The International Scientific Association for Probiotics and Prebiotics (ISAPP) defines a prebiotic as “a substrate that is selectively utilized by host microorganisms conferring a health benefit”^[14]. This functional definition is more stringent than the broader concepts of dietary fiber or fermentable polysaccharides: microbial degradability alone is insufficient, and a material should be considered a prebiotic only when selective utilization is linked to a measurable host benefit.

Prebiotics with comparatively strong evidence include inulin-type fructans and fructo-oligosaccharides (FOS), galacto-oligosaccharides (GOS), selected resistant starches, β-glucans, xylo-oligosaccharides (XOS), and other structurally defined oligosaccharides; pectin and pectic oligosaccharides have increasingly substantial but structure-dependent evidence^[11,15]. Chitosan, alginate, and hyaluronic acid should not automatically be labeled prebiotics; without evidence of selective utilization and host benefit, they are better described as bioactive polysaccharides or delivery materials. Here, “prebiotic-integrated” refers to nanosystems that incorporate a carbohydrate with established or proposed prebiotic activity in its native form. Whether that activity survives nanoengineering is evaluated separately rather than assumed from the material composition.

Representative prebiotics differ markedly in fermentation region, dominant utilizers, and fermentation kinetics. Inulin-type fructans are generally fermented relatively rapidly and tend to support bifidobacteria-associated niches in the proximal-to-mid colon; pectin fermentation is more strongly influenced by molecular weight, branching, and degree of esterification and may extend across multiple colonic regions; resistant starch is degraded more slowly and may sustain saccharolytic substrate availability further into the distal colon^[16-20]. Beyond these three classes, GOS, XOS, and selected structurally defined β-glucans also show substantial evidence of selective microbial utilization, although responder taxa and fermentation outputs remain dependent on degree of polymerization, branching, and the baseline host microbiome. Representative microbial taxa involved in fermentation, major fermentation products, and fermentation profiles of selected prebiotics are summarized in Table 1.

Prebiotic action in IBD is best viewed as a sequence rather than as several independent effects. Microbial use of the substrate first changes community interactions; the resulting shifts in fermentation and metabolic output then influence the epithelial barrier and mucosal immune system.

The same substrate can produce different microbial and metabolic responses because patients differ in relevant transporters, glycosidases, primary degraders, and cross-feeding partners^[11,25]. Nanoengineering can alter where and when a substrate is delivered, but it cannot replace microbial functions that are absent. Patient or microbiome stratification therefore remains important.

Free prebiotics are often administered at gram-scale doses, yet dissolved substrates disperse through the intestinal lumen rather than accumulating at ulcerated sites. They are also difficult to co-localize with epithelial or immune-cell targets. Nanoscale carriers may reduce this spatial mismatch by concentrating the prebiotic-derived structure and its co-therapeutic cargo in selected gastrointestinal regions or inflamed tissue, provided that the formulated carbohydrate remains biologically accessible.

Rapid exposure to soluble fermentable substrates can increase gas production and contribute to bloating, abdominal pain, or altered bowel habits. In active Crohn’s disease, 15 g/day FOS did not improve clinical response and was associated with a higher withdrawal rate^[34]. Engineered systems could, in principle, stage substrate exposure through controlled dissolution, enzyme-responsive disassembly, or changes in accessible surface area, but clinical evidence that nanostructuring reduces fermentation-related intolerance is not yet available.

Microbiota-dependent effects may also be too slow for active disease with a high inflammatory or oxidative burden. Co-delivery with faster anti-inflammatory, antioxidant, biological, metabolic, or gas-releasing modules is therefore intended to bridge this kinetic gap rather than to replace the prebiotic component.

Prebiotic polymers can form nanoparticles without permanent hydrophobic grafts through intrinsic aggregation or non-covalent complexation. Enzymatically synthesized high-molecular-weight inulin, for example, formed stable spherical particles with an average diameter of about 112 nm above a critical aggregation concentration^[36]. In a more recent formulation, calcium chloride was used for ionotropic gelation and natural honey for stabilization of inulin nanoparticles intended for colon-targeted delivery^[37]. The earlier high-molecular-weight inulin particles showed no significant prebiotic activity in the probiotic strains tested, illustrating that nanoscale assembly and prebiotic function do not necessarily track together.

