Bioprinting a Synthetic Smectic Clay for Orthopedic Applications

Bioprinting technology has emerged as an important approach to bone and cartilage tissue engineering applications, because it allows the printing of scaffolds loaded with various components, such as cells, growth factors, or drugs. In this context, the bone has a very complex architecture containing highly vascularized and calcified tissues, while cartilage is avascular and has low cellularity and few nutrients. Owing to this complexity, the repair and regeneration of these tissues are highly challenging. Identification of the appropriate biomaterial and fabrication technologies can provide sustainable solutions to this challenge. Here, nanosized Laponite^® (Laponite is a trademark of the company BYK Additives Ltd.) has shown to be a promising material due to its unique properties such as excellent biocompatibility, facile gel formation, shear-thinning property (reversible physical crosslinking), high specific surface area, degrade into nontoxic products, and with osteoinductive properties. Even though Laponite and Laponite-based composite for 3D bioprinting application are considered as soft gels, they may therefore not be thought exhibiting sufficient mechanical strength for orthopedic applications. However, through the merging with suitable composite and, also by incorporation of crosslinking step, desired mechanical strength for orthopedic application can be obtained. In this review, recent advances and future perspective of bioprinting Laponite and Laponite composites for orthopedic applications are highlighted.

Biomineralization inspired engineering of nanobiomaterials promoting bone repair

A biomineralization processes is disclosed for engineering nanomaterials that support bone repair. The material was fabricated through a hot press process using electrospun poly(lactic acid) (PLA) matrix covered with hybrid composites of carbon nanotubes/graphene nanoribbons (GNR) and nanohydroxyapatite (nHA). Various scaffolds were devised [nHA/PLA, PLA/GNR, and PLA/nHA/GNR (1 and 3%)] and their structure and morphology characterized through Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), and Atomic force microscope (AFM). Moreover, thorough biocompatibility and toxicity studies were performed. Here, in vivo studies on toxicity and cytotoxicity were conducted in aqueous dispersions of the biomaterials at concentrations of 30, 60, and 120 μg/mL using the Allium cepa test. Further toxicity studies were performed through hemolysis toxicity tests and genotoxicity tests evaluating the damage index and damage frequencies of DNAs through comet assays with samples of the animals' peripheral blood, marrow, and liver. Additionally, the regenerative activity of the scaffolds was analyzed by measuring the cortical tibiae of rats oophorectomized implanted with the biomaterials. Biochemical analyzes [glutamic pyruvic transaminase (GPT), glutamic oxaloacetic transaminase (GOT), urea, calcium, phosphorus, and alkaline phosphatase (ALP)] were also performed on blood samples. The results suggested a toxicity and cytotoxicity level for the GNR biomaterials at a concentration of 60 and 120 μg/mL, but non-toxicity and cytotoxicity for the 30 μg/mL concentration. The scaffolds obtained at a concentration of 0.3 mg/cm² were not toxic in the hemolysis test and demonstrated no cytotoxicity, genotoxicity, and mutagenicity in the blood, marrow, and liver analyzes of the animals, corroborating data from the biochemical markers of GPT, GOT, and urea. Tissue regeneration was performed in all groups and was more pronounced in the group containing the combination of nHA/GNR (3%), which is consistent with the data obtained for the calcium, serum phosphorus, and ALP concentrations. Consequently, the study indicates that the engineered nanobiomaterial is a promising candidate for bone tissue repair and regenerative applications. STATEMENT OF SIGNIFICANCE: The scientific contribution of this study is the engineering of a synthetic hybrid biomaterial, in nanoscale by a pressing and heating process. A biodegradable polymeric matrix was covered on both sides with a carbonated hybrid bioceramic/graphene nanoribbons (GNR), which has hydrophilic characteristics, with chemical elements stoichiometrically similar to bone mineral composition. The nanomaterial displayed promising bone regeneration ability, which is the first example to be used in an osteoporotic animal model. Moreover, detailed biocompatibility and toxicity studies were performed on the nanomaterials and their compositions, which is of great interest for the scientific community.

Bioecological aspects of triatomines and marsupials as wild Trypanosoma cruzi reservoirs in urban, peri-urban and rural areas in the Western Brazilian Amazon

In the Amazon region, Trypanosoma cruzi transmission cycles involve a great diversity of Triatominae vectors and mammal reservoirs. Some Rhodnius spp. mainly inhabit palm trees that act as microhabitats for hosts and vectors. The current study aimed to describe aspects of the bio-ecology of the vectors and reservoirs of T. cruzi in relation to human populations resident near areas with large quantities of palm trees, in rural, peri-urban and urban collection environments, located in the Western Brazilian Amazon. Rhodnius pictipes and Didelphis marsupialis were respectively the most predominant vector and reservoir, with rates of 71% for R. pictipes and 96.5% for D. marsupialis. The vast majority of T. cruzi isolates clustered with TcI. The most prevalent haplotype was TcI COII1 (69.7%). Mauritia flexuosa and Attalea phalerata were the main ecological indicators of infestation by triatomines. Birds were the most common food source (27,71%). T. cruzi isolated from R. robustus has the haplotype HUM-13, previously detected in a chronic Chagas patient living in the same area. Our results demonstrate the relevance of this study, with the occurrence of elevated infection rates in animals, and suggest the importance of the Amazon zones where there is a risk of infection in humans.

