Cyclodextrin Complexation in Pharmaceutical Systems

Cyclodextrins are cyclic oligosaccharides characterised by a truncated-cone shape with a hydrophobic central cavity and hydrophilic outer surface. These macrocycles form non-covalent inclusion complexes with a wide range of pharmaceutical agents, enhancing aqueous solubility, chemical stability and bioavailability without covalent modification of the drug. Natural cyclodextrins (α, β and γ) differ in cavity size, whereas chemically modified derivatives (for example hydroxypropyl- or methyl-substituted forms) offer tailored solubility and loading capacity. Inclusion complexation is governed by stoichiometry, association constant and the physicochemical properties of both guest and host. In formulation, cyclodextrins may interact with excipients—polymers, surfactants or preservatives—to modulate complexation efficiency and release kinetics. Beyond simple solubilisation, advanced systems exploit host–guest self-assembly to build stimuli-responsive carriers such as polyrotaxanes, nanosponges and supramolecular polymers, enabling targeted or sustained release, imaging and diagnostic applications. Safety and biodegradability profiles are well established, supporting both oral and parenteral routes. Challenges remain in scaling production of high-purity derivatives and in optimising dosage forms to balance cyclodextrin quantity with therapeutic dose. Globally, cyclodextrin complexation underpins numerous marketed products, from improved oral formulations to injectable vehicles, and continues to drive innovation in nanomedicine and functional drug delivery platforms.

Research from Nature Portfolio

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Research from all publishers

Recent work has refined the understanding of cyclodextrin–drug interactions to optimise solubilisation and permeation. A comprehensive review of natural and modified cyclodextrins detailed the influence of substitution type and degree on aqueous solubility and aggregate formation, emphasising the need to balance complex stability with free-drug release. This analysis also highlighted how competitive binding with polymers and surfactants can be leveraged to fine-tune formulation behaviour and membrane transport in vitro and in vivo. Advances in host–guest self-assembled carriers have demonstrated the design of responsive drug delivery systems. Stimuli-triggered architectures—formed by grafting cyclodextrin onto linear or branched polymers—enable precise control of payload release under pH, redox or enzymatic triggers. Studies of polyrotaxane and nanosponges showcased prolonged circulation times, enhanced tumour accumulation and reduced off-target toxicity. Integration of cyclodextrin complexes into diagnostic imaging agents has further illustrated multifunctional platforms that combine therapy and monitoring. Collectively, these developments underline the versatility of cyclodextrin complexation in addressing solubility challenges, improving pharmacokinetics and creating smart drug carriers for next-generation therapeutics.

Cyclodextrin Complexation in Pharmaceutical Systems publication trend

The graph below shows the total number of articles in cyclodextrin complexation in pharmaceutical systems across all publications each year (not limited to Nature Index journals).

Technical terms

Inclusion complex: A non-covalent assembly in which a guest molecule occupies the internal cavity of a cyclodextrin host.

Hydrophobic cavity: The non-polar interior region of cyclodextrin that accommodates lipophilic drug moieties.

Host–guest interaction: Reversible binding between a macrocyclic host and a molecular guest via van der Waals forces, hydrogen bonding and hydrophobic effects.

Derivative: A cyclodextrin molecule chemically modified at its hydroxyl groups to alter solubility, binding affinity or other functional properties.

Stimuli-responsive assembly: A supramolecular structure engineered to release its payload upon exposure to specific triggers such as pH, temperature or enzymes.

References

1. Solubility of Cyclodextrins and Drug/Cyclodextrin Complexes. Molecules (2018).
2. Recent Advances in Host–Guest Self‐Assembled Cyclodextrin Carriers: Implications for Responsive Drug Delivery and Biomedical Engineering. Advanced Functional Materials (2020).
3. Cyclodextrin–Drug Inclusion Complexes: In Vivo and In Vitro Approaches. International Journal of Molecular Sciences (2019).
4. Cyclodextrin-based nanosponges as drug carriers. Beilstein Journal of Organic Chemistry (2012).
5. Cyclodextrins and ternary complexes: technology to improve solubility of poorly soluble drugs. Brazilian Journal of Pharmaceutical Sciences (2011).
6. Cyclodextrins: Structural, Chemical, and Physical Properties, and Applications. Polysaccharides (2021).