Additive Manufacturing and Surface Modification of Biomaterials using Selfassembled Monolayers - Biointerfaces: Where Material Meets Biology - page 50

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Figure 2.12 Surface wettability of SLM fabricated parts before SAM attachment (a);

after SAM attachment (b) and after drug attachment (c).

Figure 2.13 Steps antibacterial susceptibility test against (a) S. aureus and (b) E. coli.

Label description: C, control disc with no drug; CD, control with drug
on; TC, discs coated with Tris-HCl buffer; 1, 2, 4, 6, immersion time
intervals (in weeks) of the samples in buffer solution.

.

Drug estimation was performed using a base hydrolysis method. 52 Drug
coated samples (n ¼ 5) were immersed in a 10 mM NaOH solution of pH

9
and incubated for 2 weeks to hydrolyse the drug attached to SAMs. The drug
eluted solution was adjusted to pH 7.4 using 1 M HCl. A UV-visible spec-
trophotometer was used to estimate the drug eluted. A calibration curve was
plotted for the working solution of ranges 1 ng mL 1 to 1 mgmL 1 in 10 mM
NaOH of pH

B

7.4. Using this calibration curve, the total amount of drug
coated was estimated to be approximately 1 mgcm 2 .
Tests to measure oxidative stability (by exposing the drug coated surface to
atmosphere) and in-vitro stability (by immersing the drug coated surface in
10 mM of Tris-HCl buffer solution (pH

B

7.4) were performed. These studies
revealed the drug coated surfaces were highly stable under oxidative con-
dition whereas, under in-vitro conditions, the drug was observed to release in
a sustained manner. After 6 weeks of immersion in Tris-HCl buffer, nearly
40% of the drug was observed to remain attached to the SAMs coated on the
SLM fabricated surface. On performing an anti-bacterial susceptibility test
with Gram-positive (Staphylococcus aureus) and Gram-negative bacteria
(Escherichia coli), the discs coated with the drug showed anti-bacterial ac-
tivity, confirming the drug was active upon its release (Figure 2.13).

B