Additive Manufacturing and Surface Modification of Biomaterials using Selfassembled Monolayers - Biointerfaces: Where Material Meets Biology - page 41

uneven release of the drug material were reported as some of the major
problems with surface modified DES. 56 Also, implants coated with con-
ventional coating techniques have drawbacks including surface hetero-
geneity in the type and distribution of functional groups, hydrophilic and
hydrophobic domains and surface roughness. 57 Thus a coating technique
that offers precise control on the location and orientation of chemical
groups/biomolecules on the surface is essential to cater for current needs.
Previous studies have shown the use of SLM to fabricate customised im-
plants; however, there is not much research on modifying the surface of SLM
fabricated parts with drug molecules. Surface modification and functiona-
lisation of the SLM fabricated surface to deliver drugs can potentially reduce
post-implant complications and deliver therapeutics on-site.

d n 3 r 4 n g | 0

2.3.2 Surface Modification Using Self-assembled Monolayers
Self-assembled monolayers (SAMs) are ordered molecular assemblies with a
head group, a spacer and a functional tail group as represented in Figure 2.6.
Usually, the head group is bound to a surface and the tail group presents a
chemical functional group. The head and tail groups are separated by a
spacer which is generally an alkyl chain (-CH 2 ). SAM coatings are usually
nano-sized adding only 1-10 nm thickness to the implant surface. 58 This
organic interface provides well-defined thickness and acts as a physical
barrier. SAMs can be designed at molecular level to be biologically inert or
active by modifying the tail group with desired functionality.
SAMs are inexpensive and their ease of functionalisation with well-ordered
arrays of SAMs makes them ideal systems for various applications such
as the control of wetting and adhesion, chemical resistance and nano-
fabrication. 59-61

.

SAMs have wide applications in the healthcare industry

Figure 2.6 Schematic diagram of a single crystalline alkanethiol SAM formed on a

metal surface.