Curcumin halloysite nanoformulation with selective antimicrobial effects

(Nanowerk Spotlight) Turmeric (Curcuma longa L.) has a long history of usage in traditional medicine in India and China. Ancient Indians have known the medicinal properties of turmeric – i.e. curcumin – for several millennia.
Curcumin, a hydrophobic natural pigment, appears to have a unique ability to work through many different pathways with its extraordinary attributes (read more: "Nanotechnology-enhanced curcumin: Symbiosis of ancient wisdom with modern medical science" and, if you really are into details, this: "Nanotechnology-enhanced curcumin – literature and patent analysis").
In the scientific literature there is a large body of evidence showing that curcuminoids exhibit a broad spectrum of biological and pharmacological activities including anti-oxidant, anti-inflammatory, anti-bacterial, anti-fungal, and anti-parasitic properties – although some of its claimed effects (particularly as an anticancer drug) have not been convincingly confirmed yet.
"A major issue with curcumin is its low bioavailability due to its hydrophobicity," Rawil Fakhrullin, a Professor in the Bionanotechnology Group at the Institute of Fundamental Medicine and Biology, Kazan Federal University (Republic of Tatarstan, RF), tells Nanowerk. "In our recent work on antimicrobial effects of curcumin we used halloysite as a means to increase its bioavailability."
Halloysite is a natural biocompatible nanomaterial available in thousands of tons at low price, which makes it a good candidate for nanoarchitectural composites. In vitro and in vivo studies indicate the safety of halloysite. Furthermore, it can store and release molecules in a controllable manner, making these tiny containers attractive for applications in various applications ranging from polymer and concrete additives to antimicrobial coatings and biomedical drug delivery vehicles (see our Nanowerk Spotlight on the controlled release of nanohydrogel from halloysite nanotubes).
While there have been previous research reports on halloysite loading with curcumin via covalent tailoring, Fakhrullin's team, working in collaboration with Prof. Giuseppe Lazzara from the University of Palermo, selected a different strategy based on physical adsorption followed by polymer capping.
halloysite nanotubes pristine and as nanoformulation
Scanning electron microscopy images of a) pristine, b) curcumin-loaded halloysite nanotubes and c) HNTs+Curc/DX nanocontainers. (Reprinted with permission by American Chemical Society) (click on image to enlarge)
As the team reports in ACS Applied Materials & Interfaces ("Selective antimicrobial effects of [email protected] nanoformulation: a Caenorhabditis elegans study"), thermogravimetry and spectroscopy studies show that this approach allows for better loading and more effective release of curcumin in vivo.
The researchers used Caenorhabditis elegans nematodes as a model to investigate the antibacterial effects of curcumin loaded into halloysite clay nanotubes. They coated the external surface of the curcumin-loaded halloysite nanotubes with dextrin, which allowed for the intestinal release of curcumin.
The composite nanotube/prodrug containers were successfully used to suppress the pathogenic (for C. elegans) Serratia marcescens bacteria, while not affecting Escherichia coli bacteria that were administered as nematode food.
The curcumin-loaded halloysite nanoformulation drastically increased the life expectancy of nematodes infected by the pathogenic bacteria.
As Fakhrullin points out, the most interesting finding in this paper is the selective antimicrobial action of curcumin, which suppressed one bacterial species, while demonstrating no adverse effect on another.
"We believe that our procedure to encapsulate hydrophobic drugs into halloysite nanotubes will be helpful in fabricating antimicrobial formulations capable of effective treatment of microbial imbalance and selective suppression of microbiota," he notes. "We now need to find out if the procedure we reported is universal and applicable to other hydrophobic antimicrobial materials targeting other microorganisms relevant to humans."
Against the backdrop of the growing threat of antibiotic-resistant bacteria, a particularly interesting aspect of this work is the idea to selectively control microbial growth using natural compounds other than antibiotics.
By Michael is author of three books by the Royal Society of Chemistry:
Nano-Society: Pushing the Boundaries of Technology,
Nanotechnology: The Future is Tiny, and
Nanoengineering: The Skills and Tools Making Technology Invisible
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