Electrospun Nanofibrous Poly (Lactic Acid)/Titanium Dioxide Nanocomposite Membranes for Cutaneous Scar Minimization

Poly (lactic acid) (PLA) has been increasingly used in cutaneous tissue engineering due to its low cost, ease of handling, biodegradability, and biocompatibility, as well as its ability to form composites. However, these polymers possess a structure with nanoporous that mimic the cellular environment. In this study, nanocomposites are prepared using PLA and titanium dioxide (TiO2) (10 and 35%-w/w) nanoparticles that also function as an active anti-scarring agent. The nanocomposites were prepared using an electrospinning technique. Three different solutions were prepared as follows: PLA, 10% PLA/TiO2, and 35% PLA/TiO2 (w/w%). Electrospun PLA and PLA/TiO2 nanocomposites were characterized morphologically, structurally, and chemically using electron scanning microscopy, transmission electron microscopy, goniometry, and X-ray diffraction. L929 fibroblast cells were used for in vitro tests. The cytotoxic effect was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays. Versicam (VCAN), biglicam (BIG), interleukin-6 (IL6), interleukin-10 (IL-10), and type-1 collagen (COL1A1) genes were evaluated by RT-qPCR. In vivo tests using Wistar rats were conducted for up to 15 days. Nanofibrous fibers were obtained for all groups that did not contain residual solvents. No cytotoxic effects were observed for up to 168 h. The genes expressed showed the highest values of versican and collagen-1 (p < 0.05) for PLA/TiO2 nanocomposite scaffolds when compared to the control group (cells). Histological images showed that PLA at 10 and 35% w/w led to a discrete inflammatory infiltration and expression of many newly formed vessels, indicating increased metabolic activity of this tissue. To summarize, this study supported the potential of PLA/TiO2 nanocomposites ability to reduce cutaneous scarring in scaffolds.

Nanocomposite Hydrogel Produced from PEGDA and Laponite for Bone Regeneration

Herein, a nanocomposite hydrogel was produced using laponite and polyethylene-glycol diacrylate (PEGDA), with or without Irgacure (IG), for application in bone tissue regeneration. The nanocomposites were characterized by X-ray diffraction (XRD), Fourier-Transform infrared spectroscopy (FTIR), and thermal analysis (TG/DTG). The XRD results showed that the crystallographic structure of laponite was preserved in the nanocomposite hydrogels after the incorporation of PEGDA and IG. The FTIR results indicated that PEGDA polymer chains were entangled on laponite in hydrogels. The TG/DTG found that the presence of laponite (Lap) improved the thermal stability of nanocomposite hydrogel. The toxicity tests by Artemia salina indicated that the nanocomposite hydrogels were not toxic, because the amount of live nauplii was 80.0%. In addition, in vivo tests demonstrated that the hydrogels had the ability to regenerate bone in a bone defect model of the tibiae of osteopenic rats. For the nanocomposite hydrogel (PEGDA + Lap nanocomposites + UV light), the formation of intramembranous bone in the soft callus was more intense in 66.7% of the animals. Thus, the results presented in this study evidence that nanocomposite hydrogels obtained from laponite and PEGDA have the potential for use in bone regeneration.

Abstract 1379: IKKβ is a potential anti-angiogenic therapeutic target in KRAS-induced lung cancer

