1.2.1 Hydroxyapatite (HAp)
HAp chemical nature is calcium phosphate and it is retrieved from varied
sources which includes mammalian sources such as bone from camel,
bovine, horse, marine sources like fish scale, shells, marine plants,
algae, and mineral sources. Certain red algal forms such asPhymatolithon calcareum (Kusmanto et al., 2008), Amphiroa
ephedra (Oliveira et al., 2007) have calcium carbonate in their
structure and are precursors of Hap.
Hydroxyapatite is a biocompatible, porous, renewable and bioactive
polymer and has been used as bone filler material. HAp can be mixed with
a polycaprolactone to manufacture mechanically strong and porous
scaffolds. Hydroxyapatite prepared from aquatic sources is thermostable
at higher temperatures of 1200°C (Piccirillo et al., 2013).
Hydroxyapatite (HAp) provides efficient absorption surface for
functional biomolecules such as protein, DNA and so on and it influences
the HAp surface electronic state. Surface electrical properties of HAp
such as resistivity and capacitance can be useful as receptors and
transducers of biosensors.
1.2.2. Marine
Calcium carbonate (CaCO3 or calcite):
Calcite is a precursor molecule for hydroxyapatite and isolated from
different marine corals (Lithothamnion glaciale , Coralline
officinallis, and Phymatholithon calcareum ), calcifying algae,
sponges, echinoderms, foraminifera, mollusks (Ostrea sdulis,
Pinctada maxima, Mytilus galloprovincialis ) bryozoans, fish bones, and
Crustaceans shells (Andersson & Gledhill, 2013). Calcite has a
resemblance to trabecular bones and suitable for orthopedics and
dentistry (Srivastava et al., 2015). It has an advantage of porosity and
pore interconnectivity as well as a demerit of fast dissolution and poor
structural stability (Ben-Nissan, 2003).
1.2.3. Biosilica:
Biosilica is formed by biomineralization of silica known as frustules
and formed by sponges, diatoms, radiolarians, and choanoflagellates
(Schröder et al., 2008). The silica frustule structure varies in diatom
species. There are approximately 3000 species of diatoms with silica
exoskeleton. Some of them are Aulacoseria ambigua ,stephanodiscus minutulus , Melosira undulata, andCocconeis placentula .
Diatom silica has advantages of
high surface area, porous, chemically inert, biocompatible,
thermomechanical stability, lightweight, optophotonics features and it
acts as ideal biomaterial for tissue designing, drug deliverables, and
biosensors. The addition of various metals in silica frustules improves
its physiochemical attributes as nanomaterial.
Delasoie and Zobi (2019) revealed the application of biosilica frustule
of genera Aulacoseira graulata as drug delivery vehicles to
colorectal cancer cells. Other diatom species such asThalassiosira weissflogii, Coscinodiscus concinnus, Thalassiosira
pseudomonas and Nitzschia species also can deliver drugs andPhaeodactylum tricornutum, and Odontella are considered
suitable for semiconductors (Tramontano et al., 2020). Surface
functionalization as well provides a unique opportunity for sustained
and controlled drug release capacities and delivery potential.