BUSCADOR RECOLECTA

In the present work, a hybrid hierarchical coating (HHC) system comprising a plasma electrolytic oxidation (PEO) coating and a homogeneously porous structured polycaprolactone (PCL) top-coat layer, loaded with ciprofloxacin (CIP), was developed on Mg3Zn0.4Ca alloy. According to the findings, the HHC system avoided burst release and ensured gradual drug elution (64% over 240 h). The multi-level protection of the magnesium alloy is achieved through sealing of the PEO coating pores by the polymer layer and the inhibiting effect of CIP (up to 74%). The corrosion inhibition effect of HHC and the eluted drug is associated with the formation of insoluble CIP-Me (Mg/Ca) chelates that repair the defects in the HHC and impede the access of corrosive species as corroborated by FTIR spectra, EIS and SEM images after 24 h of immersion. Therefore, CIP participates in an active protection mechanism by interacting with cations coming through the damaged coating., The authors gratefully acknowledge the support of the ADITIMAT-CM (S2018/NMT-4411, the Regional Government of Madrid and EU Structural Funds), PID2021-124341OB-C22 and RTI2018-096328-B-I00 (MICINN/AEI/FEDER, UE) projects. Mr. Cheng Wang thanks the China Scholarship Council for the award of fellowship and funding No. 201806310128. Finally, we thank the PIT FAB3D, PTI + Salud Global, and the PTI + SUSPLAST from CSIC for their support., Peer reviewed

A hierarchical hybrid coating (HHC) comprising a ceramic oxide layer and two biodegradable polymeric (polycaprolactone, PCL) layers has been developed on Mg3Zn0.4Ca cast alloy in order to provide a controlled degradation rate and functionality by creating a favorable porous surface topography for cell adhesion. The inner, ceramic layer formed by plasma electrolytic oxidation (PEO) has been enriched in bioactive elements (Ca, P, Si). The intermediate PCL layer sealed the defect in the PEO layer and the outer microporous PCL layer loaded with the appropriate active molecule, thus providing drug-eluting capacity. Morphological, chemical, and biological characterizations of the manufactured coatings loaded with ciprofloxacin (CIP) and paracetamol (PAR) have been carried out. In vitro assays with cell lines relevant for cardiovascular implants and bone prosthesis (endothelial cells and premyoblasts) showed that the drug-loaded coating allows for cell proliferation and viability. The study of CIP and PAR cytotoxicity and release rate indicated that the porous PCL layer does not release concentrations detrimental to the cells. However, complete system assays revealed that corrosion behavior and increase of the pH negatively affects cell viability. H2 evolution during corrosion of Mg alloy substrate generates blisters in PCL layer that accelerate the corrosion locally in crevice microenvironment. A detailed mechanism of the system degradation is disclosed. The accelerated degradation of the developed system may present interest for its further adaptation to new cancer therapy strategies., This research was funded by MCIU/AEI/FEDER, UE, grant number PID2021-124341OB-C22; Regional Government of Madrid and EU Structural Funds, grant number S2018/NMT-4411, Peer reviewed

A hybrid hierarchical coating (HHC) biodegradable system, consisting of a ceramic (PEO) and a biodegradable microporous polymeric (PLA or PCL) layers, was developed on Mg3Zn0.4Ca alloy and evaluated under quasi-in vivo conditions. The polymer top-coat was produced using the Breath Figures approach by dip-coating the PEO treated ceramic surface onto a PLA/PCL polymer solution and withdraw under high relative humidity. According to our findings, when the polymer coating is applied directly onto the PEO layer using high humidity a negligible corrosion protection was observed. However, this issue was overcome by first applying a thin sealing polymer layer before the microporous polymer layer prepared by dip-coating in the absence of moisture. The HHC system improves the corrosion resistance by 10–12 times compared to the stand-alone PEO coating and, due to its inherent porosity, should be amenable for further functionalization with pharmaceutical agents., The authors gratefully acknowledge the support of PID2021-
124341OB-C22 (MCIU/AEI/FEDER, UE) and ADITIMAT-CM
(S2018/NMT-4411, Regional Government of Madrid and
EUStructural Funds). M. Mohedano is grateful for the support
of RYC-2017-21843 Ministerio de Ciencia e Innovación. Finally,
we thank the PTI FAB3D, PTIþSalud Gobal, and the
PTIþSUSPLAST from CSIC for their support.

