The gold standard material for bone regeneration is still autologous bone, a mesenchymal tissue that consists mainly of extracellular matrix (ECM) (90% v/v) and little cellular content (10% v/v). However, the fact that decellularized allogenic bone grafts often present a clinical performance comparable to autologous bone grafts demonstrates the crucial role of ECM in bone regeneration. For long, the mechanism by which bone allografts function was not clear, but recent research has unveiled many unique characteristics of ECM that seem to play a key role in tissue regeneration. This is further confirmed by the fact that synthetic biomaterials with composition and properties resembling bone ECM present excellent bone regeneration properties. In this context, ECM molecules such as glycosaminoglycans (GAGs) and self-assembly peptides (SAPs) can improve the performance of bone regeneration biomaterials. Moreover, decellularized ECM derived either from native tissues such as bone, cartilage, skin, and tooth germs or from cells such as osteoblasts, chondrocytes, and stem cells has shown promising results in bone regeneration applications. Understanding the role of ECM in bone regeneration is crucial for the development of the next generation of biomaterials for bone tissue engineering. In this sense, this review addresses the state-of-the-art on this subject matter.

The development of a reproducible procedure for the fabrication of Pt disk-shaped microelectrodes with characteristic dimensions ranging from 50 nm to 1 μm in diameter was carried out using a laser pulling technique. The governing physical phenomena involved in their fabrication are discussed, and the importance of adding a critical quartz thinning step in the general procedure is demonstrated. The preparation of the microelectrodes involves sealing a platinum wire inside a quartz tubing using a pipet puller, thinning the composite material (platinum/quartz assembly), and laser pulling it to obtain two microelectrodes. The resulting microelectrodes display reproducible well-controlled geometry, which is important to downstream quantitative scanning electrochemical studies and imaging. Mechanical polishing of the microelectrode is required and remains the critical step in the fabrication of nanometer size electrodes. Following production, the microelectrodes are characterized by electron microscopy, scanning electrochemical microscopy, and cyclic voltammetry. Development of these microelectrodes is motivated by their subsequent application to electrocatalysis and their potential in theoretical study because of their well-defined geometry.

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A molecular necklace of polypseudorotaxanes was prepared by threading β-cyclodextrins (β-CD) onto biodegradable and thermoresponsive polyurethanes derived from bile acids. These polyurethanes were synthesized via a simple step condensation of bile acid-based dicarbonate with poly(ethylene glycol)-diamine. The β-CD rings slide onto the poly(ethylene glycol) segments and selectively recognize the bile acid units of the polyurethane chains, whereas the poly(ethylene glycol) segments remain crystalline with a lower crystallinity. This bio-compound-derived molecular necklace can be visualized by scanning tunneling microscopy. The polypseudorotaxanes show thermosensitivity in water and the phase transition temperature may be fine-tuned by varying the molar ratios of β-CD to the bile acid units. Such an interesting necklace model of polypseudorotaxane constructed from natural compounds may lead to the further exploration of their applications, such as as an enzyme model, due to their biological nature.

Lamellar patterns resulting from the adsorption of p-dialkoxybenzene derivatives on HOPG have been investigated as molecular templates for directing the assembly of thiol-capped gold nanoparticles (AuNP). STM characterization at the liquid-solid interface reveals the periodic arrangement of AuNP on top of the self-assembled molecular network (SAMN), spanning hundreds of nanometers. The resulting superlattices are notably different from the close-packed structures formed by spherical nanoparticles during evaporative drying. The templating effect is based on van der Waals interactions of the alkyl chains of the SAMN and AuNP, and the assembly efficiency is greatest when these chains are of similar length.

Porphyrin molecules were immobilized on polycrystalline gold and glassy carbon by coordinating cobalt(II) 5,10,15,20-tetraphenyl-21H,23H-porphine to a 4-aminothiophenol self-assembled monolayer. The resulting electrocatalytic activity of the metalloporphyrin-modified substrates with regard to the oxygen reduction reaction was characterized by means of cyclic voltammetry and scanning electrochemical microscopy (SECM) using nanoelectrodes of well-defined geometry. From substrate generation tip collection (SG-TC) mode SECM measurements performed under steady-state conditions and at different applied substrate potentials, it is possible to extract kinetic information relevant to electrocatalyst substrates such as metalloporphyrin-modified gold and glassy-carbon electrodes. Such an approach allows for the isolation of the unique contribution of the electrocatalyst to the oxygen reduction reaction and peroxide formation.

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