Enhancement of the Antibacterial Activity of Natural Rubber Latex Foam by Blending It with Chitin

Zhang, Nanxi

doi:10.3390/ma13051039

Cited by 28 publications

(23 citation statements)

References 51 publications

(53 reference statements)

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“…Organic biomaterials like chitin, an essential component of the cell walls of fungi (Lenardon et al, 2010), and used in insect exoskeletons and jaws, could add to the strength of the outer layer of a propagule of Martian life, such as a fungus. Chitin has a Mohs hardness of 7 -7.5 (Zhang et al, 2020) similar to quartz (King, n.d.). Chitin nanofibers have a Young's modulus of elasticity of more than 150 GPa (Vincent et al, 2004), higher than copper or titanium alloy and not far below wrought iron or steel (Engineering ToolBox, 2003).…”

Section: Figure Needs Permission]mentioning

confidence: 99%

NASA and ESA are likely to be legally required to sterilize Mars samples to protect the environment until proven safe – the technology doesn't yet exist to comply with the ESF study's requirement to contain viable starved ultramicrobacteria proven to pass through 0.1 micron nanopores - proposal to study samples of astrobiological interest remotely in a safe high orbit above GEO with miniature life detection instruments – and immediately return sterilized subsamples to Earth

Walker¹

2021

Preprint

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NASA plans to return samples from Mars by 2031. They believe that there is no surface life in Jezero crater but astrobiologists can’t yet rule out surface microhabitats, where life might survive from a more habitable early Mars. NASA agrees it needs to protect Earth from the possibility of native Martian life in the samples.Most of our laws to protect Earth’s biosphere didn’t exist in 1969. The Apollo sample returns had no legal review. With many lapses of containment, they are now seen as an example of how not to protect Earth.NASA's proposal will get careful scrutiny. We find that this may change build requirements. The sample return study by the European Space Foundation from 2012 requires 100% containment of starvation stressed nanobacteria. These pass through 0.1 micron nanopores, far beyond the limits of testing for HEPA or ULPA filters. If this becomes a legal requirement, the technology doesn't yet exist, even as experimental filters in laboratories.NASA is not permitted to risk such a high level of public funds (~$500 million), until they know if their proposed design will be accepted or modified. The requirements could change through to the end of the legal process of 8+ years. Adding 11+ years for the build, we find that NASA won't be ready for unsterilized samples from Mars before 2039 with delays likely.It's possible to sterilize samples at a level sufficient for planetary protection while preserving astrobiological and geological interest. This becomes an unrestricted sample return; a relatively simple process under the Outer Space Treaty.However, there may be interest in the possibility of viable present day life in the samples. If so, we propose NASA return them to a holding satellite in a stable inclined orbit above GEO in Earth's Laplace plane or "ring plane". This particular orbit has many advantages for protection of Earth, the Moon, and other satellites. Sterilized subsamples can be returned to Earth immediately, so there's no delay for geological studies. If the unsterilized samples are of astrobiological interest, scientists can study them from Earth, teleoperating instruments already designed to search for life in situ on Mars, but with almost no latency. We can decide what to do next based on what they discover.This article examines specific worst case scenarios, such as a blue-green algae with everything flipped as in a mirror: DNA spirals the other way; amino acids, carbohydrates, sugars, all are in their mirror forms. A mirror cell should function identically to a normal cell but most ordinary terrestrial life can't make any use of its mirror organics.Synthetic biologists have started a step by step process to flip a terrestrial cell of normal life to mirror life. They warn that such life, if released from the lab, could gradually transform organics in terrestrial ecosystems to indigestible mirror organics giving it a competitive advantage over terrestrial life.To keep Earth safe, synthetic mirror cells will depend on chemicals only available in the laboratory. We might have to leave any Martian mirror life in orbit to achieve a similar level of safety.In the worst case scenarios Mars's biosphere can never mix safely with Earth's. Sometimes quarantine of returning astronauts is also insufficient to protect our biosphere. In other scenarios Martian life is harmless.Future possibilities, and opportunities, open to us depend on whether there is life on Mars and what it's like. Answering this seems a top priority for space colonization enthusiasts and astrobiologists alike.With a combined effort, astronauts could conduct rapid surveys of the most important potential habitats from orbit around Mars, via telepresence. Humans in orbit could control surface robots with minimal latency. This would help resolve these questions as fast as possible.We also suggest that the ESA fetch rover is modified to return a sample of dirt, including the brine layers discovered by Curiosity, to resolve the puzzling Viking lander results. Are these the result of complex chemistry or native life? We also suggest collecting some of the dust to study whether terrestrial microbes could propagate in dust storms and to start a search for dust storm resistant Martian propagules.There is no other terrestrial planet within reach, to study chemical processes on a planet left for billions of years without life. If the apparent circadian rhythms in the Viking experiment are due to complex chemistry, could this be relevant to understanding the chemistry of planets before the first living cells?This mission can easily miss present day life even if it exists in the region explored by Perseverance. However, we can maximize chances of success. Whatever we detect is a useful first step to inform future searches.This article concludes that the complex laws already in place to protect Earth’s biosphere are both understandable and necessary.

