Fabrication Of Biocompatible Cassava Starch Based Nanoparticles And Their Potential Stabilization For Pickering Interfacial

Different from traditional emulsions,Pickering emulsion is a novel emulsion stabilized by interfacially-adsorbed solid particles,that exhibits an effective resistance on coalescence and Ostwald ripening,and harmful effects linked to traditional emulsifiers.It has gained increasingly considerations to be applied in food,pharmacy,daily chemicals,crude oil recovery,emulsion polymerization and other fields.The suitable solid particles should be small particle size,low surface charge and bidirectional wettability,which allow them to firmly accumulate at the oil-water interface to form a stable physical barrier.Some inorganic and synthetic polymer particles have showed some feasibility to stabilize Pickering emulsions.Recently,to meet the consumers strong demands trend about formulated products on theoretical edible,natural,green and clean label,biomass resources are encouraged to be developed as solid particle Pickering stabilizer.In this dissertation,several nanoparticle stabilizers were fabricated with cassava starch,using efficient precipitation,surface modification and lipid complexation.Their physicochemical properties,emulsification stability,functional delivery ability and other performances were characterized to evaluate their potential feasibility in emulsification application.It was expected to provide theoretical guidance and technical support for formulating starch-based emulsifier and functional delivery systems.The main contents are addressed as following:1.Ultrasonic-assisted technique and alcohol nanoprecipitation were used to improve the efficiency of starch nanosizing,where the concentration starch solution was raised to 5-10 w/v%.The particle size was successfully controlled to smaller than 1000 nm.Subsequently,a hot-alcohol treatment was applied to crystallize the starch nanoparticles(StNPs)obtained from nanoprecipitation.After a 120 min hot alcohol treatment at 130°C,StNPs were transformed into V-type crystal starch nanoparticles(C-StNPs)with a crystallinity of 9.71%,suggesting that hot alcohol crystallization was potential to the crystal ion of StNPs.StNPs and C-StNPs can successfully form Pickering emulsion with a relatively stability,when the particle adding amount was higher to help improving the droplets surface coverage rate and reduce the droplets size.Addition of 4 w/v%StNPs or C-StNPs was observed to stabilize form Pickering emulsions(30 v/v%oil)within a 5-d storge,showing a short-term stabilization.Moreover,the stabilization effect between StNPs and C-StNPs was not significantly different.2.StNPs were in-situ surface acetylated under a mild condition(50-75°C)to obtain starch nanoparticles acetate(StNPAc)with DS range from 0.007 to 0.53.The particles morphology was changed insignificantly after modification.The surface hydrophobicity was relatively improved,because contact angle of the particles increased from 24.93°±0.74°(StNPs)to 89.56°±0.56°(StNPAc,DS0.53).And an approximately 25%digestibility rate in the 120 min simulated in vitro digestion was decreased comparing to StNPs,showing a higher enzymolysis resistance.StNPAc with different DS can form Pickering emulsion,but the stability of emulsion increased with DS of particles.StNPAc was adsorbed at the oil-water interface of droplets by CLSM,which was an important characteristic of the most Pickering emulsions.It suggested that the stabilization of droplets and emulsions was attribute to tight physical barrier constructed by the interfacially adsorbed StNPAc.Addition of 1.2 wt.%StNPAc with different DS can form Pickering emulsion,but the stability of emulsion increased with DS of particles.1.5 wt.%StNPAc(DS 0.53)exhibited a better emulsifying stability than StNPs in the oil-water ratio of 3:7(v/v)emulsion system,which were stable over 35 d.The droplet size was a quasilinear function as the adding amount of StNPAc.Large addition and small droplets size were conducive to produce a higher emulsifying stability.StNPAc based emulsion provided curcumin with a rate beyond 70%in encapsulation rate,storge retention rate(65 d)and ultraviolet radiation retention rate(24 h).It showed that StNPAc obtained by surface acetylation had potential to stabilize food Pickering emulsion without surfactant-free.or more3.Cassava starch nanoparticles etherified by n-butyl glycidyl(StNP-BGE)were prepared by directly surface etherification on StNPs particles under mild alkaline conditions.DS of several StNP-BGE particles after etherification was approximately 0.179,0.048,0.013 by ~1H-NMR analysis.DLS analysis showed that the particle size of StNP-BGE particles increased with the increase of ambient temperature.The transmittance test using visible light showed that the transmittance of the StNP-BGE aqueous suspension decreased with the increase of ambient temperature.It indicated that StNP-BGE had synchronous response characteristics to changing ambient temperature,and it was a kind of temperature-sensitive starch nanoparticles with LCST at approximately 30°C.StNP-BGE particles were used to prepare Pickering emulsion.The adding amount of StNP-BGE had influence on the formation and stability of emulsions.The emulsions were hardly formed with only 0.01-0.1wt.