We have developed plasmonic fibrin-based hydrogels that incorporate gold nanoparticles which transduce incident near-infrared (NIR) light into heat. Human adenovirus serotype type-5 vectors encoding a firefly luciferase (fLuc) coding sequence driven by a heat-inducible promoter were incorporated into the hydrogels. Transmission electronic microscopic analysis revealed that the adenoviral vectors were associated to the fibrin fibers. In vitro experiments in which human cells were cultured with plasmonic hydrogels showed that the adenoviral vectors can diffuse from the hydrogels, transduce the cells, and stimulate heat-induced transgene expression upon NIR irradiation. The hydrogels were implanted in 4.2 mm drill hole defects generated in the humerus of male rabbits. Three days after implantation, the defects were NIR-irradiated. Six h later, the animals were euthanized and samples from the bone defect zone were processed for immunohistochemical analyses using a specific fLuc antibody. The results showed strong expression of fLuc in tissues surrounding the implants of NIR-irradiated rabbits, while non- irradiated animals exhibited negligible expression. We next aimed to use the temperature increase to induce the production of transgenic bone morphogenetic protein 6 (BMP-6), using safe gene switches that can provide tighter control of in vivo transgene expression than heat-inducible promoters. These switches are only activated by heat in the presence of rapamycin and maintain a high level of targeted transgene expression for several days after heat activation. Adenoviral vectors encoding the safe switches that control the expression of BMP-6 were incorporated to the composites. The resulting NIR-responsive hydrogels were implanted in the bone defects generated in rabbits and used as a platform to transduce host cells, generate local hyperthermia and stimulate BMP-6 production.

Acknowledgements: This research was supported by grants RTI2018-095159-B-I00 and PID2021-126325OB-I00 (MCIN/AEI/10.13039/501100011033 and “ERDF A way of making Europe”), by grant P2022/BMD- 7406 (Regional Government of Madrid). M.A.L-J. is the recipient of predoctoral fellowship PRE2019-090430 (MCIN/AEI/10.13039/501100011033).

Objectives

To evaluate the in vitro effects of hyaluronic acid (HA) on adipose-derived stem cells (ASC) in order to consider the possibility of their combined used in the treatment of knee arthrosis.

Adhered bacteria on titanium surfaces are able to decrease its corrosion potential and impedance values at the lowest frequencies. This result points to the detrimental influence of the biofilm on the passive film formed on the surfaces, independently on the surface finishes.

Titanium is one of the most used metallic biomaterials for biological and implant applications. The spontaneous formation of a protective passive film around 2–5 nm thick, make titanium unique as a biomaterial for implants. Its composition has been described by a three-layer model: TiO2/Ti2O3/TiO and its stability is ultimately responsible for the success of osseointegrated titanium implants. The cases of breakdown of the protective passive film are associated with highly acidic environments induced by bacterial biofilms and/or inflammatory processes that lead to localized corrosion of titanium and, in extreme cases, implant failure. Bearing in mind that the surface design of a titanium implant is a key element involved in the healing mechanisms at the bone-implant interface, the surface modifications have sought to enhance the biomechanical anchorage of the implant and promote osseointegration at the cell-biomolecular level. However, little attention has been paid to the effects of these surface modifications in the microbiologically induced corrosion (MIC). The aim of this work is to evaluate the potential for MIC of titanium in the short term under viable bacterial cells of Streptococcus mutansas a representative microorganism of oral biofilm considered to be a highly cariogenic pathogen.

Discs of 64 mm²surface area of commercially pure titanium, grade 4, were supplied by Biotechnology Institute (BTI, Vitoria, Spain). Four surface treatments were studied: two acid etchings (low roughness, opN and high roughness, opV). In addition, acid etched plus anodic oxidation (opNT). For comparative purposes, two surface finishes have been included: high roughness – corresponding with sandblasting-large grit plus acid (SLA); and, as-machined titanium (mach). The oral strain used for assessing the biofilm formation on the corrosion behavior of Ti surfaces was Streptococus mutansATCC 25175, obtained from the Spanish Type Culture Collection (CECT). The study of MIC from Streptococcus mutanson surfaces of Ti was carried out in an electrochemical cell specifically designed and patented by some of the present authors [1]. A three set up configuration of the electrochemical cell was used in the experiments. The measurement of the corrosion potential and electrochemical impedance was performed at different periods of incubation of bacteria: 2, 7, 15, 21 and 28 days.

Out Slight but continuous decrease in the corrosion potential and impedance values at the lowest frequencies indicate the deleterious influence of the biofilm on the passive film formed on the surfaces, independently on the surface finishes.

This research suggests that the most appropriate surface modification for the dental implant portion at the bone level would be the acid etched of high roughness (opV) surface.

The surface of any implant device plays an important role in their biocompatibility. After implantation, the physico-chemical surface properties of any biomaterial determine its good/bad response against protein adsorption, cell attachment and proliferation and bacterial adhesion [1]. In this sense, the knowledge of hydrophobicity and surface tension of any new-developed biomaterial is an added value for the final product. Polymeric implants, among which are poly-D-Lactic acid (PLDA), are well characterized biodegradable biomaterials that have been proposed as an alternative to metallic implants for fracture fixation. However, their use in the clinical practice has been limited due to insufficient osseointegration and adverse tissue reactions. Recently it has been demonstrated the feasibility of introducing Mg particles within the PLDA matrix as a new strategy to improve the bioactivity and mechanical properties of PLDA whereas simultaneously modulating the degradation rate of Mg [2]. In this work, the surface of new amorphous and crystalline composites of PLDA with two different Mg concentrations are characterized in terms of hydrophobicity and surface tension.

