Bacterial nanocellulose with a shape-memory effect as potential drug delivery system

Abstract

In the steadily emerging field of applications for the natural biopolymer bacterial nanocellulose (BNC), the development of environmentally-friendly and cost-saving techniques to form xerogels by partial or complete dewatering is of great interest for convenient storage, handling and a reduced risk of microbial contamination. Air-dried BNC itself is not able to rehydrate after complete drying due to a structural collapse. In the present paper, it was supplemented with different hydrophilic, water-binding additives and characterized regarding morphology, re-swelling behavior, mechanical stability and potential as drug delivery system. A fast rehydration could be obtained by the addition of magnesium chloride > glucose > sucrose > sorbitol, with a maximum re-swelling percentage up to about 88% (magnesium chloride) of the initial wet weight. In contrast, poly(ethylene glycol) (8 kDa), lactose and trehalose reached only 12-30% whereas mannitol and sodium chloride only had a negligible effect. A high re-swelling value was found to be correlated with the preservation of the three-dimensional BNC network structure and mechanical characteristics such as compression and tensile strength. Confirming the relevance of these findings, the use of the hydrophilic model drug azorubine demonstrated the applicability of the shapememorized bacterial nanocellulose as drug delivery system with controllable release profiles.

Nanocellulose as a natural source for groundbreaking applications in materials science: Today’s state

“…This is of importance for applications of BNC hydrogels as medical implants [28]. Another method of brittleness prevention is the post-modification of BNC with selected additives like inorganic salts or polyalcohols which results not only in a fast reswelling behavior (so called shape-memory effect) after air-drying but also in more flexible storage forms [29].…”

“…Three categories of nanocellulose materials have been described as drug carriers: planar hydrogels (fleeces, films, membranes, coatings) [410][411][412][413], CNFs [414,415] as well as CNCs [416][417][418][419], with the two latter preferentially formulated as nano-and microparticles, gels, or suspensions [9]. For the entrapment of drugs these materials were used in the wet native [37,420,421], dried (freeze-dried, critical point dried) [422] or semi-dried [413,423] form, as well as air-dried materials with a shape memory effect [29,424]. After freeze-drying of BNC uptake and release of drugs (e.g., albumin) were found to be reduced due to changes of the fiber network [425], which is why often semidried matrices were preferred.…”

Dynamics of Hydration of Nanocellulose Films

“…[9][10][11][12][13] Hydrogels, a cross-linked polymer in contact with an aqueous environment, are among the most investigated materials because of their ease of fabrication and large tunability of their properties and are used to translate a chemical signal into a mechanical output in the form of a reversible change of the gel volume. [ 14,15 ] The swelling of the hydrogel might be used to induce a further action, for example to bend microstructures [ 16 ] or to create autonomous self-oscillating systems. [ 17 ] Other natural examples of such actuation can be found in vegetables and can be used to design artifi cial analogous with a predetermined mechanical behavior.…”

Thermal properties of nanocellulose‐reinforced composites: A review

“…, with permission from Elsevier), and (c) BNC (reproduced from ref. , with permission from The Royal Society of Chemistry).…”