Pectin provides a complementary route because its charge enables ionic gelation and polyelectrolyte complexation with cationic polymers. Colon-directed systems have been prepared with trimethyl chitosan or chitosan/tripolyphosphate, with polymer ratio, charge density, pH, ionic strength, and crosslinker concentration controlling particle size and stability^[38,39]. These studies establish pectin as a useful construction and colon-delivery material, but they do not by themselves show that the engineered pectin retains selective prebiotic activity in IBD.

Covalent modification is useful when a hydrophilic prebiotic must be converted into an amphiphilic carrier. Inulin contains abundant hydroxyl groups that can be grafted with hydrophobic segments, producing structures that self-assemble into micelles or core-shell nanoparticles. Reported examples include succinyl-ceramide/polyethylene glycol (PEG) graft copolymers^[40], inulin-poly (D, L-lactide) (INU-PLA) nanoparticles with an inulin-rich corona whose organization depends on surface density^[41], vitamin E-modified pH-sensitive nanomicelles^[42], and propionylated or propyl inulin nanoparticles^[43]. The same principle has been applied to pectin: pectin-doxorubicin conjugates containing acid-sensitive hydrazone linkages can co-self-assemble with hydrophobic drugs into pH-responsive nanoparticles^[44].

Chemical modification offers structural control but can also mask glycosidic motifs or reduce enzyme accessibility. Degree and position of substitution should therefore be considered in relation to microbial utilization, not only particle formation.

A prebiotic does not need to form the entire particle to contribute to a nanoscale platform. It can instead serve as a co-assembling component or surface layer, leaving the core to provide drug loading or structural stability while the carbohydrate interface contributes gastrointestinal protection and, potentially, microbial accessibility. Pectin has been incorporated into whey-protein-isolate/zein nanoparticles^[45] and deposited onto preformed liposomes to improve stability during simulated digestion^[46]. In a multicomponent IBD system, inulin, trans-ferulic acid, and silk sericin were assembled into nanoparticles before being immobilized on coated Bifidobacterium longum^[47]. Only the nanoparticle component is considered here because the subsequent whole-cell construct lies outside the nanoscale scope of this review.

Scope also depends on where the carbohydrate sits in the formulation. The scope includes systems in which the prebiotic forms part of the nanoparticle core, shell, or nanoscale interface, but excludes nanoparticles that are simply embedded in a bulk prebiotic hydrogel or another macroscopic matrix. The latter are better considered hydrogel-based delivery systems rather than nanoscale prebiotic platforms.

Physical processing offers a route to nanoscale organization without extensive covalent derivatization. Resistant-starch nanoparticles have been produced by pullulanase-mediated debranching followed by nanoprecipitation^[48] and by ultrasound-assisted enzymatic restructuring^[49]. Pectin nanoparticles have also been prepared from nanoemulsion templates generated by high-pressure homogenization^[50]. These methods may preserve more of the native chemistry than extensive grafting, but they can still change molecular weight, branching, crystallinity, surface accessibility, and fermentation behavior. Those changes are relevant to microbial utilization as well as to particle properties.

Most reports in this area still emphasize particle formation and delivery performance. Direct comparisons of native and engineered carbohydrates with respect to microbial degradation, fermentation, and metabolic output remain uncommon and should complement routine physicochemical characterization.

Successful incorporation of a prebiotic carbohydrate into a nanoscale formulation does not by itself demonstrate retention of prebiotic function. Evidence can be considered at three levels. Direct evidence includes demonstrated microbial utilization or degradation of the engineered carbohydrate together with fermentation or metabolite production. Intermediate evidence includes microbiota and metabolite changes that are associated with the engineered carbohydrate but are not experimentally separated from other formulation components. Indirect evidence is limited to changes in microbiota composition or disease phenotype without direct demonstration of carbohydrate utilization. This distinction is particularly important for chemically modified, densely crosslinked, or surface-confined carbohydrates, whose accessibility to microbial enzymes may differ substantially from that of the native substrate.