Activating mutations in KRAS are prevalent in cancer, but therapies targeted to oncogenic RAS have been ineffective to date. An alternative route for blocking RAS-driven oncogenic pathways is to target downstream effectors of RAS involved in promoting the oncogenic phenotype. One of the critical characteristics required for tumors to grow and progress is the ability of tumor cells to drive angiogenesis. Interestingly, oncogenic RAS promotes angiogenesis by upregulating the proangiogenic IL-8 cytokine, an NF-kB target gene; and recent studies have shown that oncogenic RAS also activates the NF-κB transcription factor pathway and that KRAS-induced lung tumorigenesis is suppressed by expression of a degradation-resistant form of the IκBα inhibitor or by genetic or pharmacological inhibition of IKKβ or deletion of the RELA/p65 subunit of NF-κB. Therefore, we hypothesized that IKKβ inhibition would reduce KRAS-induced angiogenesis and tumor progression. To test this hypothesis, we used genetic and pharmacological approaches to inhibit IKKβ in K-Ras mutant lung cancer cell lines. Treatment of KRAS-positive A549 e H358 lung cancer cells with the highly specific IKKβ inhibitor Compound A (CmpdA) or siRNA-mediated knockdown of IKKβ in these cells reduced expression and secretion of the proangiogenic IL-8 cytokine. We found that IKKβ targeting also reduced expression and secretion of VEGF, a growth factor involved in promoting angiogenesis, which is also regulated by NF-κB. Moreover, conditioned media from A549 and H358 cells with siRNA-mediated IKKβ knockdown reduced endothelial cell (HUVECS) migration. In order to ascertain whether IKKβ inhibition can directly affect endothelial cell function, we treated HUVECs with CmpdA, which also resulted in reduced HUVEC migration. To evaluate how IKKβ affects endothelial cell function in vivo, we used a mouse model of neonatal retinopathy, where pathological retinal angiogenesis is induced by transient exposure of neonatal mice to hyperoxic conditions. Angiogenesis was significantly reduced in this model when neonatal mice were treated with 3 doses of 10 mg/Kg CmpdA. Finally, IKKβ knockdown in A549 cells also reduced expression of MMP-2 and MMP9 metalloproteases and reduced A549 cell invasion. Taken together, these results suggest that IKKβ inhibition therapy may reduce tumor angiogenesis, as well as invasive properties of KRAS-induced lung tumors, thereby having the potential to result in a sustained therapeutic effect, particularly if combined with other therapeutic approaches.

Citation Format: Tatiana C. Lobo, Leila Magalhães, Laura Cardeal, Ricardo Giordano, Albert Baldwin, Daniela Bassères. IKKβ is a potential anti-angiogenic therapeutic target in KRAS-induced lung cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1379. doi:10.1158/1538-7445.AM2015-1379

[Reproducibility of head-up tilt test in patients with neurocardiogenic syncope]

PURPOSE

In order to identify the reproducibility of head-up tilt test, a second test one week later in 22 patients with a positive first test, was performed.

METHODS

The test was performed in a fasting state during the morning. The heart rate and blood pressure were monitored during 20 minutes in the supine position and then at 60 degrees for up to 40 minutes. The test were considered positive if the patient experienced syncope or pre-syncope with fall in systolic blood pressure > 30mmHg. The following aspects were evaluated: reproducibility of the positive response; the type of response (hypotension, asystole or hypotension plus bradycardia) and the time interval between tilt and the beginning of symptoms.

RESULTS

Eighteen (82%) patients had a second positive response; 14 (77.8%) of then had the same type of response; and 17 (94%) had syncope in similar time interval after tilt.

CONCLUSION

The head-up tilt testing has good reproducibility, although its use in the therapeutic management needs a longer period of evaluation.

[Diagnostic value of the tilt test in the evaluation of syncope of unknown origin. Preliminary results]

PURPOSE

In order to identify neurally mediated syncope, head-up tilt testing was performed in patients with recurrent unexplained syncope.

METHODS

The tests were performed in 125 patients in the fasting state, between 8:30 and 11:30 a.m. The blood pressure and heart rate were continuously monitored during 20 minutes in the resting state, and then, positioned at 60 degrees angle, for up to 40 minutes. A group of 20 patients with first negative test was submitted to intravenous isoproterenol in bolus of 2 micrograms every 2 minutes until symptoms occur or at a total dose of 8 micrograms. The test was considered positive when systolic blood pressure decreased at least 30 mmHg and the patient experimented syncope or pre-syncope.

RESULTS

In 52 patients the test was positive (41.6%), 63.5% of which had hypotension exclusively; 7.7% asystole; and 28.8% had hypotension and bradycardia. Nine of the 20 patients submitted to isoproterenol test were positive (45%). All patients recovered spontaneously after returning to supine position.

CONCLUSION

Head-up tilt testing is a safe and effective method for the identification of neurally mediated syncope.

[Radiofrequency catheter ablation of type I atrial flutter]

PURPOSE

To verify the efficacy and safety of the creation of a barrier with radiofrequency (RF) in the tricuspid annulus and the vena cava ostium (TA-IVC).

METHODS

Nine consecutive patients, 7 males, with age ranging from 36 to 76 years, with paroxysmal (7 patients) or permanent (2) type I atrial flutter (negative P wave in lead II, III and F) were submitted to RF ablation of TA-IVC istmo. One deflectable catheter with 4mm size tip was introduced into the right ventricle apex and pulled back to the inferior vena cava. When the atrial electrogram was detected the RF application was started. The RF was applied (20 watts during 60s) up to the proximity of inferior vena cava ostium. The end point was to stop atrial flutter. Then a vigorous atrial stimulation protocol, including isoproterenol infusion was used. In the next day, patients were submitted to transesophageal stimulation with the same protocol.