%particles.1.0 wt.%StNP-BGE stabilized the emulsions(1:9,v_O/v_W)for more than 40 d,while the addition of 1.5w/v%stabilized the emulsions for at least 60 d.When the oil phase contained VE by 30 mg/m L,StNP-BGE emulsions were used to encapsulate vitamin E(VE),with an encapsulating rate of VE at 84.94%.After a 29-d storage,the retention rate of VE in the emulsions was still 81.25%,which was 2.57 times to the residual VE in the VE-Sb O oil phase.Exposed to ultraviolet radiation for 24 h,the VE retention rate was also 74.14%,which was 3.85 times of that in VE-Sb O oil phase with a same radiation experience.The 120 min cumulative release ratio of VE in the emulsions were 69.84%(27.5°C)and 60.86%(30°C),while it was all below35%at 32.5°C,37.5°C and 35°C.These results confirmed that the ambient temperature had a significant effect on the release of VE in StNP-BGE emulsion,which was related to the temperature sensitivity of StNP-BGE particles.The fitting of various mathematical models showed that the VE release kinetics was related to the coexistence of Fickian diffusion and dissolution mechanisms in spherical matrix.In short,StNP-BGE had the potential to protect VE and control its release through interface adjustment.4.Cassava starch stearic acid complex nanoparticles(CSSNs)were prepared by combining amylopectin-rich cassava starch solution with stearic acid.The structure and properties of the particles were analyzed by iodine colorimetry,XRD and FTIR.The microscopic morphology of the CSSNs particles were irregular spherical shape by SEM,and particle size of CSSNs was mainly distributed around 50-800 nm by DLS.The complexing index of CSSNs was 3-27%,and showed a V-type characteristics crystalline structure and an infrared short-range ordering as other starch lipid complex.The contact angle of CSSNs(CPI 27.66%)was approximately 60.30°.The addition of 7 w/v%CSSNs-27could stabilize Pickering emulsion for more than 60 d.The prepared emulsions stabilized at p H 5.6-9.0,and exhibited a good resistance on the influence of 0.01-0.1 mol/L ionic strength(Na Cl)and the heating below 80℃.This study showed that CSSNs particles derived from high amylopectin cassava starch was also a potential edible Pickering stabilizer.5.To study the influence of amylose on the emulsifying capacity of complex nanoparticles,enzymatic debranching was used to increase the amylose content of cassava starch.The obtained parameters for enzymatic hydrolysis included 5.0w/v%cassava starch,50 U/g pullulanase,p H 4.8 of starch solution,60°C of temperature and 120 min of time,that possibly produced more debranched starch.The rational complexations with stearic acid for 120 min provided debranched cassava starch stearic acid complex nanoparticles(D-SSCNPs)with a higher CPI about 32.84%.Diffraction peak appeared 13°and 21°by XRD,indicating that D-SSCNPs performed a V-type crystalline characteristics.The average particle size,crystallinity and short-range order of D-SSCNPs were larger than that of D-StNPs.The contact angles of D-SSCNPs were found increasing with the increase of CPI.The storage test showed that D-SSCNPs had a better stabilization than D-StNPs.An addition of 4 w/v%D-SSCNPs stabilize the emulsion over a month.The above results showed that,when comparing to CSSNs and D-StNPs,D-SSCNPs were more effective to stabilize emulsion.D-SSCNPs is another novel potential theoretically edible Pickering stabilizer produced from another non-chemical biocompatible fabrication technique.In conclusion,cassava starch-based nanoparticles have been successfully fabricated to form Pickering emulsions,using an efficient ultrasonic-assisted alcohol nanoprecipitation,hot-alcohol crystallization,surface modification on nanoparticles,biological debranching and simple lipid complexing process.The resulting formulations revealed that,the obtained starch-based nanoparticles derived from biomass were theoretically edible and biocompatible;performed some classical Pickering interface behavior and emulsifying stability;exhibited lipophilic encapsulation and release-controlling properties.Ultimately,the obtained starch-based nanoparticles have practical potential for industrial purposes,including food,cosmetics and pharmaceutical industries.