Accordingly, future studies should compare native and engineered forms using microbial degradation assays, fermentation kinetics, SCFA or other metabolite measurements, and appropriate carrier-only controls. Microbiota-associated changes alone are therefore not considered sufficient to establish retained prebiotic activity.

Selected ionic, amphiphilic, composite, and multilayer architectures are shown in Figure 2. Several examples were developed outside IBD and are included only to illustrate construction or oral-delivery principles that can be transferred to prebiotic nanomedicine.

A straightforward combination strategy pairs a prebiotic nanocomponent with an established anti-inflammatory drug. The carbohydrate can contribute gastrointestinal protection, colon-responsive disassembly, or local retention, while the drug directly suppresses inflammatory signaling. If the engineered carbohydrate remains available to the microbiota, the same formulation may also address ecological functions that conventional drugs do not directly restore.

Bud@MSN-IN illustrates this division of labor: budesonide-loaded mesoporous silica nanoparticles were coated with inulin^[54]. The coating improved upper-gastrointestinal stability and enabled inulinase-responsive release in the colon, while budesonide supplied the rapid anti-inflammatory effect. Treatment was also associated with improvements in oxidative-stress and microbiota-related indices, and unloaded inulin-coated particles showed measurable biological activity. These findings are consistent with a contribution from the inulin layer, although selective microbial utilization of the engineered coating was not directly traced.

A key experimental issue is therefore not only whether the combined formulation is effective, but also whether the drug, carrier, and prebiotic make distinguishable contributions. Appropriate controls are needed to distinguish pharmacological activity from carrier effects and microbiota-dependent effects.

Beyond conventional drugs, nanoscale prebiotic systems can improve the oral delivery of bioactive agents that are poorly soluble, unstable, rapidly metabolized, or poorly retained in inflamed intestinal tissue. The carbohydrate usually contributes assembly and gastrointestinal handling, while the cargo supplies a more direct pharmacological or regenerative effect.

TPP-IN-LA/CBD used chemically modified inulin to formulate mitochondria-targeted, glutathione-responsive cannabidiol nanoparticles^[55]. Importantly, this study evaluated the platform in a preventive colitis setting rather than as treatment of established disease. Under this regimen, the formulation reduced Toll-like receptor 4 (TLR4)/nuclear factor kappa B (NF-κB)-associated inflammatory responses, improved epithelial-barrier markers, and was accompanied by changes in microbial composition and SCFA levels. However, microbial utilization of the modified inulin was not isolated from the overall formulation effect. Hesperetin-zinc and epigallocatechin gallate-manganese (EGCG-Mn) systems^[56,57] also use prebiotic carriers; because redox regulation is their main added function, they are considered in Section Combination with antioxidant therapeutics.

Microbial metabolites can also be incorporated directly. The inulin-butyrate nanogel combines a fermentable carbohydrate with butyrate replacement in the same nanoscale structure^[58]. It accumulated preferentially in inflamed colonic tissue and underwent inulinase- and esterase-responsive degradation. Microbiota remodeling, barrier recovery, and regulatory T-cell responses accompanied treatment, allowing the supplied butyrate to act early while inulin remained available for slower microbiota-dependent effects.

Biological cargos extend this concept beyond small molecules. Engineered extracellular vesicles and bacterial outer membrane vesicles can carry activities that are difficult to reproduce with conventional drugs^[59]. The inflamed-colon-targeted hybrid nanotherapeutic (ICHN) combined inulin with mitochondria-targeted cerium-based nanocomponents and mesenchymal stromal cell-derived extracellular vesicles (MSC-EVs)^[60], with concurrent effects reported on mitochondrial oxidative injury, macrophage polarization, epithelial repair, and dysbiosis. Because several active modules were present, the microbiota response cannot be assigned specifically to inulin.

Oxidative injury provides a mechanistic rationale for adding a fast-acting module to a prebiotic platform. Redox-active agents can lower RONS before microbiota-mediated metabolic recovery is established; reported systems range from small-molecule or coordination complexes to catalytic nanozymes^[61-64].