RESULTS

Atrial flutter was interrupted in all patients (100%) with 4 to 28 (mean 16.7 +/- 7.7) applications. Eight patients (88.8%) with one session and 1 (11.1%) with two sessions. The mean time spent to stop the atrial flutter with one application was 30.5 +/- 18.5s. There were no complications. After a mean follow up of 3 +/- 1.6 month all patients (100%) are asymptomatic. Two of them are taking propranolol to control symptomatic atrial and ventricular ectopic beats.

CONCLUSION

RF ablation of the TA-IVC istmo is efficient and safe in a short term follow up to interrupt and prevent re-induction and recurrence of type I atrial flutter.

[Sporotrichosis]

Sporotrichosis is the most common deep mycosis in many tropical regions. The etiologic agent, Sporotrichum schenckii, is easily cultivated but rarely seen in histologic sections.

Antiviral Activity of Electrospun Polyamide Ultrathin Fibers Against SARS-CoV-2 Variant

The development of new strategies to produce nanomaterials that can be used as personal protective equipment with antiviral activity and low toxicity is crucial. Electrospun ultrathin fibers have attracted considerable attention due to their potential for biomedical applications, including antiviral activity. Herein, we electrospun different grades of commercially available polyamide to produce ultrathin fibers and investigate their antiviral activity against SARS-CoV-2 Gamma lineage (P.1). We evaluated the morphology, chemical composition, and mechanical properties of the ultrathin fibers. We also investigated the in vitro cytotoxicity, hemolytic activity, and antiviral activity against SARS-CoV-2 Gamma lineage (P.1) of the developed ultrathin fibers. The ultrathin fibers had the following diameters and elastic moduli: (i) unmodified crude ultrathin polyamide (PAP) 0.59 μm and 3 MPa, (ii) polyamide Biotech (PAAM) 0.74 μm and 2.2 MPa, and (iii) Amni Virus-Bac OFF polyamide (PAVB) 0.69 μm and 1.06 MPa. The ultrathin PAP fibers showed increased antiviral activity compared to the other ultrathin fibers (PAAM and PAVB). None of the electrospun fibers showed cytotoxicity at the lowest concentration (12.5%). Additionally, hemolysis tests demonstrated a nonhemolytic profile for all fiber groups, reinforcing their biocompatibility and suitability for biomedical applications. The antiviral properties of the electrospun ultrathin PAP fibers, combined with their noncytotoxic and nonhemolytic characteristics, highlight their potential to be used as personal protection against SARS-CoV-2.

[Thrombolytic treatment in pulmonary thromboembolism in the postoperative period following heart surgery complicated by ischemic cerebrovascular attack]

A 69 years old man with pulmonary embolism early after coronary bypass surgery complicated by ischemic stroke received thrombolytic therapy. Reperfusion of the pulmonary artery was achieved. Conversion of the ischemic stroke to hemorrhagic infarction was observed at the CT-Scan without neurological impairment.

[Evaluation of cardiac manifestations in hypothyroidism: documentation of reversibility]

PURPOSE

To detect the cardiac manifestations due to the state of hypothyroidism and reversibility after euthyroidism.

PATIENTS AND METHODS

Thirteen patients with documented primary hypothyroidism were evaluated through the echocardiography and other noninvasive techniques. A new evaluation was performed six months after thyroid hormone therapy.

RESULTS

Most of the changes were reversed after the patients became euthyroid. The main finding was the echocardiographic measurement of the velocity of circumferential fiber shortening that showed a significant positive linear correlation with serum thyroid hormones.

CONCLUSION

These data demonstrate the existence of a hypothyroid cardiomyopathy.

[The pseudo-pacemaker syndrome]

We describe three cases of the pseudo-pacemaker syndrome. One of them due to selective fast pathway fulguration of atrioventricular nodal reentrant tachycardia and two others have occurred in spontaneous form. All cases were related with the presence of first-degree atrioventricular block and sinus node tachycardia. The treatment was done with complete atrioventricular block induction catheter ablation and permanent pacemaker implantation in two patients. In conclusion, the procedure of radiofrequency ablation to control AV nodal reentry tachycardia must preserve the fast nodal pathway in order to avoid the pseudo-pacemaker syndrome and this syndrome can spontaneously occur and must be considered during investigation of etiology of syncope.

[Salvage coronary angioplasty in a young patient with Takayasu arteritis and myocardial infarction]

A 16 year old boy with Takayasu's disease was admitted with myocardial infarction. Thrombolytic therapy with intravenous streptokinase showed no signs of reperfusion. Rescue angioplasty of the left descending coronary artery was performed with success.