Fine Tuning of the Mechanical Properties of Bio-Based PHB/Nanofibrillated Cellulose Biocomposites to Prevent Implant Failure Due to the Bone/Implant Stress Shielding Effect.

A significant mechanical properties mismatch between natural bone and the material forming the orthopedic implant device can lead to its failure due to the inhomogeneous loads distribution, resulting in less dense and more fragile bone tissue (known as the stress shielding effect). The addition of nanofibrillated cellulose (NFC) to biocompatible and bioresorbable poly(3-hydroxybutyrate) (PHB) is proposed in order to tailor the PHB mechanical properties to different bone types. Specifically, the proposed approach offers an effective strategy to develop a supporting material, suitable for bone tissue regeneration, where stiffness, mechanical strength, hardness, and impact resistance can be tuned. The desired homogeneous blend formation and fine-tuning of PHB mechanical properties have been achieved thanks to the specific design and synthesis of a PHB/PEG diblock copolymer that is able to compatibilize the two compounds. Moreover, the typical high hydrophobicity of PHB is significantly reduced when NFC is added in presence of the developed diblock copolymer, thus creating a potential cue for supporting bone tissue growth. Hence, the presented outcomes contribute to the medical community development by translating the research results into clinical practice for designing bio-based materials for prosthetic devices.

Starch-based orodispersible film for diclofenac release

Abstract The form of drug administration affects the success of treatment, since it can influence adherence of the patient to the therapy. The use of orodispersible films has emerged as a way to overcome some drawbacks of conventional methods of drug delivery, especially for patients experiencing difficulty in swallowing. These films are prepared using a matrix that incorporates the drug and contains other substances that confer the properties of the system. The present work describes the use of thermoplastic starch as a carrier for the model drug diclofenac, including film preparation and testing of its orodispersible potential. Preparation of the film employed a microwave oven to gelatinize and plasticize corn starch, with incorporation of the model drug, followed by solvent-casting. The samples were characterized using mechanical tests, analyses of water uptake and water content, and Fourier transform infrared spectroscopy. The results indicated that the film presented promising properties as an alternative system for oral drug administration, with good incorporation and distribution of the drug in the matrix. The material displayed satisfactory mechanical properties, which are crucial for this type of material, due to the need for oral administration and handling before use.

Biodegradable scaffolds based on plant stems for application in regenerative medicine.

Several synthetic and natural materials have been studied for the confection of temporary grafts for application in regenerative medicine, however, the development of a material with adequate properties remains a challenge, mainly because its degradation kinetics in biological systems. Nature provides materials with noble properties that can be used as such for many applications, thus, taking advantage of the available morphology and assembled structures of plants, we propose to study the vegetable stems for use as temporary graft. Since thein vivodegradation is maybe one of the most important features of the temporary grafts, here we have implanted the plant stems from pumpkin, papaya, and castor into the subepithelial tissue of animals and followed their biodegradation process and the local inflammatory response. Mechanical tests, FTIR and contact angle with water were also analysed. The results indicated the mechanical properties and the contact angle were adequate for use in regenerative medicine. The results of thein vivostudies indicated a beneficial inflammatory process and a gradual disintegration of the materials within 60 days, suggesting the plants stems as new and potential materials for development of grafts for use in the field of regenerative medicine.

Bioactive Fibrin Scaffolds for Use in Musculoskeletal Regenerative Medicine

Abstract Autologous fibrin matrices derived from the Leukocyte and Platelet Rich Plasma (L-PRP) and Leukocyte and Platelet Rich Fibrin (L-PRF) techniques present great potential to act as a bioactive scaffold in regenerative medicine, contributing to the maintenance of cell viability, proliferation stimulus and differentiation. In contrast, there are few studies that characterize the bioactive potential of these fibrin scaffolds by considering the process of production. The objective of this work was to characterize the intrinsic potential of maintaining cell viability of different fibrin scaffolds containing platelets and leukocytes. In order to achieve that, blood samples from a volunteer were collected and processed to obtain fibrin clots using the suggested techniques. To characterize the potential for in vitro viability, mesenchymal stem cells from human infrapatellar fat were used. The scaffolds were cellularized (1x105 cells/scaffolds) and maintained for 5 and 10 days under culture conditions with Dulbecco's Modified Eagle Medium, without addition of fetal bovine serum, and subsequently subjected to analyses by Fourrier transform infra-red spectroscopy, circular dichroism and fluorescence microscopy. The results demonstrated distinct intrinsic potential viability between the scaffolds, and L-PRP was responsible for promoting higher levels of viability in both periods of analysis. No viable cells were identified in the fibrin matrix used as controls. These results allow us to conclude that both fibrin substrates have presented intrinsic potential for maintaining cell viability, with superior potential exhibited by L-PRP scaffold, and represent promising alternatives for use as bioactive supports in musculoskeletal regenerative medicine.

Thermally reversible nanocellulose hydrogels synthesized via the furan/maleimide Diels-Alder click reaction in water.

The study deals with the synthesis of thermally reversible hydrogels from modified cellulose nanofibers via the Diels-Alder "click" reaction in an aqueous medium. "Never-dried" cellulose fibres derived from hardwood were submitted to shearing and surface TEMPO-oxidation before being modified with furfurylamine. The ensuing pendant furan moieties were reacted with a water-soluble bismaleimide via Diels-Alder coupling at 65 °C to produce a hydrogel, whose deconstruction was induced by the corresponding retro-Diels-Alder reaction carried out at 95 °C. Differential scanning calorimetry and rheological measurement were used to characterize the hydrogels. These aqueous cellulosic materials should provide original applications in such areas as strong paper-based artefacts and biocompatible gels.

Sleeving nanocelluloses by admicellar polymerization.

This investigation reports the first application of admicellar polymerization to cellulose nanofibers in the form of bacterial cellulose, microfibrillated cellulose, and cellulose nanowhiskers using styrene and ethyl acrylate. The success of this physical sleeving was assessed by SEM, FTIR, and contact angle measurements, providing an original and simple approach to the modification of cellulose nanofibers in their pristine aqueous environment.