Simulated Performance of a Xenohybrid Bone Graft (SmartBone®) in the Treatment of Acetabular Prosthetic Reconstruction.

Total hip arthroplasty (THA) is a surgical procedure for the replacement of hip joints with artificial prostheses. Several approaches are currently employed in the treatment of this kind of defect. Overall, the most common method involves using a quite invasive metallic support (a Burch-Schneider ring). Moreover, valid alternatives and less invasive techniques still need to be supported by novel material development. In this work, we evaluated the performance of SmartBone®, a xenohybrid bone graft composed of a bovine bone matrix reinforced with biodegradable polymers and collagen, as an effective support in acetabular prosthesis reconstruction. Specifically, the material's mechanical properties were experimentally determined (E = ~1.25 GPa, Ef = ~0.34 GPa, and Et = ~0.49 GPa) and used for simulation of the hip joint system with a SmartBone® insert. Moreover, a comparison with a similar case treated with a Burch-Schneider ring was also conducted. It was found that it is possible to perform THA revision surgeries without the insertion of an invasive metal support and it can be nicely combined with SmartBone®'s osteointegration characteristics. The material can withstand the loads independently (σmax = ~12 MPa) or be supported by a thinner titanium plate in contact with the bone in the worst cases. This way, improved bone regeneration can be achieved.

Mechanical phase inversion of Pickering emulsions via metastable wetting of rough colloids.

The possibility to invert emulsions from oil-in-water to water-in-oil (or vice versa) in a closed system, i.e. without any formulation change, remains an open fundamental challenge with many opportunities for industrial applications. Here, we propose a mechanism that exploits particle surface roughness to induce metastable wetting and obtain mechanically-responsive Pickering emulsions. We postulate that the phase inversion is driven by an in situ switch of the particle wettability from metastable positions at the interface following the input of controlled mechanical energy. Oil-in-water emulsions can be prepared at low energy using mildly hydrophobic rough colloids, which are dispersed in water and weakly pinned at the interface, and switched to water-in-oil emulsions by a second emulsification at higher energy, which triggers the relaxation of the particle contact angle. The same principle is demonstrated for the complementary emulsions using mildly hydrophilic colloids initially dispersed in oil. Our experiments and simulations support that the delicate interplay between particle surface design during synthesis and the energy of the emulsification process can encode a kinetic pathway for the phase inversion. Both organic and inorganic nanoparticles can be used, allowing for the future implementation of our strategy in a broad range of smart industrial formulations.

Synthesis of metal-doped nanoplastics and their utility to investigate fate and behaviour in complex environmental systems.

Research on the distribution and effects of particulate plastic has intensified in recent years and yet, due to analytical challenges, our understanding of nanoplastic occurrence and behaviour has remained comparatively elusive. However, process studies could greatly aid in defining key parameters for nanoplastic interactions within and transfers between technical and environmental compartments. Here we provide a method to synthesize nanoplastic particles doped with a chemically entrapped metal used as a tracer, which provides a robust way to detect nanoplastics more easily, accurately and quantitatively in complex media. We show the utility of this approach in batch studies that simulate the activated sludge process of a municipal waste water treatment plant and so better understand the fate of nanoplastics in urban environments. We found that the majority of particles were associated with the sludge (>98%), with an average recovery of over 93% of the spiked material achieved. We believe that this approach can be developed further to study the fate, transport, mechanistic behaviour and biological uptake of nanoplastics in a variety of systems on different scales.

Improving Bovine Bone Mechanical Characteristics for the Development of Xenohybrid Bone Grafts.

BACKGROUND: The further functionalization of natural existing biomaterials is a very efficient method to introduce additional advanced characteristics on a unique structural composition and architecture. OBJECTIVE: As an example, different animal sources, if properly treated, can be used to develop bone xenograft active in hard tissues regeneration. In this sense, it is also important to consider that the selected process has to take into consideration the intrinsic variability of the base material itself and possibly being able to compensate for it. METHODS: In this work we characterize cancellous bovine bone treated by deposition of polymer and collagen and we show that the added components not only lead to a more resistant and more hydrophilic material, but also reduce the conventional correlation between apparent density and elastic modulus, which, in general, is a major source of uncertainty and risk in xenografts usage. RESULTS: Moreover, though intrinsically reinforcing the material, the deposition process leaves the specific open-porous structure, that allows cells proliferation and vessels ingrowth, basically unaltered. CONCLUSION: The final material combines in a single piece and at the same time, mechanical resistance, homogeneous mechanical response and proper structural characteristics that allow further integration within the patient autochthonous tissues.

