Abstract
We report on ultraviolet (UV) light induced increases in the UV optical density of thin and optically transparent crystalline DNA films formed through self assembly. The films are comprised of closely packed, multi-faceted and sub micron sized crystals. UV-Vis spectrophotometry reveals that DNA films with surface densities up to 0.031 mg/mm2 can reduce the transmittance of incident UVC and UVB light by up to 90%, and UVA transmittance by up to 20%. Subsequent and independent film irradiation with either UVA or UVB dosages upwards of 80 J/cm2 both reduce UV transmittance, with reductions scaling monotonically with UV dosage. To date the induction of a hyperchromic effect has been demonstrated using heat, pH, high salt mediums, and high energy ionising radiation. Both hyperchromicity and increased light scattering could account for the increased film optical density after UV irradiation. Additional characterisation of the films reveal they are highly absorbent and hygroscopic. When coated on human skin, they are capable of slowing water evaporation and keeping the tissue hydrated for extended periods of time.
Highlights
Deoxyribonucleic Acid (DNA) is a long chain biopolymer that has been studied extensively in order to understand its relevance to human health
This research has revealed the impact of UV-light, magnetic fields and fluid surface tension on the resultant DNA film structure
We demonstrate that similar increases in the optical density of thin, self assembled DNA films can be induced through irradiation with sufficient dosages of non-ionising UVB (Fig. 5) and UVA (Fig. 6) light
Summary
Deoxyribonucleic Acid (DNA) is a long chain biopolymer that has been studied extensively in order to understand its relevance to human health. UVC and vacuum-UV are fully attenuated by Earth’s atmospheric gases[6, 12, 13] and studies have shown only limited evidence of UVC carcinogenicity in humans[14]. Both UVB and UVA have been associated with increased risk of skin cancer[15]. Incidences of cutaneous malignant melanoma, squamous cell carcinoma and basal cell carcinoma increase with ambient exposure to UV light[6] Due to their combined presence in solar light the relative contribution of UVA and UVB light to DNA photodamage continues to be a topic of debate[1, 7, 10, 16,17,18,19,20]. Additional swelling and evaporation kinetics of films coating human stratum corneum skin tissue are quantified to further characterise their structure and hygroscopic properties
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