## 2 Materials and Methods
### Determination of Antibacterial and Antifungal Activity of the of TiO\({}_{2}\)-NT Surfaces  
A panel of microorganisms composed of an equal amount of three Gram-negative bacteria Escherichia _coli_ ATCC\({}^{\circledR}\) 8739\({}^{\text{TM}}\), _Pseudomonas aeruginosa_ ATCC\({}^{\circledR}\) 9027\({}^{\text{TM}}\) and _Brevundimonas diminuta_ ATCC\({}^{\circledR}\) 19146\({}^{\text{TM}}\), three Gram-positive bacteria composed of _Bacillus subtilis_ subsp. _spizizizeni_ ATCC\({}^{\circledR}\) 6633\({}^{\text{TM}}\), _Staphylococcus epidermidis_ ATCC\({}^{\circledR}\) 12228\({}^{\text{TM}}\) and _Staphylococcus aureus_ ATCC\({}^{\circledR}\) 12600\({}^{\text{TM}}\), two yeast cultures composed of _Candida albicans_ ATCC\({}^{\circledR}\) 10231\({}^{\text{TM}}\) and _Saccharomyces cerevisiae_ ATCC\({}^{\circledR}\) 9763\({}^{\text{TM}}\), and three fungal cultures composed of _Aspergillus brasiliensis_ (niger) ATCC\({}^{\circledR}\) 9642\({}^{\text{TM}}\), _Cryptococcus albidus_ ATCC\({}^{\circledR}\) 34140\({}^{\text{TM}}\) and _Penicillium chrysogenum_ ATCC\({}^{\circledR}\) 10106\({}^{\text{TM}}\) were all purchased as certified Culti-Loops from Thermo Scientific\({}^{\text{TM}}\) Oxoid\({}^{\text{TM}}\).  
The loops were rehydrated in 50 mL of previously sterilized tryptic soya broth (TSB Oxoid\({}^{\text{TM}}\)). _A. brasiliensis_ and _P. chrysogenum_ were rehydrated in a sterile Sabouraud-dextrose broth (SDB Oxoid\({}^{\text{TM}}\)) supplemented with 0.05% of Tween 80. The addition of Tween 80 prevented the formation of cellular clumps and allowed the formation of single-celled cultures. _C. albidus_ and _A. brasiliensis_ were rehydrated in SDB without Tween 80. All the cultures were incubated with shaking at 37 \({}^{\circ}\)C at 120 rpm for 8 h under aerobic conditions. The microbial suspensions were individually adjusted with broth to 0.5 abs units at 600 nm which corresponded to \(1.5\times 10^{8}\) CFU. The resulting solution was used to test the antimicrobial activity of the coupons at full spectrum UV radiation. A total of 200 \(\upmu\)L of microbial solution was uniformly placed on each coupon through the aid of a micropipette and placed into a climatic chamber (ICH 256 Memmert GmbH) set at 37 \({}^{\circ}\)C and 80% relative humidity. Figure 2 shows the typical experimental setup used. The coupons were placed onto a clean microscope slide and elevated on top of a 5 cm open petri dish [27]. To further prevent the microbial suspension from drying out the petri dish, over which the slide was placed, the petri dish filled with 10 mL of water. After 1 h of irradiation, the microbial solution was transferred into a sterile 5 cm petri dish and 1 mL of sterile 1\(\times\) PBS was added. The contents of the petri dish was mixed gently to ensure that all the bacteria were recovered from the surface of the coupons. The PBS solution was transferred into a sterile microcentrifuge tube and aliquots were taken to prepare a serial dilution ranging from 10\({}^{-2}\)-10\({}^{-6}\). From which 50 uL were taken and plated onto previously prepared plates of total count agar for bacteria and Sabouraud-dextrose agar (SDA Oxoid(tm) Basingstoke, United Kingdom) for yeast and fungi. The plates were incubated upside down for 10-20 h at 35 \({}^{\circ}\)C. The resultant colonies were counted, and the percentage antimicrobial activity of the surface was expressed relative to untreated titanium blank coupons. The experiment was repeated using the same conditions without UV light to ensure that the observed antimicrobial activity could be attributed to the effect of UV light and coupons.