Modulating Bioglass Concentration in 3D Printed Poly(propylene fumarate) Scaffolds for Post-Printing Functionalization with Bioactive Functional Groups.

Poly(propylene fumarate) (PPF) has shown potential for the treatment of bone defects as it can be 3D printed into scaffolds to suit patient-specific needs with strength comparable to that of bone. However, the lack of specific cell attachment and osteogenic signaling moieties have limited their utility as it is necessary to provide these signals to aid in bone tissue formation. To address this issue and provide a platform for functionalization, Bioglass (∼1-2 µm) microparticles have been incorporated into PPF to create a 3D printable resin with concentrations ranging from 0 to 10 wt %. The zero-shear viscosity of PPF-Bioglass resins increased proportionally from 0 to 2.5 wt % Bioglass, with values of 0.22 and 0.34 Pa·s, respectively. At higher Bioglass concentrations, 5 and 10 wt %, the resin viscosity increased to 0.44 and 1.31 Pa·s, exhibiting a 2- and 6-fold increase from the 0 wt % Bioglass resin. Despite this increase in viscosity, all resins remained printable with no print failures. In addition, the surface available Bioglass can tether catechol containing molecules for postprinting functionalization. Analysis of PPF-Bioglass functionalization using a catechol dye analyte shows functionalization increases with Bioglass concentration, up to 157 nmol/cm2, and demonstrates it is possible to modulate functionalization. This presents a versatile and highly translationally relevant strategy to functionalize 3D printed scaffolds post printing with a diverse array of functional species.

Influence of Electrical Field Collector Positioning and Motion Scheme on Electrospun Bifurcated Vascular Graft Membranes.

Currently, electrospinning membranes for vascular graft applications has been limited, due to random fiber alignment, to use in mandrel-spun, straight tubular shapes. However, straight, circular tubes with constant diameters are rare in the body. This study presents a method to fabricate curved, non-circular, and bifurcated vascular grafts based on electrospinning. In order to create a system capable of electrospinning membranes to meet specific patient needs, this study focused on characterizing the influence of fiber source, electrical field collector position (inside vs. outside the mandrel), and the motion scheme of the mandrel (rotation vs. rotation and tilting) on the vascular graft membrane morphology and mechanical properties. Given the extensive use of poly(ε-caprolactone) (PCL) in tubular vascular graft membranes, the same material was used here to facilitate a comparison. Our results showed that the best morphology was obtained using orthogonal sources and collector positioning, and a well-timed rotation and tilting motion scheme. In terms of mechanical properties, our bifurcated vascular graft membranes showed burst pressure comparable to that of tubular vascular graft membranes previously reported, with values up to 5126 mmHg. However, the suture retention strength shown by the bifurcated vascular graft membranes was less than desired, not clinically viable values. Process improvements are being contemplated to introduce these devices into the clinical range.

Optimization of photocrosslinkable resin components and 3D printing process parameters.

The role of 3D printing in the biomedical field is growing. In this context, photocrosslink-based 3D printing procedures for resorbable polymers stand out. Despite much work, more studies are needed on photocuring stereochemistry, new resin additives, new polymers and resin components. As part of these studies it is vital to present the logic used to optimize the amount of each resin constituent and how that effects printing process parameters. The present manuscript aims to analyze the effects of poly(propylene fumarate) (PPF) resin components and their effect on 3D printing process parameters. Diethyl fumarate (DEF), bisacylphosphine oxide (BAPO), Irgacure 784, 2-hydroxy-4-methoxybenzophenone (HMB) and, for the first time, in biomedical 3D printing, ethyl acetate (EA), were the resin components under investigation in this study. Regarding printing process parameters, Exposure Time, Voxel Depth, and Overcuring Depth were the parameters studied. Taguchi Design of Experiments was used to search for the effect of varying these resin constituent concentrations and 3D printing parameters on the curing behavior of 3D printable PPF resins. Our results indicate that resins with higher polymer cross-link density, especially those with a higher content of PPF, are able to be printed at higher voxel depth and with greater success (i.e., high yield). High voxel depth, as long as it does not sacrifice required resolution, is desirable as it speeds printing. Nevertheless, the overall process is governed by the correct setup of the voxel depth in relation to overcuring depth. In regards to resin biocompatibility, it was observed that EA is more effective than DEF, the material we had previously relied on. Our preliminary in vitro cytotoxicity tests indicate that the use of EA does not reduce scaffold biocompatibility as measured by standard cytotoxicity testing (i.e., ISO 10993-5). We demonstrate a workpath for resin constituent concentration optimization through thin film tests and photocrosslinkable process optimization. STATEMENT OF SIGNIFICANCE: We report here the results of a study of photo-crosslinkable polymer resin component optimization for the 3D printing of resorbable poly(propylene fumarate) (PPF) scaffolds. Resin additives are initially optimized for PPF thin film printing. Once those parameters have been optimized the 3D printing process parameters for PPF objects with complex, porous shapes can be optimized. The design of experiments to optimize both polymer thin films and complex porous resorbable polymer scaffolds is important as a guess and check, or in some cases a systematic method, are very likely to be too time consuming to accomplish. Previously unstudied resin components and process parameters are reported.

