Table 1.

The preparation method of different hydrogels for encapsulation and delivery of nutraceuticals including phenolic bioactives, vitamins and probiotics, as well as their functions.

The nutraceuticals	Hydrogels	The preparation methods	Functions
Polyphenols (106)	egg white lysozyme hydrogels	The purified lysozyme monomers were lyophilized, which were further heated in pH 2 solution with protein concentration of 2 wt% in 90 °C oil bath for 8 hours under agitation, to fabricate the amyloid fibrils. Polyphenols were dissolved respectively in the 10 mMBis-Tris buffer (pH 6.8), The 2 wt% amyloid fibril solution (pH2) was blended with the polyphenol solution in equal volume for preparation hydrogels.	Hydrogels significantly promoted intestinal barrier function, suppressed the proinflammatory mRNA expression, and very significantly regulated gut microbial dysbiosis.
Green tea polyphenols (68)	novel polyelectrolyte complex hydrogels were developed by self-assembly of two kinds of polysaccharides including salecan and N,N,N-trimethyl chitosan	The salecan and TMC solutions were prepared, respectively. Salecan solution was added dropwise into TMC solution according to various volume ratios under sonication for 30min. Self-assembly precursor solution was thus formed and then poured into a circular glass mold at room temperature. The molds were then placed in a desiccator containing an appropriate amount of acetic acid solution and stayed for 2h until the solutions were transformed into PEC hydrogels.	The PEC hydrogels could play a good role of intestinal targeted nutrition transport.
Hydrophobic curcumin (109)	self-assembled acylated rapeseed protein isolate nanogels	A new biocompatible and self-assembled acylated rapeseed protein isolate(ARPI) based nanogels were fabricated by the chemcial acylation and heat-induced protein denaturation. Protein acylation reaction was performed on RPI with butanedioic anhydride.	Significantly increasing its anticancer activity against multiple cancer cell lines
Curcumin (110)	mixed hydrogels composed of whey protein aggregates (WPA)/k- carrageenan	Preparation of whey protein aggregates (WPA) by free radical cross-linking method. Curcumin dissolved in ethanol was mixed in a certain proportion with the prepared WPA solution for 8h at room temperature for prepare curcumin-loaded whey protein aggregates. Carrageenan prepared with polysaccharide hydrated overnight at 25°C was added to the WPA solution for preparation of polysaccharide/protein mixed gel pre-solutions.The gel pre-solutions were charged by 1.3% w/v GDL for formation GDL-induced gel.	Protecting curcumin within the upper gastrointestinal tract and deliver it to the colon.
Quercetin (111)	gelatin-chitosan hydrogels	Based on the changes in functional groups in the FTIR and DSC heatmaps, quercetin-loaded liposomes were embedded in a gelatin-chitosan hydrogel and ionic and covalent bonds between Na+ and mTGase reactions.	This lipid gel system can track multifunctional and effective molecules by changing their structural properties for controlled release in specific pH or enzyme induced burst environments.
Vitamin C (113)	salecan/chitosan PEC hydrogels	Chitosan was added to the salecan solution and mixed,and PEC hydrogels were formed upon exposure to acetic acid atmosphere for 3h.VC was loaded onto the PEC hydrogels using an equilibrium partitioning method.	Hydrogels showed excellent cytocompatibility and biodegradability.It can show a good nutrient delivery function in specific parts of the intestine.
Riboflavin (114)	whey microbeads	Microbeads was prepared by dissolving the denaturing whey protein solution by Gilson minipuls in CaCl2 for several hours.	Drying of the microbeads provided a significant decrease in riboflavin release rate in vitro compared to wet microbeads and also impeded microbead degradation.
Folic acid (115)	folic acid-copper alginate hydrogels	Folic acid hydrogels were prepared by mixing 1.3%(w/v) sodium alginate and 50%(w/w, wrt sodium alginate) folic acid for 20 minutes. The folic acid-sodium alginate solution and was added dropwise to the CuSO4 solution, and folic acid-copper alginate gels were formed in the process.	The copper alginate acted as gastro-resistant material and slow release of folic acid occurs.