Hes-Zn@IN and BG@EGCG-Mn represent the small-molecule/coordination end of this spectrum^[56,57]. Hes-Zn@IN couples a hesperetin-zinc core with an inulin-containing shell that supports pH-dependent delivery and accumulation in inflamed colon tissue. BG@EGCG-Mn uses oat β-glucan nanoparticles to carry an EGCG-Mn complex. Both systems were associated with improvements in barrier and microbiota-related outcomes, although fermentation of the engineered carbohydrate was not traced directly.

Catalytic systems pursue the same goal through enzyme-mimetic RONS removal. CeO₂@IN places an inulin coating around cerium oxide nanoparticles^[62]; the ceria core exhibited superoxide-dismutase- and catalase-like activity and was reported to preserve epithelial integrity, while the coating supported oral delivery. PSGI refers to a nanosystem comprising sulfasalazine-loaded hollow mesoporous Prussian blue nanoparticles encapsulated in a glutamine-modified inulin nanogel^[63]. Here, catalytic antioxidant activity and drug therapy are paired with upper-gastrointestinal protection and enzyme-responsive colonic release. In both systems, the delivery role of inulin is clear, but post-engineering microbial utilization was not separated from the overall treatment effect.

Resistant starch has also been incorporated into cerium-sulfasalazine infinite coordination polymers (Ce-SASP-RS ICPs)^[64]. The system showed multienzyme-like redox activity and microbiota-associated changes; however, gastric instability necessitated intraperitoneal administration. Because this route bypasses luminal gastrointestinal exposure, direct intestinal microbial utilization of the resistant-starch component cannot be assumed. This system is therefore better regarded as a proof-of-concept for resistant-starch-containing multimodal nanotherapy rather than direct evidence for oral prebiotic-integrated nanomedicine.

Gasotransmitters extend the same fast/slow design logic. At low local concentrations they can rapidly influence redox-sensitive and immune-regulatory pathways^[65], but gastrointestinal delivery is complicated by instability, uncontrolled release, and short local exposure. A prebiotic-derived carrier may help localize the gas donor while retaining a substrate for later microbial and metabolic effects.

DATS-loaded inulin-PCL nanomicelle (DIP) is an oral inulin-grafted polycaprolactone nanomicelle carrying diallyl trisulfide as a hydrogen sulfide (H₂S) donor^[66]. Intracellular glutathione promoted H₂S generation, activating heme oxygenase-1 (HO-1)-associated antioxidant responses and suppressing the phosphorylated signal transducer and activator of transcription 3 (p-STAT3)/Th17/interleukin-17 (IL-17) axis. Treatment also increased Lactobacillaceae and Muribaculaceae and raised acetate and butyrate levels; multi-omics analyses linked these changes with immune regulation, epithelial repair, and barrier recovery. Unlike systems in which the carbohydrate primarily serves as a coating, DIP was designed to couple microbiota-associated changes with gas-mediated activity within the same formulation. It therefore illustrates a strategy in which a prebiotic-derived nanocarrier is integrated with local gasotransmitter generation. Nevertheless, direct demonstration of microbial utilization of the engineered inulin component remains important for distinguishing retained prebiotic activity from broader treatment-associated microbiota changes.

Mechanistically interpretable combination designs assign distinct functions to the prebiotic and the co-therapy. The added module should address a defined deficit - rapid control of inflammation, oxidative injury, or metabolite shortage - while the carbohydrate retains a measurable delivery or microbiota-related function. This also dictates the control groups: multicomponent systems should be compared with simpler formulations so that the contribution of each module can be resolved. Figure 3 broadens this comparison with pectin-based systems carrying sulfasalazine, azathioprine, or celastrol^[67-69], whereas Figure 4 contrasts a β-glucan/polydopamine antioxidant platform with the DIP H₂S system^[61,66]. Representative platforms are summarized in Table 2.

