Biofunctionalization strategies on tantalum-based materials for osseointegrative applications

The use of tantalum as biomaterial for orthopedic applications is gaining considerable attention in the clinical practice because it presents an excellent chemical stability, body fluid resistance, biocompatibility, and it is more osteoconductive than titanium or cobalt-chromium alloys. Nonetheless, metallic biomaterials are commonly bioinert and may not provide fast and long-lasting interactions with surrounding tissues. The use of short cell adhesive peptides derived from the extracellular matrix has shown to improve cell adhesion and accelerate the implant’s biointegration in vivo. However, this strategy has been rarely applied to tantalum materials. In this work, we have studied two immobilization strategies (physical adsorption and covalent binding via silanization) to functionalize tantalum surfaces with a cell adhesive RGD peptide. Surfaces were used untreated or activated with either HNO3 or UV/ozone treatments. The process of biofunctionalization was characterized by means of physicochemical and biological methods. Physisorption of the RGD peptide on control and HNO3-treated tantalum surfaces significantly enhanced the attachment and spreading of osteoblast-like cells; however, no effect on cell adhesion was observed in ozone-treated samples. This effect was attributed to the inefficient binding of the peptide on these highly hydrophilic surfaces, as evidenced by contact angle measurements and X-ray photoelectron spectroscopy. In contrast, activation of tantalum with UV/ozone proved to be the most efficient method to support silanization and subsequent peptide attachment, displaying the highest values of cell adhesion. This study demonstrates that both physical adsorption and silanization are feasible methods to immobilize peptides onto tantalum-based materials, providing them with superior bioactivity.Peer Reviewe

Pediatric HIV care cascade in southern mozambique: Missed opportunities for early ART and re-engagement in care

© 2020 Wolters Kluwer Health, Inc. All rights reserved. Background: There are 170,000 children living with HIV in 2017 in Mozambique. Scaling-up HIV care requires effective retention along the cascade. We sought to evaluate the pediatric cascade in HIV care at the Manhiça District Hospital. Methods: A prospective cohort of children <15 years was followed from enrollment in HIV care (January 2013 to December 2015) until December 2016. Loss to follow-up (LTFU) was defined as not attending the HIV hospital visits for ≥90 days following last visit attended. Results: From the 438 children included {median age at enrollment in care of 3,6 [interquartile range (IQR): 1.1-8.6] years}, 335 (76%) were antiretroviral therapy (ART) eligible and among those, 263 (78%) started ART at enrollment in HIV care. A total of 362 children initiated ART during the study period and the incidence rate of LTFU at 12, 24, and 36 months post-ART initiation was 41 [95% confidence interval (CI): 34-50], 34 (95% CI: 29-41), and 31 (95% CI: 27-37) per 100 children-years, respectively. Median time to LTFU was 5.8 (IQR: 1.4-12.7) months. Children 5-9 years of age had a lower risk of LTFU compared with children <1 year [adjusted subhazard ratio 0.36 (95% CI: 0.20-0.61)]. Re-engagement in care (RIC) was observed in 25% of the LTFU children. Conclusions: The high LTFU found in this study highlights the special attention that should be given to younger children during the first 6 months post-ART initiation to prevent LTFU. Once LTFU, only a quarter of those children return to the health unit. Elucidating factors associated with RIC could help to fine tune interventions which promote RIC

Single-step pulsed electrodeposition of calcium phosphate coatings on titanium for drug delivery

Metallic implants have some limitations related to bioactivity and bacteria colonization leading to infections. In this regard, calcium phosphate coatings can be used as carrier for drug delivery in order to improve the mentioned drawbacks. The present work proposes the introduction of an antibacterial agent in the course of a pulsed and reverse pulsed electrodeposition. Calcium phosphate coatings were prepared in 30min using different pulse waveforms (unipolar-bipolar), current densities (2–5mA/cm2) and temperatures (40–60°C). Mechanical stability of the as-coated surfaces was studied in order to select the optimal electrodeposition conditions. Subsequently, selected coatings were loaded with an antiseptic agent, chlorhexidine digluconate (CHX), via a single-step co-deposition procedure. CHX concentration added to the electrolyte was adjusted to 3mM based on the antibacterial efficacy of the loaded coatings evaluated in vitro with Staphylococcus aureus and Escherichia coli bacteria strains. Whereasthe same chlorhexidineconcentration was addedto the electrolyte, results showedthat the amount of CHX loaded was different for each condition while release kinetics was maintained. The results of this work demonstrate that a pulsed co-deposition strategy has great potential to modulate local delivery of antibacterial agents such as chlorhexidine digluconate, which may prevent early phase infections of metallic implants after insertion