Bioactive plasma electrolytic oxidation (PEO) coatings were developed on a wrought Mg0.5Zn0.2Ca alloy using a transparent electrolyte for easy maintenance and waste disposal, compared to a conventional suspension-based solution. Treatment times of 300, 600, and 900 s were evaluated for their effects on coating morphology, composition, and corrosion resistance. A short-time electrochemical impedance spectroscopy (EIS) screening was utilized to identify coatings with optimal corrosion protection. To assess the degradation rate and corrosion mechanisms, hydrogen evolution was monitored under pH-controlled quasi-in vivo conditions over extended immersion periods. Coating thickness increased by only 3% from 300 to 900 s of treatment (13 and 18 µm, respectively), with pore bands formed near the barrier layer at 900 s. The short-term EIS screening revealed that the coatings produced at 600 and 900 s were less protective and consistent than those at 300 s due to the presence of pore bands, which increased permeability. Hydrogen evolution measurements during 5 days of immersion at pH 7.4 indicated a tenfold higher degradation rate of the PEO-coated alloy compared to the bare substrate. Therefore, none of the PEO coatings provided effective corrosion protection after 24 h of immersion, which is attributed to crack formation at the PEO/corrosion products interface. This highlights the importance of crevices in the corrosion of Mg-Zn-Ca alloys. The presence of ZnO exacerbates the corrosion of magnesium in crevice areas., The support of the ADITIMAT-CM project (S2018/NMT-4411, Regional Government of Madrid and EU Structural and Social Funds) and PID2021-124341OB-C22 (MCIU) are
gratefully acknowledged. M. Mohedano is grateful for the support of RYC-2017-21843.

Cardiovascular disease caused by the accumulation of atheroma plaques in the coronary arteries and the subsequent decrease in the blood flow through the affected vessel, known as atherosclerosis, is responsible for a high percentage of deaths worldwide. Angioplasty is practiced to treat atherosclerosis which involves inserting a stent inside the occluded vessel to expand it and restore normal blood flow. In this work, temporary biodegradable stents made of AZ31 magnesium alloy have been fabricated using photo-chemical etching. The stents were coated via plasma electrolytic oxidation (PEO) technique. The radial strength of the stents was evaluated by cyclic compression, and the corrosion protection provided by the PEO coatings was studied by electrochemical and in vitro corrosion tests respectively. The stents showed an optimal maximum radial force of 0.147 N/mm and revealed elastic recuperation lower than 7 % of the total deformation after expansion. The applied PEO coating helped to control the corrosion of the magnesium alloy, delaying its initiation and, once it has started, decreased the degradation rate compared with the bare AZ31 samples. Thus, the stents treated with the PEO coatings developed in this research present promising results for their use as temporary medical devices used in angioplasty., The authors gratefully acknowledge the support of PID2021- 124341OB-C21 and PID2021-124341OB-C22 (MICINN/AEI/FEDER, UE) and ADITIMAT-CM (S2018/NMT-4411, Regional Government of Madrid and EU Structural Funds). The UC team would like to acknowledge the support by NSF through grant EEC-0812348., Peer reviewed

Corrosion fatigue is a major factor leading to sudden failures in load-bearing orthopaedic implants, particularly in biodegradable ones that corrode more quickly than permanent implants. In the current study, we developed a novel modified-in vitro corrosion fatigue (MICorF) rig that incorporates several key parameters—such as loading mode, blood buffering capacity, gradual bone healing processes, and the synchronization of corrosion and cyclic damage—aimed at closely mimicking in vivo conditions. The functionality of the MICorF was tested with an experimental extruded ZX00 (Mg-0.5Zn-0.5Ca) Mg alloy. The results showed that the ZX00 Mg alloy possesses a limited biomechanical performance. Based on the SEM micrographs, the presence of intermetallic particles in the alloy microstructure and the subsequent galvanic corrosion phenomena could be taken as the main cause of failure. According to the results yielded by the MICorF, the ZX00 alloy withstands at least 20 days under the studied physiological conditions and polarization corresponding to the pitting conditions., The authors gratefully acknowledge Larestan University of Medical Science and SADID Company (Dr Hojjatollah Rokhgireh) for their respectively financial (Grant No. 011-1397) and technical supports. This work was also supported by PID2021-124341OB-C22 (MICIU/AEI/10.13039/501100011033/FEDER, UE) and S2018/NMT-4411 (Regional government of Madrid and EU Structural and Social Funds). Marta Mohedano is grateful for the support of RYC-2017-21843. We highly appreciate Dr Jan Bohlen for supplying ZX00 Mg alloy.

