Food-Grade Microgels for Age-Related Macular Degeneration: Design, Fabrication, and Targeted Delivery

Age-related macular degeneration (AMD) is a leading cause of irreversible vision loss worldwide and is driven by complex pathophysiological processes, including oxidative stress, chronic inflammation, complement dysregulation, and vascular endothelial growth factor (VEGF)-mediated neovascularization. Nutritional interventions-particularly supplementation with carotenoids, omega-3 fatty acids, polyphenols, and essential micronutrients-have demonstrated clinical benefits in slowing disease progression, as evidenced by landmark trials such as AREDS and AREDS2. However, many AMD-relevant bioactives exhibit poor aqueous solubility, low chemical stability, and limited gastrointestinal bioavailability, which significantly constrain their therapeutic efficacy. Food-grade microgels have emerged as versatile colloidal delivery platforms capable of addressing these limitations through rational structural and physicochemical design. This review provides a systematic roadmap for developing food-grade microgels, organized into: (1) the molecular design of protein- and polysaccharide-based networks; (2) advanced fabrication strategies such as microfluidics and atomization; (3) spatiotemporal release programming within the gastrointestinal tract; and (4) multi-nutrient synergy for retinal protection. This approach highlights how controlled crosslinking, interfacial assembly, and tunable network architectures enhance nutrient stabilization. Particular emphasis is placed on spatiotemporal release programming within the gastrointestinal tract, including diffusion-limited gastric retention, pH- and bile-responsive swelling in the small intestine, and microbiota-triggered degradation in the colon. These mechanisms collectively enable region-specific release, improved micellar incorporation, enhanced systemic absorption, and more consistent retinal delivery. Furthermore, we discuss co-encapsulation strategies that accommodate both hydrophilic and lipophilic bioactives, thereby minimizing antagonistic interactions and enabling synergistic nutritional modulation of oxidative and inflammatory pathways implicated in AMD. A central novelty of this review is the integration of the gut-eye axis, framing microgel-based oral delivery as a systemic pathway to modulate retinal health via the intestinal environment. By bridging retinal disease biology with food colloid science, this review proposes food-grade microgels as a translational platform for next-generation nutraceutical interventions. The integration of programmable release behavior with clinically validated nutrient regimens offers a promising pathway toward more effective and mechanistically informed dietary management of AMD.