Surface Finish and Back-Wall Dross Behavior during the Fiber Laser Cutting of AZ31 Magnesium Alloy.

Magnesium alloys are of increasing interest in the medical industry due to their biodegradability properties and better mechanical properties as compared to biodegradable polymers. Fiber laser cutting of AZ31 magnesium alloy tubes was carried out to study the effect of cutting conditions on wall surface roughness and back-wall dross. During the experiments, an argon gas chamber was adapted in order to avoid material reactivity with oxygen and thus better control the part quality. A surface response methodology was applied to identify the significance of pulse overlapping and pulse energy. Our results indicate minimum values of surface roughness (Ra < 0.7 µm) when the spot overlapping is higher than 50%. A back-wall dross range of 0.24% to 0.94% was established. In addition, a reduction in back-wall dross accumulations was obtained after blowing away the dross particles from inside the tube using an argon gas jet, reaching values of 0.21%. Laser cutting experimental models show a quadratic model for back-wall dross related with the interaction of the pulse energy, and a linear model dependent on pulse overlapping factor for surface roughness.

Experiencia con OK-432 en malformaciones vasculares linfáticas en un hospital del norte de México / Experience with OK-432 in lymphatic vascular malformations in a hospital from northern Mexico

Resumen Introducción: Las malformaciones vasculares linfáticas (MVL), anteriormente llamadas linfangiomas, son malformaciones congénitas que se presentan en uno de cada 6,000 a 16,000 nacimientos. El sistema de clasificación más útil para el manejo del linfangioma se basa en el tamaño de los quistes. La resolución espontánea es infrecuente, por lo que el tratamiento expectante no se recomienda. El tratamiento clásico es la cirugía de escisión, pero puede afectar a estructuras vecinas o haber recidivas, por lo que se empezaron a estudiar sustancias esclerosantes, como el OK-432. La mayoría de los estudios incluyen pocos pacientes; los más grandes realizados en México se enfocan a lesiones específicas (macroquísticas) o únicamente a una región anatómica. Hasta la fecha, no existen estudios del uso de este fármaco en la población del norte de México. Método: Se describe la experiencia con OK-432 mediante un estudio retrospectivo, descriptivo, en los pacientes con MVL, de 2011 a 2016, en un hospital de referencia del norte de México. Resultados: Veintiséis pacientes con MVL recibieron tratamiento con OK-432. La mayoría fueron macroquísticos (69%), microquísticos (19%) y mixtos (12%). Del total de pacientes, 11 presentaron curación total. El 72% de la población estudiada tuvo una reducción de > 50% del tamaño de las lesiones con solo dos aplicaciones de tratamiento; no se presentaron recidivas. Se reportaron complicaciones en dos pacientes (hiperpigmentación de la piel). Conclusiones: El manejo con OK-432 demostró ser efectivo para el tratamiento de las MVL en un hospital de referencia del norte de México.

Abstract Background: Lymphatic vascular malformations (LVM) or formerly called lymphangiomas are congenital malformations present in about 1 out of 6000 to -16000 births. The most relevant classification system for lymphangioma management is based on the size of the cysts. Spontaneous resolution is uncommon; thus, expectant management is not recommended. The classic treatment is excisional surgery, but it can affect adjacent structures or have relapses, so, sclerosing substances like OK-432 are being studied. The majority of the studies are small in number of patients and are from Japan; the largest studies in Mexico are focused on specific lesions (macrocystic) or a determined anatomical region. To date, there are no studies of the population of the north of Mexico. Methods: The experience with OK-432 was described through a retrospective, descriptive study in patients with LVM, from 2011 to 2016, in a reference hospital of northern Mexico. Results: A total of 26 patients with LVM were treated with OK-432. The majority of the lesions were macrocystic (69 %), microcystic (19 %) and mixed (12 %). From the total number of patients, 11 fully healed, and 72 % of the study population had >50 % reduction in lesion size, with only 2 applications. There were no recurrences. Complications were reported in 2 patients who had skin hyperpigmentation. Conclusions: OK-432 probed to be an effective treatment for LVM in a reference hospital in the north of Mexico.

