**2.4 Functional bio-composites for medical application**

The bio-composites nowadays emanate with superior biocompatibility which perform in contemporaneous manner with the body. The architecture of these biocomposite materials is designed in such a manner that some exceptional characteristics are evolved eventually.

A combination of hydroxy apatite (HA) layer with high-density polyethylene (HDPE) as a substitution material for bone has been designed and commercialized as HAPEXTM [64–70]. In these cases, the span of HA was selected between 20 to 40 volume%. Recently, bone graft consisted of demineralized bone powder between two collagen layers was fostered and exhibited cell migration both in Vitro and in vivo investigation [71]. In another development, hydroxyapatite and a PEG/ PBT (polyethylene glycol and poly-butylene terephthalate) block copolymer composites were designed with enhanced chemical linkages by using hexamethylene diisocyanate as a coupling agent. They showed that the HA particles in conjunction with polymeric matrix with covalent bonding helps in achieving bone replacement [72].

A complicated bilayer coating of graphene oxide (GO) and Poly (ε-caprolactone) (PCL)/Gelatin-forsterite nanofibers on 316 L stainless steel (SS) were developed and ultimately it showed increased suitability as orthopedic implant with improved corrosion resistance of SS [73]. However, toxicity of metallic materials is still remained as a major concern for health safety. In this connection, the biocompatibility of the scaffolds was enhanced by designing new nanocomposite system with the activation of functionalized multi-walled carbon nanotubes, kappa-carrageenan, and chitosan in hydroxyapatite (MHAp) [74].

The pursuit for targeted and coordinated drug release achieved a new dimension with the manipulation of composite structure. Nanocomposites of N-isopropyl acrylamide (NIPAAm) hydrogel with magnetic nano iron oxide particles was formulated for the pulsatile drug delivery system. By alternating the high frequency magnetic field, the heat generation in nanocomposites was controlled to regulate the swelling transition of the hydrogel [75, 76]. For another instance, nanocomposites of paclitaxel were organized using poly- (D,L-lactide-co-glycolide)/montmorillonite (PLGA/MMT) nanoparticles decorated by human epidermal growth factor receptor-2 (HER2) antibody were designed for targeted chemotherapy treatment. The NP formulation exhibited a biphasic drug release with a moderate initial burst followed by a sustained release profile. The surface decoration speeded the drug release. PLGA-MMT demonstrated increased cellular uptake by CaCo-2 and HT-29 cells [77].

With the development of biocomposite technology, there are various types of dressings for different wounds were studied for better wound healing. Consequently, many therapeutic dressings with different architecture with diverse activity have materialized and employed medically, such as natural dressings, synthetic dressings, medical dressings, and tissue engineering dressing. A promising bio-nanocomposite from nanocellulose (NC), poly(vinyl pyrrolidone) (PVP), and chitosan was fabricated by solution casting method for in vitro wound dressings [78]. The solution blended PVP and chitosan mixer formed a biocompatible combination with nanocellulose particles via hydrogen bonding. The nanocomposite showed enhanced swelling, blood compatibility and antibacterial activity. Recently, Kamel's group have fabricated distinctive biocomposite membranes from banana

peel nano powder (BPnP) reinforcement in chitosan matrix. In this structure, glycerol was added as plasticizer and crosslinker to the membranes. It was found that the swelling properties of chitosan were reduced with the incorporation of BPnP. Furthermore, the results also showed that chitosan/BPnP membranes have a collaborative action with the highest activity at 10 wt% of BPnP loading [79].
