been widely successful. This indicates the need of specifically designed strategies for the representation of these constraints within modeling algorithms. Here, a force-field designed to represent XLMS-derived constraints is proposed. The potential energy functions are obtained by computing, in the database of known protein structures, the probability of satisfaction of a topological cross-linking distance as a function of the Euclidean distance between amino acid residues. The force-field can be easily incorporated into current modeling methods and software. In this work, the force-field was implemented within the Rosetta ab initio relax protocol. We show a significant improvement in the quality of the models obtained relative to current strategies for constraint representation. This force-field contributes to the long-desired goal of obtaining the tertiary structures of proteins using XLMS data. Force-field parameters and usage instructions are freely available at http://m3g.iqm.unicamp.br/topolink/xlff <br></p></div><p></p><p></p>

scholarly journals Structure of cyanobacterial phycobilisome core revealed by structural modeling and chemical cross-linking

2021 ◽  
Vol 7 (2) ◽  
pp. eaba5743
Author(s):  
Haijun Liu ◽  
Mengru M. Zhang ◽  
Daniel A. Weisz ◽  
Ming Cheng ◽  
Himadri B. Pakrasi ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Excitation Energy Transfer ◽  
Energy Coupling ◽  
Regulatory Elements ◽  
Photochemical Activity ◽  
Structural Basis ◽  
Bottom Surface ◽  
Cross Linking ◽  
Orange Carotenoid Protein ◽  
Chemical Cross Linking

In cyanobacteria and red algae, the structural basis dictating efficient excitation energy transfer from the phycobilisome (PBS) antenna complex to the reaction centers remains unclear. The PBS has several peripheral rods and a central core that binds to the thylakoid membrane, allowing energy coupling with photosystem II (PSII) and PSI. Here, we have combined chemical cross-linking mass spectrometry with homology modeling to propose a tricylindrical cyanobacterial PBS core structure. Our model reveals a side-view crossover configuration of the two basal cylinders, consolidating the essential roles of the anchoring domains composed of the ApcE PB loop and ApcD, which facilitate the energy transfer to PSII and PSI, respectively. The uneven bottom surface of the PBS core contrasts with the flat reducing side of PSII. The extra space between two basal cylinders and PSII provides increased accessibility for regulatory elements, e.g., orange carotenoid protein, which are required for modulating photochemical activity.

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