Clinical evidence for prebiotics in IBD comes mainly from free dietary substrates rather than nanoengineered formulations. Inulin-type fructans and 1-kestose have shown potential benefits in selected UC populations, including changes in clinical activity, fecal calprotectin, microbiota composition, or SCFA production^[24,70,71]. The results are not uniform: FOS failed to improve active Crohn’s disease in a randomized trial^[34], and recent meta-analyses report heterogeneous efficacy with generally limited certainty^[31,32].

These findings justify continued interest in microbiota-directed therapy, but they cannot be extrapolated directly to prebiotic nanomedicine. Most nanoformulations have been tested in chemically induced colitis, which is useful for early efficacy studies but does not capture the chronic, relapsing, and heterogeneous course of human IBD. More informative validation would include chronic or recurrent models, comparison with established treatments, and sustained remission rather than only short-term endpoints^[12,13].

A recurring uncertainty is whether the carbohydrate still behaves as a prebiotic after it has been engineered. Nanostructuring can change molecular weight, branching, degree of substitution, glycosidic accessibility, and degradation kinetics, all of which may alter fermentation. The point is illustrated by self-assembled high-molecular-weight inulin nanoparticles: particle formation was successful, but prebiotic activity was not detectable in the tested probiotic strains^[36].

For this reason, a shift in microbiota composition should not be treated as sufficient evidence of retained prebiotic function. Native and engineered forms should be compared directly for microbial degradation, fermentation behavior, and relevant metabolic outputs. Substitution degree, crosslink density, and surface accessibility should also be related to microbial utilization rather than reported only as physicochemical variables^[11,12].

Patient-to-patient variability adds a second layer of uncertainty. Relevant degraders, carbohydrate-active enzymes, and cross-feeding networks differ with diet, medication exposure, disease location, and inflammatory activity^[1,11,15]. Functional microbial features may therefore be more useful for patient stratification than taxonomic composition alone.

Systemic pharmacokinetics alone are a poor description of exposure for an oral, colon-directed prebiotic nanomedicine. More relevant measurements include upper-gastrointestinal stability, regional disassembly, mucus interaction, retention in inflamed tissue, microbial degradation, local generation of metabolites or therapeutic agents, and elimination^[12,13]. These measurements are especially important for enzyme-responsive and gas-releasing systems, whose activity depends on sequential events at specific intestinal sites.

Dose also needs to be interpreted differently from free prebiotic supplementation. Dietary interventions commonly use gram-scale amounts, whereas a nanoformulation may contain only milligrams or micrograms of carbohydrate and may alter where that carbohydrate becomes accessible. Dose-ranging studies should therefore pair conventional pharmacokinetic or efficacy measurements with gastrointestinal tolerability and fermentation readouts.

Safety assessment should address both the carrier and the engineered carbohydrate. Chemical modification can introduce residual reagents or new degradation products, while inorganic nanozymes and other persistent materials raise questions about long-term retention and repeated dosing. Fermentation-related gastrointestinal effects and unintended release of highly active cargos also need to be characterized. Because IBD treatment is often prolonged or recurrent, repeated-dose local and systemic safety is more informative than short-term tolerability alone.

Manufacturing reproducibility is particularly challenging when natural polysaccharides are used as functional components. Biological source, extraction, molecular-weight distribution, branching, and degree of esterification can vary between batches, and chemical modification adds further variability in substitution and residual reactants. Particle size distribution, surface composition, loading, stability, and release behavior also require consistent control^[12,13].

Quality control should therefore include biological attributes when efficacy depends on preserved prebiotic function. Microbial degradability and fermentation behavior may be as important as conventional physicochemical specifications. Complexity also matters: formulations that combine drugs, nanozymes, extracellular vesicles, or gas donors are more difficult to scale, sterilize, store, and characterize. Additional components should be retained only when they provide a distinct, experimentally supported function.

A clinically credible prebiotic nanomedicine will ultimately need reproducible manufacturing, documented prebiotic activity, predictable gastrointestinal behavior, acceptable long-term safety, and a patient-selection strategy compatible with microbiome variability. Accordingly, translational success will require simultaneous control of material quality, gastrointestinal behavior, microbiological function, and patient-dependent biological variability rather than optimization of nanoparticle properties alone. These requirements are likely to be more decisive for translation than efficacy in a short-term colitis model alone.