Mineralization of Layer-by-Layer Ultrathin Films Containing Microfluidic-Produced Hydroxyapatite Nanorods

Abstract

We describe the assembly of layer-by-layer (LbL) ultrathin films containing bioactive hydroxyapatite (HAp) rod-shaped nanoparticles with mineralizing capacity. Monodisperse 96 nm long and nm wide HAp nanorods with a surface charge of-14 mV were produced with a microfluidic system. The negatively charged HAp nanorods were assembled with the polycation poly-L-lysine (PLL) in LbL fashion. The successful deposition of alternating layers was confirmed by quartz-crystal microbalance with dissipation monitoring. The Voigtbased viscoelastic model demonstrated steady film growth where three PLL/HAp bilayers reached a thickness of 70 nm. The bioactivity of [PLL/HAp] 3 was evaluated in vitro by following the formation of a mineralized hydroxyapatite layer in simulated body fluid (SBF). X-ray diffraction, energy-dispersive X-ray spectroscopy and scanning electron microscopy (SEM) demonstrated formation of a crystalline hydroxyapatite layer and complete surface coverage within 7 days. SaOs-2 osteoblasts-like cells attached to the mineralized surfaces and developed longer filopodia extensions when compared to non-mineralized samples. Our results showed that [PLL/HAp] 3 films are feasible osteoconductive coatings applicable to orthopedic implants and fixation devices.

Chondroitin Sulfate-Tyramine-Based Hydrogels for Cartilage Tissue Repair

“…In addition, among the various types of hydrogels, injectable hydrogels have also demonstrated great potential, as three-dimensional systems in cartilage tissue engineering, due to their framework mimicking cartilage lacuna, possessing a good penetration of nutrition and cell survival, having minimal invasive properties during injection into the articular joint, and having the ability to match irregular cartilage defects [ 40 ]. Besides enzymatic polymerization, the next generation of biomatrices based on layer-by-layer (LbL) ultrathin films [ 41 ], bioinks with nanoparticles [ 42 ] or magnetically-assisted 3D bioprinting constructs [ 43 ] are also of interest as future potential cartilage regeneration strategies.…”

Advanced Materials Based on Nanosized Hydroxyapatite

“…Its main advantage is the possibility for the incorporation of several classes of materials, including biomolecules and inorganic particles. In this sense, LbL allows the modulation of the distribution of different composites for applications such as biomaterial interfaces for implantable systems intended for bone regeneration [ 119 , 120 ].…”

Microfluidic encapsulation for controlled release and its potential for nanofertilisers

“…Figure 36a illustrates a microfluidic system composed of two associated Y-junction chips designed for the synthesis of HAp nanorods. 297,298 The morphology of HAp was controlled by the addition of surfactants (CTAB) as the micelles were converted from spherical into rod-like shape when the surfactant concentration surpassed the critical micellar concentration. The obtained HAp nanorods corresponding to the CTAB micelles with a narrow size distribution were confirmed by TEM analysis (Figure 36b).…”

“…(d) TEM images of dried hydroxyapatite powder (with kind permission of IOP science 295 )In general, different designs of microfluidic systems can be used to create particles with different shapes. Figure36aillustrates a microfluidic system composed of two associated Y-junction chips designed for the synthesis of HAp nanorods 297,298. The morphology of HAp was controlled by the addition of surfactants (CTAB) as the micelles were converted from spherical into rod-like shape when the surfactant concentration surpassed the critical micellar concentration.…”