Effect Of Molecular Weight On The Properties Of Quercetin-Loaded Chitosan Nanoparticles And Films

Petroleum-based plastic materials are over-consumed and are difficult to degrade,causing serious environmental pollution and even threatening human health.Therefore,environmentally friendly bio-based materials that can replace plastics,such as lipids,proteins and polysaccharides,are becoming increasingly popular.These bio-based materials are non-toxic,biodegradable,biocompatible and have been developed into edible films with a wide range of promising applications in the food industry.Chitosan(CS)has been widely used in food packaging because of its good film-forming properties,biodegradability and non-toxicity.However,its restricted antioxidant and antimicrobial activities have limited its application to some extent.In this study,film with antioxidant activity based on satisfying physical and mechanical properties was prepared by adding quercetin-loaded chitosan nanoparticles(QCNP)and using CS as film-forming matrix,and the influence of chitosan molecular weight to the film characteristics was also evaluated.There were main conclusions as follows:Firstly,chitosan nanoparticles(CNP-10、CNP-20、CNP-50、CNP-100)using four chitosan molecular weights(Mw: 100 k Da,200 k Da,500 k Da,1000 k Da)were prepared by ionic cross-linking method.When the CS concentration was 0.8 mg/m L,CS/TPP was 4:1 and the solution p H was 5,the particle size of CNP-10、CNP-20、CNP-50 and CNP-100 were 178.3,185.3,167.1 and 171.3 nm,respectively,the PDI was less than 0.3 and the potential was greater than +30 m V,which indicated that the nanoparticles prepared under these conditions were uniformly distributed and highly stable.Among them,QCNP-50 had the smallest particle size,the highest potential and the clearest solution.FTIR analysis showed that the phosphate group in TPP was bound to the amino group in CS by electrostatic interaction.Furthermore,four chitosan nanoparticles were prepared into films(CNP-10 film、CNP-20 film、CNP-50 film and CNP-100 film)by using the tape casting method.Their physical and mechanical properties were investigated.Compared with the CS film,the addition of chitosan nanoparticles reduced the tensile strength of the films,but enhanced the water vapor barrier properties of the films and improved the elongation at break.Among them,CNP-50 film had the highest tensile strength,elongation at break relative to other chitosan nanocomposite films.Quercetin-loaded chitosan nanoparticles(QCNP-10 、 QCNP-20 、 QCNP-50 、QCNP-100)using four chitosan molecular weights(Mw: 100 k Da,200 k Da,500 k Da,1000 k Da)were prepared under the conditions of the CS concentration was 0.8 mg/m L,CS/TPP was 4:1 and the solution p H was 5.And the effect of chitosan molecular weight on the performance of nanoparticles was investigated.The results showed that the particle size of QCNP decreased with the increase of molecular weight to 394.8,360.7,330.4 and 327.9 nm,respectively,and the PDI of QCNP increased with the increase of molecular weight to 0.265,0.294,0.331 and 0.366,respectively.DLS,FTIR and UV-vis demonstrated the successful embedding of nanoparticles.With the increase of molecular weight,the antioxidant activity of QCNP increased gradually,which may be related to its smaller particle size.In vitro release experiments demonstrated that chitosan nanoparticles slowed down the release rate of quercetin and increased its release cycle.The release rate decreased in the following order QCNP-20 > QCNP-10 > QCNP-50 >QCNP-100.Among them,QCNP-100 had the minimum particle size,the highest antioxidant activity and the lowest release rate.Finally,the above synthesized QCNP-10,QCNP-20,QCNP-50,and QCNP-100 were mixed with chitosan,gelatin and other materials respectively,and films(QCNP-10,QCNP-20,QCNP-50,and QCNP-100 films)were prepared by using the tape casting method.Their physical,mechanical and biological properties were further investigated.Compared with the CS film,the water vapor barrier property and tensile strength of the QCNP films decreased,the water solubility decreased,the contact angle decreased,the UV barrier property was enhanced,and the antioxidant activity was greatly increased.It was worth mentioning that the addition of QCNP greatly enhanced the antioxidant activity of CS film.With the increase of molecular weight,the DPPH radical scavenging rate of QCNP films increased to be 35.35%,42.88%,44.70% and 50.08%respectively,and the ABTS radical scavenging rate of QCNP films increased to be72.31%,75.13%,85.51% and 88.05% respectively.Among QCNP films,QCNP-10 film had the highest tensile strength and the lowest water solubility,and QCNP-100 film had the highest UV light barrier performance and antioxidant activity.In conclusion,the difference in molecular weight makes a significant effect on the nanoparticles,and the addition of nanoparticles can further affect the properties of the films.The quercetin-loaded chitosan nanoparticles film is a promising material for food active packaging,and the present experimental study provides some reference for its commercial production.