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Section: Figure Needs Permission]mentioning

confidence: 99%

NASA and ESA are likely to be legally required to sterilize Mars samples to protect the environment until proven safe – the technology doesn't yet exist to comply with the ESF study's requirement to contain viable starved ultramicrobacteria proven to pass through 0.1 micron nanopores - proposal to study samples of astrobiological interest remotely in a safe high orbit above GEO with miniature life detection instruments – and immediately return sterilized subsamples to Earth

Walker¹

2021

Preprint

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“…The effect of CaCO 3 on hardness is shown in Figure 2a. The hardness (Shore C) mainly describes the ability of the rubber to resist pressing [19]. Figure 2a shows the hardness of the CaCO 3 -filled NRLF at different CaCO 3 loadings.…”

Section: Physical Characteristics Hardness and Densitiesmentioning

confidence: 99%

Combination Effects of Calcium Carbonate and Crumb Rubber Fillers on the Properties of Natural Rubber Latex Foams

Rattanapan

Artchomphoo

Saijun

et al. 2021

Curr. Appl. Sci. Technol.

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The preparation and mechanical properties of natural rubber latex foam (NRLF) using calcium carbonate (CaCO3) or combinations of CaCO3 and crumb rubber (CRM) as fillers were investigated. The CaCO3 contents were varied as 10, 20, and 30 phr. The ratios of CaCO3/CRM at 0.5/1.0, 0.75/0.75 and 1.0/0.5 were used. The experimental findings were that CaCO3 was well dispersed and blended with the natural rubber latex. The density of the NRLF increased with the increase in CaCO3 content. The foam containing less than 20 phr of CaCO3 showed higher tensile strength and elongation at the break than natural rubber latex foam without CaCO3. The percentage of compression set and depression of NRLF increased with increasing CaCO3 content. When the mixture of CaCO3 and CRM was used as a filler in NRLF, it was found that both CaCO3 and CRM were well dispersed and mixed with natural rubber latex. The NRLF containing the mixture of CaCO3 and CRM was more flexible than the foam containing only CaCO3. Furthermore, the NRLF with CaCO3 and CRM at the ratio of0.75/0.75 showed more uniform bubble shape and higher density than foam with other CaCO3/CRM ratios. The tensile strength of the foam decreased with decreasing CRM content, while the percentage of depression was low when the proportion of the CRM was reduced. Furthermore, the foam containing CaCO3/CRM ratio of 0.75/0.75 showed the lowest compression set.

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“…An antimicrobial agent is a natural or synthetic substance that can kill or inhibit the growth of microorganisms by disrupting the essential microbial metabolic pathway or changing the cell membrane or cell wall structure [ 19 ]. There are a wide variety of antimicrobial agents that have proven their antimicrobial activities in NR latex, such as chitin [ 20 ], mangosteen peel powder [ 21 , 22 ], zinc oxide nanoparticles [ 23 , 24 ], silver nanoparticles [ 25 ], vegetable oil emulsion [ 26 ], and povidone-iodine [ 27 ]. Each antimicrobial agent has its mechanism for suppressing the growth of pathogenic microorganisms.…”

Section: Introductionmentioning

confidence: 99%

Natural Rubber (NR) Latex Films with Antimicrobial Properties for Stethoscope Diaphragm Covers

Azura

2022

Materials

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Systematic disinfection of the stethoscope diaphragm is required to ensure that it does not act as a vector for cross-transmission of health-related diseases. Thus, an antimicrobial latex film could be used as a cover to inhibit pathogenic bacteria from growing on its surface. The aim of this work is to determine the antimicrobial activity and mechanical properties of antimicrobial natural rubber (NR) latex films with different types of antimicrobial agents (mangosteen peel powder (MPP), zinc oxide nanoparticles (ZnO NP), and povidone-iodine (PVP-I)). The antimicrobial loading was varied from 0.5, to 1.0, and 2.0 phr to monitor the effective inhibition of Gram-negative bacteria and fungi growth. For MPP and PVP-I antimicrobial agents, a loading of 2.0 phr showed good antimicrobial efficacy with the largest zone of inhibition. Simultaneously, ZnO NP demonstrated excellent antimicrobial activity at low concentrations. The addition of antimicrobial agents shows a comparable effect on the mechanical properties of NR latex films. In comparison to control NR latex film (29.41 MPa, 48.49 N/mm), antimicrobial-filled films have significantly greater tensile and tear strengths (MPP (33.84 MPa, 65.21 N/mm), ZnO NP (31.79 MPa, 52.77 N/mm), and PVP-I (33.25 MPa, 50.75 N/mm). In conclusion, the addition of antimicrobial agents, particularly ZnO NP, can be a better choice for NR latex films because they will serve as both an activator and an antimicrobial. In a clinical context, with regard to frequently used medical equipment such as a stethoscope, such an approach offers significant promise to aid infection control.

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Enhancement of the Antibacterial Activity of Natural Rubber Latex Foam by Blending It with Chitin

Cited by 28 publications

References 51 publications

Combination Effects of Calcium Carbonate and Crumb Rubber Fillers on the Properties of Natural Rubber Latex Foams

Natural Rubber (NR) Latex Films with Antimicrobial Properties for Stethoscope Diaphragm Covers

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