Noncholestatic acute hepatocellular injury following candesartan administration.

Arterial hypertension is a highly manageable disorder due to a variety of drugs available for its treatment. Since the late 1990s, angiotensin II receptor blockers have been widely prescribed, achieving appropriate control in patients' blood pressure. Few cases of serious adverse effects have been reported to date. Here, we present a case of acute hepatocellular injury secondary to candesartan administration. Further studies should be performed in patients who present with this adverse effect, in order to prevent more serious outcomes.

Endoscopic gastric polypectomy assisted by laparoscopy for giant gastric and duodenal lesion treatment: Case series from two centres.

BACKGROUND: Endoscopy has developed rapidly, generating new challenges. Today, there are several procedures done endoscopically with very good results. In the past, the assisted laparoscopic colon polypectomy has been described, reducing the morbidity of a bigger procedure. Nonetheless, little has been said about the use of hybrid surgery in the management of gastric or duodenal polyps. OBJECTIVES: Evaluating the safety and efficacy of the assisted laparoscopic gastric endoscopic polypectomy. PATIENTS AND METHODS: A retrospective review of the database at our two centres was performed from 1996 to 2014. Thirteen patients were found in whom an assisted laparoscopic gastric or duodenal endoscopic tumour resection was performed. RESULTS: Thirteen patients, eight males and five females, with a median age of 61 years and average body mass index of 29.3. The procedure was done effectively and no need for further procedures was required for any patient. No complications were reported in the early post-operative period. CONCLUSIONS: The study shows that assisted laparoscopic gastric endoscopic polypectomy is a feasible and safe procedure that can be used for the management of giant polyps, which cannot be resected with the classical endoscopic polypectomy reducing the morbidity and complications associated with larger procedures.

Sobetirome: the past, present and questions about the future.

Sobetirome binds selectively to the main hepatic form of thyroid hormone (TH) receptor, TRß1, compared to TRα1, which is principally responsible for thyrotoxic effects on heart, muscle and bone. Sobetirome also preferentially accumulates in liver. It was originally envisaged that sobetirome could be used to stimulate hepatic pathways that lower cholesterol without harmful side effects and might be used in conjunction with statins. Indeed, sobetirome progressed through preclinical animal studies and Phase I human clinical trials with excellent results and without obvious harmful side effects. Despite the fact that cardiovascular disease remains a major cause of mortality and that new therapies are desperately needed, it is unlikely that sobetirome will progress in further human clinical trials in the near future. The emergence of alternative cholesterol-lowering therapeutics may render selective thyromimetics redundant. Further, fears of thyrotoxic effects in the heart and emergence of cartilage defects in dogs after long-term use of eprotirome, a similar though not identical compound, has reduced enthusiasm for this strategy. We argue that it is nevertheless important to explore uses of sobetirome in humans; more treatment strategies would help patients with hard-to-treat dyslipidemias. Sobetirome may also have additional applications in orphan indications and short-term controlled weight loss.

Thyroid hormone induction of human cholesterol 7 alpha-hydroxylase (Cyp7a1) in vitro.

Thyroid hormone (TH) modulates serum cholesterol by acting on TH receptor ß1 (TRß1) in liver to regulate metabolic gene sets. In rodents, one important TH regulated step involves induction of Cyp7a1, an enzyme in the cytochrome P450 family, which enhances cholesterol to bile acid conversion and plays a crucial role in regulation of serum cholesterol levels. Current models suggest, however, that Cyp7a1 has lost the capacity to respond to THs in humans. We were prompted to re-examine TH effects on cholesterol metabolic genes in human liver cells by a recent study of a synthetic TH mimetic which showed that serum cholesterol reductions were accompanied by increases in a marker for bile acid synthesis in humans. Here, we show that TH effects upon cholesterol metabolic genes are almost identical in mouse liver, mouse and human liver primary cells and human hepatocyte cell lines. Moreover, Cyp7a1 is a direct TR target gene that responds to physiologic TR levels through a set of distinct response elements in its promoter. These findings suggest that THs regulate cholesterol to bile acid conversion in similar ways in humans and rodent experimental models and that manipulation of hormone signaling pathways could provide a strategy to enhance Cyp7a1 activity in human patients.