Preparation of perfusive chromatographic materials via shear-induced reactive gelation.

A simple method for producing highly porous materials suitable for chromatographic applications is discussed. Starting from a dispersion of polymer core-shell nanoparticles (latex), micrometer sized clusters (100 µm) are produced via shear-induced Reactive Gelation. Thanks to their fractal structure, these aggregates exhibit highly porous structures, with pore size distribution ranging from 0.1 to several micrometers. The effect of different properties of the primary nanoparticles on the qualities of the final products is also investigated. Particle architecture, namely the ratio between the hard, highly crosslinked core, and the soft, poorly crosslinked shell, turned out to be the most important parameter to be tuned in order to obtain highly porous and mechanically resistant clusters. The final materials can be easily slurry-packed into conventional chromatographic columns. In comparison to other commercial stationary phases, these materials show not only much lower pressure drops at very high flow rates (i.e. <0.2 bar/cm at 6 mL/min), but also HETP profiles independent of fluid velocity when measured with tracers of sizes comparable to typical bio-macromolecules. Moreover, these materials, while offering the key advantage of being in a slurry form and thus easily packable and scalable, have a behavior that closely resembles that of monoliths, in which convective flow contribution dominates.

A Methodologic Approach for the Selection of Bio-Resorbable Polymers in the Development of Medical Devices: The Case of Poly(l-lactide-co-ε-caprolactone).

In the last decades bioresorbable and biodegradable polymers have gained a very good reputation both in research and in industry thanks to their unique characteristics. They are able to ensure high performance and biocompatibility, at the same time avoiding post-healing surgical interventions for device removal. In the medical device industry, it is widely known that product formulation and manufacturing need to follow specific procedures in order to ensure both the proper mechanical properties and desired degradation profile. Moreover, the sterilization method is crucial and its impact on physical properties is generally underestimated. In this work we focused our attention on the effect of different terminal sterilization methods on two commercially available poly(l-lactide-co-ε-caprolactone) with equivalent chemical composition (70% PLA and 30% PCL) and relatively similar initial molecular weights, but different chain arrangements and crystallinity. Results obtained show that crystallinity plays a key role in helping preserve the narrow distribution of chains and, as a consequence, defined physical properties. These statements can be used as guidelines for a better choice of the most adequate biodegradable polymers in the production of resorbable medical devices.

Tracking of Fluorescently Labeled Polymer Particles Reveals Surface Effects during Shear-Controlled Aggregation.

Surface chemistry is believed to be the key parameter affecting the aggregation and breakage of colloidal suspensions when subjected to shear. To date, only a few works dealt with the understanding of the role of the physical and chemical properties of the particles' surface upon aggregation under shear. Previous studies suggested that surface modifications strongly affect polymer particles' adhesion, but it was very challenging to demonstrate this effect and monitor these alterations upon prolonged exposure to shear forces. More importantly, the mechanisms leading to these changes remain elusive. In this work, shear-induced aggregation experiments of polymer colloidal particles have been devised with the specific objective of highlighting material transfer and clarifying the role of the softness of the particle's surface. To achieve this goal, polymer particles with a core-shell structure comprising fluorescent groups have been prepared so that the surface's softness could be tuned by the addition of monomer acting as a plasticizer and the percentage of fluorescent particles could be recorded over time via confocal microscopy to detect eventual material transfer among different particles. For the first time, material exchange occurring on the soft surface of core-shell polymer microparticles upon aggregation under shear was observed and proved. More aptly, starting from a 50% labeled/nonlabeled mixture, an increase in the percentage of particles showing a fluorescent signature was recorded over time, reaching a fraction of 70% after 5 h.