Interfaces in Composite Materials - Biointerfaces: Where Material Meets Biology - page 163

Biologically inspired, self-healing composites, based on incorporation of
reactive fillers (e.g., monocalcium phosphate monohydrate and b-tricalcium
phosphate) within a degradable polymer matrix, have been developed as
bone adhesives/cements. Upon water sorption, these fillers undergo chem-
ical reaction to form a new phase (e.g., brushite). The resultant phase oc-
cupies greater volume than the starting phases and potentially fills the
cracks/defects produced within the composite. 99-103 Step-by-step prepar-
ation of this example of self-healing composites will be described in detail
later in this chapter.

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7.3.3 Composites Based on Smart Fillers
Inorganic nanoparticles with diversified functionalities and self-assembling
ability could be a material for future biomedical use. Self-assembly of
nanoparticles enables flexible design of materials with different microscopic
and macroscopic architectures. Composites containing Raman-active
nanoparticles, for example, could be used as ultrasensitive molecular de-
tection and imaging platform e.g., rhodamine 6G (R6G). 104 Composites with
diverse set of on-demand properties, e.g., regions of variable expansion,
conductivity and strength properties, have also been produced by in-
corporating various fillers into a single flexible polymer matrix. Applications
include bioelectronics and sensors. Inclusion of microfluidic channels, that
can expand on demand, within the flexible matrix extends the application of
these composites for live analysis of captured rare cells, e.g., circulating
tumor cells. 105 Composites with anti-bacterial properties have also been
produced by plasma grafting of anti-bacterial nanoparticles onto a polymer
matrix. 106 Various smart, anti-cariogenic, pH-responsive, dental nano-
composites have been prepared by incorporating different calcium phosphate
fillers (e.g., amorphous calcium phosphate, nano-tetracalcium phosphate,
mixture of mono-calcium phosphate monohydrate and b-tricalcium phos-
phate). Under acidic conditions, these composites release Ca and PO 4 . The
released species have the ability to neutralize the acidity produced by cario-
genic bacteria, stop caries, and re-mineralize dental lesions. 107-110

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7.3.4 Functionalized Composites
Designing new functional materials with tailored physical and chemical
properties as well as versatile and reliable processing capabilities represents
a great challenge in modern materials science. Cell adhesion is a pre-
requisite for other cellular activities. 65 Introducing nano-scale surface
topography on biomaterials 74 can therefore mediate adsorption of cell
adhesive proteins, e.g., fibronectin, 111 which are necessary for cell adhesion.
Hierarchically organized nano-structured composites can be fabricated
via nano-imprint lithography, 112 photo-imprinting 72 and atomic layer

deposition. 113