Monday Article #41: Antimicrobial and anticancer activities of Achatina fulica snail mucus
Snail mucus, probably due to its slimy and sticky nature, are often regarded as repulsive and nauseating. However, there has been a growing appreciation towards these slimy substances secreted by snails for its variety of components beneficial towards human health and welfare.
Figure 1. Image of Giant African snail, Achatina fulica .
Achatina fulica, also known as the Giant African snail, is widely available in tropical and subtropical areas due to increased mobility of humans and globalisation of travel and trade . The snail secretes a viscous, sticky mucus that serves various functions, including lubrication, hydration, and blocking of pathogens, throughout the snail’s life. The mucus has long been incorporated into skin and cosmetic products due to its composition of glycoproteins, hyaluronic acid, and glycolic acid. Besides from the cosmetic benefits of the snail mucus, researchers believe that the components of the mucus, such as proteins and amino acids, may also be able to assist in bio-reduction and bio-stabilization steps involved in metallic nanoparticles synthesis.
Silver nanoparticles have been applied in anti-inflammatory therapies and molecular diagnostics. However, it is notable that the silver nanoparticles can be used to combat the problem of multi-drug resistant pathogenic diseases since nanoparticle-based methods will not exert evolutionary pressure on bacteria  and are highly specific towards target organisms . Hence, researchers have presented biogenically synthesised silver nanoparticles in snail mucus matrix (AgNPs-SM).
Upon assessment of the antimicrobial activity of the biogenic silver nanoparticles on both Gram-negative and Gram-positive bacteria displayed clear zones of inhibitions, with no zone of inhibition in the controls, suggesting that the antibacterial activity is due to the nanoparticles alone . In addition, upon comparison of the silver nanoparticles in mucus matrix with a standard antibiotic (ciprofloxacin), it was observed that the nanoparticles-mucus matrix displayed better antimicrobial activity against various bacteria, including S. aureus, P. aeruginosa and E. coli.
Figure 2. Antimicrobial activity of AgNPs-SM against (a) Klebsiella pneumoniae (b) Escherichia coli (c) Pseudomonas aeruginosa (d) Staphylococcus aureus. In each plate, (1) AgNO3, (2) Ciprofloxacin/ Clotrimazole, (3) 25 µg of Ag NPs, (4) 50 µg of Ag NPs, (5) 75 µg of Ag NPs and (6) A. fulica mucus were added, respectively .
As seen in the table below, better antimicrobial activity can be seen for the silver nanoparticle-mucus matrix (AgNP-SM), observed by larger zones of inhibition, as compared to ciprofloxacin. Hence, researchers believe that the AgNPs-SM, a combination of broad-spectrum antimicrobial silver nanoparticles and skin benefiting ingredients of snail mucus, can be applied for the treatment of a widely prevalent bacterial skin disease — acne. The snail mucus is able to rejuvenate the skin and reduce the development of acne scars through hydration of the dermis and its collagen regulating properties . Besides that, extended periods of antibiotic application often confer resistance of the acne towards these treatments, whereas silver nanoparticles are expected to not have the problem of resistance development. Therefore, AgNPs-SM based formulations have the potential to be developed into topical gels or creams for rapid wound healing and acne treatment.
Table 1. Zone of inhibition and MIC of silver nanoparticles synthesised in A. fulica mucus matrix .
In addition to the antimicrobial activities of the silver nanoparticle-mucus matrix (AgNP-SM), the nanoparticles were also found to display cytotoxic activity. The cytotoxicity of the matrix led to more than 15% inhibition of HeLa cells, which are derived from cervical cancer cells, upon investigation. As the concentration of the Ag-NP increased, the inhibition activity towards the cancer cells also rose. The nanoparticle-mucus composites are not only able to stimulate apoptosis, but they are also able to specifically recognize the cancer cells . Additionally, a significant increase in inhibition of cell viability and proliferation of HeLa cells can be seen when anticancer agents are combined with AgNPs through alteration of cellular signalling molecules involved in cytotoxicity and apoptosis . In other studies conducted, anticancer agents coated silver nanoparticles led to a rise in cell mortality rates , demonstrated toxicity against MCF7 and T47D breast cancer cell lines , and displayed cell-specific toxicity against human lung cells .
Apart from the assistance in bio-reduction and bio-stabilization steps involved in metallic nanoparticles synthesis, the mucus of Achatina fulica also displayed antimicrobial activities on both Gram-negative and Gram-positive bacteria. The silver nanoparticle-mucus matrix’s (Ag-NPs) antimicrobial activities and lack of resistance development towards metallic nanoparticles makes them a promising candidate for acne treatment formulations. Besides the utilizations mentioned above, the Ag-NPs also demonstrated significant inhibition of cancer cell lines as well as anticancer activities. Hence, snail mucus, such as those of Achatina fulica, carries great potential for developing products greatly beneficial to humanity.
 Giant African land snail (Achatina fulica) [Online image]. (2016). Retrieved 29 December, 2022 from https://commons.wikimedia.org/wiki/File:Giant_African_land_snail_%28Achatina_fulica%29.jpg
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This article was prepared by Phoebe Tee Yon Ern