Amorphous and crystalline PLDA from Natureworks were reinforced with Mg particles through a processing route that contained four different stages: drying, hot extrusion, grinding and compression moulding. Two different Mg concentration were used: 1 wt.% and 10 wt.% Hydrophobicity was obtained by goniometry using water as probe liquid (θ_W). The surface tension was determined through the Young Equation using water, formamide and diiodomethane as probe liquids. Van Oss approach was used to split the surface tension into the Lifshitz-van der Waals component (γ^LW) and acid-base component (γ^AB). The acid-base was also divided into the electron-donor (γ⁻) and electron-acceptor parameters (γ⁺).

The water contact angle was similar in amorphous and crystalline samples. Mg always reduced the θ_W value, no matter the Mg concentration used. Reductions were similar for both Mg concentrations. The surface tension in amorphous samples was comprised between 26 and 36 mJ/m² and in crystalline samples was between 30 and 36 mJ/m². Although values were very similar, the deviations observed for crystalline samples were always smaller than for amorphous. An important effect of Mg in the composites was the increase in the parameter γ-.

Mg addition makes the polymer less hydrophobic. The increase of γ⁻ may be related to an increase in the negative surface charge of Mg samples. The hydrophobic reduction plus the more negative surface could impair the bacterial approach and further adhesion to the surface of the new composites, which implies an advance in the fight against infections.

Purpose: To understand the epidemiology and risk factors of an osteoporotic hip fracture in a non-elderly patient.

Methods: Retrospective study covering the period 1999–2004, assessing individual and family history, fracture type, hospital stay, time until surgery, type of treatment and possible study or treatment of bone fragility.

Results: 38 cases. 23 patients (60.5%) presented some risk factor related to osteoporosis: enolism 7, liver pathology 3, neuromuscular disease 13, steroid treatment 4 and anticonvulsant 3. Seven patients (18.4%) presented some type of psychiatric disorder. Mean hospitalisation time: 13 days. Time until surgery: 3 days. Fracture type: 20 (52.6%) pertrochanteric and 16 (42.10%) subcapital. Treatment: cannulated screws in 11 cases (29%), screw and plate in 21 (55.2%). We found no diagnosis of osteoporosis or related indications in the admission reports except in one patient. Patients over 50: hip fracture incidence 161.21/100,000 inhabitants, pertrochanteric in 54.9% and subcapital in 45.1%*.

*

A Torrijos, C Ojeda. Area 5 hip study group, La Paz Hospital

Conclusions:

Hip fractures resulting from low-energy trauma are uncommon in the population under the age of 50.

Aims: The purpose of this study is to evaluate the functional recovery and mortality after the sequential fracture of both hips in elderly patients. Methods: Eight hundred forty-two patients (over 64 years of age) with hip fractures (nonpathologic) consecutively admitted to our hospital between January 1, 1999, and December 31, 2001, were included in this prospective study. A total of 765 were admitted of their þrst hip fracture, and the other 77 patients had a second contralateral fracture. All patients were identiþed at the time of admission, had fracture treatment and were followed untill six months or death. Information of complications and postinjury function was collected. Differences between the two groups were explored in contingency tables. Results: Most recurrent hip fractures (90%) are the same pattern the þrst contralateral fracture was. Functional recovery, postoperative complications and the length of stay of the patients affected by recurrent fracture were similar to the ones of the patients suffering from a single fracture. Hemoglobin level at admittance was 13 g/dl (mean) for single group and 12 g/dl (mean) for recurrent group; blood transfusion was needed for 30% from the single group and 50% from the recurrent group. Six months mortality was 17% for recurrent group and 28% for single group (p=0.033). Conclusions: Our data suggest that the functional recovery in elderly patients with hip fractures is not inßuenced by a previous fracture of the contralateral hip. Lower mortality after recurrent hip fracture shows us older patients and those with more concomitant diseases died before suffering the second fracture.

Introduction and Objectives: This is a retrospective radiographic study of results of surgical correction of thoracolumbar and King I scoliosis using segmental instrumentation.

Materials and Methods: This study includes 44 patients (41 female, 3 male) with an average age of 16.8 years (12-40) and 5.9 years average progression. The number of instrumented levels was 5.1 (4–7). Curve magnitude, T1–S1 imbalance, and the angles of the instrumented zone were measured using teleradiographic studies with an anteroposterior view. Thoracic kyphosis and lumbar lordosis were measured in the sagittal plane, and the thoracic and lumbar regions were measured in the instrumented area.

Results: On the anteroposterior view, average magnitude of principal preoperative curve, postoperative curve, and final result was 48°, 11.9°, and 14.7°, respectively. A final correction of 69.3% was obtained. T1–S1 imbalance improved from an initial 2.1cm to 1.9cm postoperatively and a final result of 0.5cm. On the lateral view, preoperative, postoperative, and final thoracic kyphosis were 29.5°, 27.8°, and 30.4°, respectively. Average figures for lumbar lordosis were 59.2°, 55.6°, and 61.1°. The instrumented thoracic zone went from 0.8° kyphosis preoperatively to 4.7° final kyphosis, and the lumbar area of instrumentation went from 9.7° preoperative lordosis to a final angle of 10.4°.

Discussion and Conclusions: In our experience, correction of thoracolumbar and King I scoliosis using anterior instrumentation has given good results, obtaining an initial 75% correction of the principal curve and an average loss of only 3° on follow-up. In the sagittal plane, there is no loss of kyphosis and lordosis, both of which are within normal physiological ranges. Thoracic kyphosis was increased 3.9° in the instrumented zone, and although instrumented lordosis did not improve, a kyphotic effect was observed.