Selenized polysaccharides for antiviral applications: Backbone chemistry, multidimensional synergy, and structure-guided design.

Viral infections continue to drive interest in polysaccharide-based antiviral materials. Selenized polysaccharides combine the multivalent recognition capacity of carbohydrate backbones with selenium-related redox and immunomodulatory functions. However, current studies often conflate chemically selenized polysaccharides, biologically selenium-enriched polysaccharide fractions, and polysaccharide-stabilized selenium nanoparticles (PS-SeNPs), thereby compromising structural assignment and mechanistic interpretation. The novelty of this review is not simply to catalog reported activities, but to establish material boundaries for selenium-containing polysaccharide systems, define a minimum evidence chain for chemical identity, and propose a structure-guided design framework for antiviral applications. The required evidence includes parent-backbone characterization, selenium content and speciation, exclusion of free selenium and nanoselenium, valence-state analysis, conformational integrity, and structure-function controls. We analyze how backbone architecture, molecular weight, branching, selenium valence state, and modification site may determine antiviral potential through viral adsorption/entry blockade, redox regulation, innate immune activation, and selenoenzyme-related host protection. Structure-activity relationships (SARs) reveal bidirectional coupling between selenium and polysaccharide backbones. Direct antiviral evidence remains limited and heterogeneous, with many mechanisms still inferred from native polysaccharide or selenium biology. Future progress requires standardized controls, site-selective selenization, isotope tracing, in vivo fate analysis, pharmacokinetic and safety evaluation, and structure-guided design.