Discordant retention of HIV-infected mothers and children

It is often assumed that children and their caregivers either stay in care together or discontinue together, but data is lacking on caregiver-child retention concordance. We sought to describe the pattern of care among a cohort of human immunodeficiency virus (HIV) infected children and mothers enrolled in care at the Manhiça District Hospital (MDH).This was a retrospective review of routine HIV clinical data collected under a larger prospective HIV cohort study at MDH. Children enrolling HIV care from January 2013 to November 2016 were identified and matched to their mother's HIV clinical data. Retention in care for mothers and children was assessed at 24 months after the child's enrolment. Multinomial logistic regression was performed to evaluate variables associated with retention discordance.For the 351 mother-child pairs included in the study, only 39% of mothers had concordant care status at baseline (23% already active in care, 16% initiated care concurrently with their children). At 24-months follow up, a total of 108 (31%) mother-child pairs were concordantly retained in care, 88 (26%) pairs were concordantly lost to follow up (LTFU), and 149 (43%) had discordant retention. Pairs with concurrent registration had a higher probability of being concordantly retained in care. Children who presented with advanced clinical or immunological stage had increased probability of being concordantly LTFU.High rates of LTFU as well as high proportions of discordant retention among mother-child pairs were found. Prioritization of a family-based care model that has the potential to improve retention for children and caregivers is recommended

Mineralization of Titanium Surfaces: Biomimetic Implants

The surface modification by the formation of apatitic compounds, such as hydroxyapatite, improves biological fixation implants at an early stage after implantation. The structure, which is identical to mineral content of human bone, has the potential to be osteoinductive and/or osteoconductive materials. These calcium phosphates provoke the action of the cell signals that interact with the surface after implantation in order to quickly regenerate bone in contact with dental implants with mineral coating. A new generation of calcium phosphate coatings applied on the titanium surfaces of dental implants using laser, plasma-sprayed, laser-ablation, or electrochemical deposition processes produces that response. However, these modifications produce failures and bad responses in long-term behavior. Calcium phosphates films result in heterogeneous degradation due to the lack of crystallinity of the phosphates with a fast dissolution; conversely, the film presents cracks, which produce fractures in the coating. New thermochemical treatments have been developed to obtain biomimetic surfaces with calcium phosphate compounds that overcome the aforementioned problems. Among them, the chemical modification using biomineralization treatments has been extended to other materials, including composites, bioceramics, biopolymers, peptides, organic molecules, and other metallic materials, showing the potential for growing a calcium phosphate layer under biomimetic conditions

Mineralization of titanium surfaces: biomimetic implants

The surface modification by the formation of apatitic compounds, such as hydroxyapatite, improves biological fixation implants at an early stage after implantation. The structure, which is identical to mineral content of human bone, has the potential to be osteoinductive and/or osteoconductive materials. These calcium phosphates provoke the action of the cell signals that interact with the surface after implantation in order to quickly regenerate bone in contact with dental implants with mineral coating. A new generation of calcium phosphate coatings applied on the titanium surfaces of dental implants using laser, plasma-sprayed, laser-ablation, or electrochemical deposition processes produces that response. However, these modifications produce failures and bad responses in long-term behavior. Calcium phosphates films result in heterogeneous degradation due to the lack of crystallinity of the phosphates with a fast dissolution; conversely, the film presents cracks, which produce fractures in the coating. New thermochemical treatments have been developed to obtain biomimetic surfaces with calcium phosphate compounds that overcome the aforementioned problems. Among them, the chemical modification using biomineralization treatments has been extended to other materials, including composites, bioceramics, biopolymers, peptides, organic molecules, and other metallic materials, showing the potential for growing a calcium phosphate layer under biomimetic conditions.Ramón y Cajal Beca a C.M.-M. RYC-2015-18566Cofinanciados por la UE a través de la Unión Europea Fondos de Desarrollo Regional