Folic acid (116)	the compositions of biocomposite consisted of alginate and pectin	Alginate and pectin were mixed and dissolved in CaCl2 by a syringe pump to prepare into blank microglue, and folic acid was dispersed in this composite microcapsule.	Composite hydrogels provided the stronger protective effect and the sustained release behavior of folic acid was observed in simulated intestinal conditions.
Vitamin D3 (117)	the composite gel of whey protein isolate and lotus root amylopectin(WPI-LRA gels)	LRA and WPI solutions were prepared, mixed and heated through a water bath into the gels.Vitamin D3 were dissolved in ethanol,then was added to the WPI-LRA mixture,finally The above mixtures are heated,cooled and lyophilized.	This encapsulation could increase the storage stability of vitamin D3 and protect vitamin D3 from photochemical degradation. The in vitro experiment suggested that WPI-LRA composite gel could supply a protective barrier for vitamin D3 and prolong the residence time in intestine.
α-tocopherol (α-TOC) (118)	salt-induced proteingels based β-lactoglobulin or hen egg white protein	Salt-induced gelation technique was used for preparation of protein based-encapsulated α-TOC. Appropriate concentration of α-TOC was mixed with appropriate concentration of BLG solution and subsequently CaCl2, was added to induce aggregation of BLG. A method to prepare HEW-encapsulated α-TOC was similar to that of the BLG-encapsulated α-TOC except that ZnCl2 was added instead of CaCl2 to induce aggregation of BLG.	With the alginate coat, the release of α-TOC was retarded till intestinal stage and the encapsulation efficiencies of α-TOC by BLG and HEW were enhanced.
Lactobacillus plantarum ATCC:13643 (119)	pectin/starch hydrogels	Pectin/starch hydrogel were prepared by external gelation method at various pectin/starch ratios.Lactobacillus plantarum ATCC:13643 cells were encapsulated in pectin/starch hydrogel by extrusion method.	Incorporation of starch with pectin biopolymer provided significant protection for cells against the harsh conditions of simulated gastric tract.The pectin/starch hydrogel increased the tolerance of L. plantarum to strongly acidic media and bile solutions and enable probiotics to be delivered to the colon.
Probiotic Lactobacillus reuteri (128)	heteroprotein complex coacervation (type-A gelatin/sodium caseinate, GE/Cas)	The microcapsules were prepared using the method of coacervation or mixing, followed by spray drying.The control GE and Cas microcapsules were prepared at pH 6.0. The operation temperature for coacervation was kept at 40°C and the biopolymer solutions, sucrose and the probiotics were mixed.The mixture was finally adjusted with ph, ice bath and drying treatment.	Microencapsulation in GE/Cas improved the survival during dry storage,and the stability of the probiotic cells was improved.
Probiotics (130)	A novel NO-responsivepoly-γ-glutamic acid(γ-PGA) hydrogel microcapsule (NRPM)	Using a visible light poly-merization method to produced macroscopic NRPM hydrogels. The gelation mechanism was attributed to the formation of covalent C-C linkages between the C=C groups on the γ-PGA-GMA backbone and the terminal of	Owing to the cytoprotective effects of the NRPM, the decorated probiotics showed high viability in the simulatedgastric and intestinal fluid
		the APD.Meanwhile, it retained a benzotriazole group that acted as a targeted molecule capable of responding to NO. A transparent and homogeneous hydrogel formed within a controllable time from several seconds to several minutes.	environments. Microspheres can respond to nitric oxide(NO) stimuli and rapidly release probiotics to maintain the intestinal mechanical barrier and regulate the balance of intestinal flora. NRPM is a promising approach for improving the efficacy of orally administered probiotics in patients with colonic IBD.
Bacillus subtilis (BS) (135)	Self-coating with BS biofilms	Firstly, the biofilm-free BS was obtained, then the seed medium was suspended to obtain FCBS, and the cell pellets were collected and then suspended in PBS, the resulted solution was spread on solid MSgg plates. Robust BS biofilms were produced after 2 days of culture at 30°C. Individually coated bacteria BCBS were prepared by homogenizing the films with PBS.	Self-coating with biofilms that endows the transplanted gut microbiota with superior resistance and adhesion capacity.Coated probiotics exhibit a higher oral bioavailability,intestinal colonization and notable ability to survive and reside in the GI tract.