To regulate the degradation rate and improve the surface biocompatibility of the AZ31B magnesium alloy, three different coating systems were produced via plasma electrolytic oxidation (PEO): simple PEO, PEO incorporating multi-walled carbon nanotubes (PEO + CNT), and a duplex coating that included a polycaprolactone top layer (PEO + CNT/PCL). Surfaces were characterized by chemical content, roughness, topography, and wettability. Biological properties analysis included cell metabolism and adhesion. PEO ± CNT resulted in an augmented surface roughness compared with the base material (BM), while PCL deposition produced the smoothest surface. All surfaces had a contact angle below 90°. The exposure of gFib-TERT and bmMSC to culture media collected after 3 or 24 h did not affect their metabolism. A decrease in metabolic activity of 9% and 14% for bmMSC and of 14% and 29% for gFib-TERT was observed after 3 and 7 days, respectively. All cells died after 7 days of exposure to BM and after 15 days of exposure to coated surfaces. Saos-2 and gFib-TERT adhered poorly to BM, in contrast to bmMSC. All cells on PEO anchored into the pores with filopodia, exhibited tiny adhesion protrusions on PEO + CNT, and presented a web-like spreading with lamellipodia on PEO + CNT/PCL. The smooth and homogenous surface of the duplex PEO + CNT/PCL coating decreased magnesium corrosion and led to better biological functionality.

The effects of multi-walled carbon nanotubes (MWCNTs) incorporation and polycaprolactone (PCL) post-treatment on the environmental-assisted cracking behaviour of a plasma electrolytic oxidation (PEO) coated AZ31B Mg alloy were elucidated in this study. Slow strain rate tensile (SSRT) experiments were carried out in simulated body fluid (SBF) for the bare material and different coating systems with and without MWCNTs and PCL overlay. Electrochemical impedance spectroscopy (EIS) and microscopic examinations (SEM and optical) were also conducted to reveal the role of corrosion on the mechanical response. In spite of the significant positive influence of the PEO coatings (with and without MWCNTs) on the bio-electrochemical behaviour of the AZ31B alloy, the environmental-assisted cracking performance was only marginally improved. Furthermore, PEO+MWCNTs/PCL coating system increased the fracture strain of the specimens by 7% compared to the uncoated specimens. Based on the SEM and optical micrographs, hydrogen embrittlement was suggested as the main cause of failure of the coated specimens under the in vitro slow strain rate test conditions.

In this study, a phosphate-based conversion coating (PCC) was applied as a precursor before forming silicate-fluoride (SiF) and silicate-phosphate-fluoride (SiPF) based flash-plasma electrolytic oxidation (Flash-PEO) coatings on AZ31B magnesium alloy. The main novelty is the successful incorporation of calcium, zinc, manganese and phosphate species into the Flash-PEO coatings via a precursor layer rather than using the electrolyte. The precursor also led to longer lasting and more intense discharges during the PEO process, resulting in increased pore size. Corrosion studies revealed similar short-term performance for all coatings, with impedance modulus at low frequencies above 107 Ωcm2, and slightly better performance for the SiPF-based coating. Nonetheless, the enlarged pores in the PEO coatings functionalized with the PCC precursor compromised the effectiveness of self-healing mechanisms by creating diffusion pathways for corrosive species, leading to earlier failure. These phenomena were effectively monitored by recording the open circuit potential during immersion in 0.5 wt.% NaCl solution. In summary, this study demonstrates that conversion coatings are a viable option for the functionalization of PEO coatings on magnesium alloys, as they allow for the incorporation of cationic and other species. However, it is crucial to maintain a small pore size to facilitate effective blockage through self-healing mechanisms.