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Objective The first-order absorption is a common model used in Pharmacokinetics. The absorption of some drugs follows carrier mediated transport. It has been proposed that the amount of drug available may saturate the transport mechanism resulting in an absorption slower than the one predicted by the first-order model. Saturable absorption has been modeled at the differential equation level by substituting the constant rate absorption by a Hill kinetics absorption. However, its exact solution is so far unknown. The goal of this is to know the exact solution of different Hill kinetic absorption models. Methods We start defining different absorption models and increasing then their complexity. The simplest case is the first-order absorption model and the most complex will be a generalized Hill kinetic absorption model. The differential equation of each model is integrated. Results The complexity of the models their solutions may be not expressed in a close-form, or in term of elementary functions. We obtain and discuss the exact solutions of the different Hill kinetics absorption models. To do that, the solutions are studied according to the possible values of the free parameters of the models. We show the differences between models through simulations. Conclusions The knowledge of closed-form solutions allows to illustrate the differences between the different absorption models and minimizes the errors of numerical integration.

Polymer scaffolds are playing an increasing role in tissue engineering (TE), although there is still a need to improve their biomimicry of cellular microenvironments, by having smart scaffolds with an active response, which can improve tissue regeneration. This work reports on the novel combination of poly(lactic-co-glycolide) (PLGA) with the ionic liquid (IL) choline bis(trifluoromethylsulfonyl)imide ([Chol][TFSI]) or with iron oxide nanoparticles (Fe3O4, NP) in order to achieve biodegradable scaffolds with electroactive and magnetoactive response, respectively. The composites were processed into fiber and film morphologies. PLGA + IL fibers present diameters between 1.92 and 3.26 µm, decreased mechanical stiffness and elongation at yield with respect to the pristine polymer, and some fiber concentrations are not biocompatible. PLGA + IL films present a mean roughness 6.58 nm, increased mechanical stiffness with respect to the pristine polymer and decreased elongation at yield. The inclusion of IL increased the electrical conductivity of the polymer by 4 orders or magnitude.The diameter of PLGA + Fe3O4 fibers ranged from 0.62 to 1.36 µm, show an effective magnetic NP content yield between 52 and 78%, decreased stiffness and increased elongation at yield. PLGA + Fe3O4 films show a mean roughness of 5.07 nm, effective NP content yield between 77 and 97%, increased stiffness and elongation at yield. Cytotoxicity assays indicate that the PLGA + Fe3O4 materials are suitable for biomedical applications, independently of the filler content and morphology, whereas the IL containing samples are non-cytotoxic only in film morphology up to 5% wt. IL content. Finally, it is demonstrated that dynamic magneto mechanical stimulation of the PLGA + Fe3O4 samples allows the acceleration of the degradation rate of the samples., This work was supported by the Spanish State Research Agency (AEI) and the European Regional Development Fund (ERFD) through the project PID2019-106099RB-C43/AEI/10.13039/501100011033. Financial support from the Basque Government Industry departments under the ELKARTEK program is also acknowledged. The authors acknowledge funding by the Fundação para a Ciência e Tecnologia (FCT) and by ERDF through COMPETE2020 - Programa Operacional Competitividade e Internacionalização (POCI) in the framework of the Strategic Programs UID/FIS/04650/2020 and project PTDC/BTM MAT/28237/2017. Also, the authors thank FCT for the research grant SFRH/BPD/121526/2016 (DMC), SFRH/BD/148655/2019 (RMM) and 2021.08158.BD (JPS), and CR thanks the FCT for the contract under the Stimulus of Scientific Employment (2020.04163.CEECIND).

The nanoscale interface between hydroxyapatite (HA) particles and PLLA matrix appears to be the determining factor for poor mechanical performance of this family of biocomposites in load-bearing applications. It has been demonstrated that when these biocomposites are loaded, the physical adsorption between inorganic particles and polymeric matrix does not allow for load transfer and additional free surfaces that act as crack nucleators are created. To overcome this limitation, we propose plasma polymerization of poly (acrylic acid) (PAA) on HA particles as an effective method to produce strong interactions with the polylactide (PLLA) matrix. In this work, evidences of an intimate bonding between HAPAA particles and PLLA are given. Based on the thermodegradation behaviour of the composites it was found that the plasma deposited layer arrested free hydroxyl groups of PLLA chains, hindering the transesterification reactions that cause the thermal degradation of PLLA. As a result, thermal degradation of the composites was retarded and followed the chain scission route producing acetaldehyde, CO and CO2. From the mechanical characterization it became clear that load transfer was developed by means of the PAA compatibilized interface resulting in the observed enhancement of the elasticity and damping behaviour of the biocomposites.

A microemulsion method has been used for the synthesis of iron oxide nanoparticles and its aqueous stabilization. Iron oxide nanoparticles of 9±2 nm in size were then coated with gold in a second step. For this purpose HAuCl 4 was reduced employing glucose as a reducing agent. The mild conditions promote the reduction of Au ions adsorbed onto the γ-Fe 2 O 3 particles in order to ensure a controlled shell growth of gold, and avoiding the formation of new gold nuclei. Different molar ratios of HAuCl 4 /glucose were investigated. The obtained core–shell structures have been characterized by TEM, UV spectroscopy, XRD and Magnetometry measurements.