Hypoxia, inflammation and microbial infections, usually associated with Staphylococcus aureus, in particular methicillin-resistant S. aureus (MRSA) strains, are common features of chronic wounds. The limited solubility, short half-life, and variable adsorptions of drugs along with the limited efficacy of transdermal drug delivery are driving the attention towards new therapeutic approaches. The known benefits of nanotechnology combined with the emerging advantages of using natural antimicrobial polysaccharides, such as chitosan, have paved the way to develop nonconventional and innovative adjuvant therapies for infected wounds. Chitosan-shelled oxygenloaded nanobubble (OLNB) and chitosan-shelled oxygen-loaded nanodroplet (OLND) potential, as treatments for infected wounds, was here assessed by investigating their antibacterial activity against MRSA along with toxicity on human keratinocytes. Medium molecular weight (MW) chitosan-shelled OLNBs/OLNDs were prepared and characterized for morphology, size, and avarage diameter. Confocal microscopy analyses was performed to study the physical interaction between OLNBs/OLNDs and cell walls. Cytostatic activity was evaluated by incubating MRSA alone or with 10% v/v OLNBs/OLNDs within 24 h. Toxicity on human skin cells was studied by lactate dehydrogenase assay after incubating HaCaT keratinocytes alone or with 10% v/v OLNBs/OLNDs either in normoxia and hypoxia for 24 h. Both OLNBs and OLNDs adhered on staphylococcal cell walls and showed shortterm (up to 4 h) antibacterial activity against MRSA, due to chitosan presence as antimicrobial compound in the shell. OLNBs, as well as OLNDs were not toxic to keratinocytes, whereas oxygenfree nanobubbles (OFNBs) and oxygenfree nanodroplets (OFNDs) slightly affected hypoxic cell viability, thus suggesting a protective role for oxygen on human skin cells. Nanodroplets are able to release from the core more oxygen than nanobubbles, so we focused attention on this nanocarrier. A new OLND formulation was prepared using low molecular weight (LW) chitosan for the shell manufacturing. Interestingly, LW OFNDs, compared with OFNDs, were not toxic to keratinocytes and LW OLNDs (in contrast with OLNDs and OFNDs), as well LW OFNDs, are internalized by MRSA. Chitosan-shelled OLNBs and OLNDs development has the potential to be a highly innovative, cost-effective and non-toxic product for the concurrent treatment of hypoxic infected tissues. Such treatment could represent an innovative therapy of infected chronic wounds improving the patient quality of life, especially the elderly. Based on these data, future studies on chitosan nanodroplets, especially manufactured with LW chitosan, are heavily encouraged.
ANTIBACTERIAL ACTIVITY OF CHITOSAN-SHELLED OXYGENLOADED NANOBUBBLES AND NANODROPLETS AGAINST MRSA IN CHRONIC WOUNDS
G. Banche;N. Finesso;V. Allizond;M. Prato;A. Luganini;DE TROIA, Anna;G. Giribaldi;A. Khadjavi;V. Tullio;N. Mandras;M. Argenziano;R. Cavalli;C. Guiot;AM Cuffini
2017-01-01
Abstract
Hypoxia, inflammation and microbial infections, usually associated with Staphylococcus aureus, in particular methicillin-resistant S. aureus (MRSA) strains, are common features of chronic wounds. The limited solubility, short half-life, and variable adsorptions of drugs along with the limited efficacy of transdermal drug delivery are driving the attention towards new therapeutic approaches. The known benefits of nanotechnology combined with the emerging advantages of using natural antimicrobial polysaccharides, such as chitosan, have paved the way to develop nonconventional and innovative adjuvant therapies for infected wounds. Chitosan-shelled oxygenloaded nanobubble (OLNB) and chitosan-shelled oxygen-loaded nanodroplet (OLND) potential, as treatments for infected wounds, was here assessed by investigating their antibacterial activity against MRSA along with toxicity on human keratinocytes. Medium molecular weight (MW) chitosan-shelled OLNBs/OLNDs were prepared and characterized for morphology, size, and avarage diameter. Confocal microscopy analyses was performed to study the physical interaction between OLNBs/OLNDs and cell walls. Cytostatic activity was evaluated by incubating MRSA alone or with 10% v/v OLNBs/OLNDs within 24 h. Toxicity on human skin cells was studied by lactate dehydrogenase assay after incubating HaCaT keratinocytes alone or with 10% v/v OLNBs/OLNDs either in normoxia and hypoxia for 24 h. Both OLNBs and OLNDs adhered on staphylococcal cell walls and showed shortterm (up to 4 h) antibacterial activity against MRSA, due to chitosan presence as antimicrobial compound in the shell. OLNBs, as well as OLNDs were not toxic to keratinocytes, whereas oxygenfree nanobubbles (OFNBs) and oxygenfree nanodroplets (OFNDs) slightly affected hypoxic cell viability, thus suggesting a protective role for oxygen on human skin cells. Nanodroplets are able to release from the core more oxygen than nanobubbles, so we focused attention on this nanocarrier. A new OLND formulation was prepared using low molecular weight (LW) chitosan for the shell manufacturing. Interestingly, LW OFNDs, compared with OFNDs, were not toxic to keratinocytes and LW OLNDs (in contrast with OLNDs and OFNDs), as well LW OFNDs, are internalized by MRSA. Chitosan-shelled OLNBs and OLNDs development has the potential to be a highly innovative, cost-effective and non-toxic product for the concurrent treatment of hypoxic infected tissues. Such treatment could represent an innovative therapy of infected chronic wounds improving the patient quality of life, especially the elderly. Based on these data, future studies on chitosan nanodroplets, especially manufactured with LW chitosan, are heavily encouraged.
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