Inanimate 3D printed model for thoracoscopic repair of esophageal atresia with tracheoesophageal fistula.

Background: Thoracoscopic repair of esophageal atresia (EA) and tracheoesophageal fistula (TEF) poses significant technical challenges. This study aimed to develop an inexpensive, reusable, high-fidelity synthetic tissue model for simulating EA/TEF repairs and to assess the validity of the simulator. Methods: By using 3D printing and silicone casting, we designed an inexpensive and reusable inanimate model for training in thoracoscopic EA/TEF repair. The objective was to validate the model using a 5-point Likert scale and the Objective Structured Assessment of Technical Skills (OSATS) to evaluate participants' surgical proficiency. Results: A total of 18 participants (7 medical students, 4 pediatric surgery trainees, and 7 experienced surgeons), after being instructed and trained, were asked to perform TEF ligation, dissection, as well as esophageal anastomosis using six sliding knots on the EA/TEF simulator. All participants in the expert group completed the task within the 120-minute time limit, however only 4 (57%) participants from the novice/intermediate completed the task within the time limit. There was a statistically significant difference in OSATS scores for the "flow of task" (p = 0.018) and scores for the "overall MIS skills" (p = 0.010) task distinguishing between novice and intermediates and experts. The simulator demonstrated strong suitability as a training tool, indicated by a mean score of 4.66. The mean scores for the model's realism and the working environment were 4.25 and 4.5, respectively. Overall, the face validity was scored significantly lower in the expert group compared to the novice/intermediate groups (p = 0.0002). Conclusions: Our study established good face and content validity of the simulator. Due to its reusability, and suitability for individual participants, our model holds promise as a training tool for thoracoscopic procedures among surgeons. However, novices and trainees struggled with advanced minimally invasive surgical procedures. Therefore, a structured and focused training curriculum in pediatric MIS is needed for optimal utilization of the available training hours.

Utilisation of three-dimensional printed heart models for operative planning of complex congenital heart defects.

BACKGROUND AND AIM: To evaluate the accuracy of the three-dimensional (3D) printing of cardiovascular structures. To explore whether utilisation of 3D printed heart replicas can improve surgical and catheter interventional planning in patients with complex congenital heart defects. METHODS: Between December 2014 and November 2015 we fabricated eight cardiovascular models based on computed tomography data in patients with complex spatial anatomical relationships of cardiovascular structures. A Bland-Altman analysis was used to assess the accuracy of 3D printing by comparing dimension measurements at analogous anatomical locations between the printed models and digital imagery data, as well as between printed models and in vivo surgical findings. The contribution of 3D printed heart models for perioperative planning improvement was evaluated in the four most representative patients. RESULTS: Bland-Altman analysis confirmed the high accuracy of 3D cardiovascular printing. Each printed model offered an improved spatial anatomical orientation of cardiovascular structures. CONCLUSIONS: Current 3D printers can produce authentic copies of patients` cardiovascular systems from computed tomography data. The use of 3D printed models can facilitate surgical or catheter interventional procedures in patients with complex congenital heart defects due to better preoperative planning and intraoperative orientation.

The physical properties of lipid monolayers and bilayers containing calixarenes sensitive to cytochrome c.

We studied physical properties of the monolayers and bilayer lipid membranes (BLM) formed by calix[6]arene carboxylic acid derivative (CX) and its mixtures with diphytanoylphosphatidylcholine (DPhPC) by means of measurement surface pressure, surface dipole potential and electrostriction. CX forms stable monolayers at an air-water interface and complexes in mixed monolayers contained DPhPC. Calixarenes increase the elastic moduli of lipid monolayers as well as BLM. Cytochrome c (cyt c) specifically binds to CX by incorporation of the amino groups of lysine residues at the protein surface. This binding affected the physical properties of CX monolayers depending on their initial surface pressure. Addition of cyt c into the water subphase induced increase of surface pressure of CX monolayers at relatively low initial pressure (15 mN/m) when monolayer was in liquid expanded state (LE). This may be due interaction of positively charged cyt c with negatively charged carboxylic groups of CX and also by its penetration into the air-water interface. However, much subtle changes were observed for higher initial surface pressure (20 and 35 mN/m) when monolayer is in liquid condensed (LC) and solid (S) state, respectively. Lysine induced substantially lower changes in surface pressure in comparison with that of cyt c.

Cationic carbosilane dendrimers-lipid membrane interactions.

The aim of this work was to study interactions between cationic carbosilane dendrimers (CBS) and lipid bilayers or monolayers. Two kinds of second generation carbosilane dendrimers were used: NN16 with Si-O bonds and BDBR0011 with Si-C bonds. The results show that cationic carbosilane dendrimers interact both with liposomes and lipid monolayers. Interactions were stronger for negatively charged membranes and high concentration of dendrimers. In liposomes interactions were studied by measuring fluorescence anisotropy changes of fluorescent labels incorporated into the bilayer. An increase in fluorescence anisotropy was observed for both fluorescent probes when dendrimers were added to lipids that means the decreased membrane fluidity. Both the hydrophobic and hydrophilic parts of liposome bilayers became more rigid. This may be due to dendrimers' incorporation into liposome bilayer. For higher concentrations of both dendrimers precipitation occurred in negatively charged liposomes. NN16 dendrimer interacted stronger with hydrophilic part of bilayers whereas BDBR0011 greatly modified the hydrophobic area. Monolayers method brought similar results. Both dendrimers influenced lipid monolayers and changed surface pressure. For negatively charged lipids the monitored parameter changed stronger than for uncharged DMPC lipids. Moreover, NN16 dendrimer interacted stronger than the BDBR0011.

Characterization of hydrophobic interaction and antioxidant properties of the phenothiazine nucleus in mitochondrial and model membranes.

The antioxidant properties of the phenothiazine nucleus (PHT) associated with mitochondrial membranes and liposomes were investigated. PHT exhibited hydrophobic interaction with lipid bilayers, as shown by the quenching of excited states of 1-palmitoyl-2[10-pyran-1-yl)]-decanoyl-sn-glycero-3-phophocholine (PPDPC) incorporated in phosphatidylcholine/phosphatidylethanolamine/cardiolipin liposomes, observed even in high ionic strength; and by the spectral changes of PHT following the addition of mitochondrial membranes. Inserted into bilayers, 5 microM PHT was able to protect lipids and cytochrome c against pro-oxidant agents and exhibited spectral changes suggestive of oxidative modifications promoted by the trapping of the reactive species. In this regard, PHT exhibited the ability to scavenge DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) free radical. PHT was also able to protect rat liver mitochondria against peroxide- and iron-induced oxidative damage and consequent swelling. At the concentration range in which the antioxidant properties were observed, PHT did not cause alterations in the membrane structure and function. This study contributes to the comprehension of the correlation structure and function of phenothiazines and antioxidant properties.

Screening for the drug-phospholipid interaction: correlation to phospholipidosis.

Phospholipid bilayers represent a complex, anisotropic environment fundamentally different from bulk oil or octanol, for instance. Even "simple" drug association to phospholipid bilayers can only be fully understood if the slab-of-hydrocarbon approach is abandoned and the complex, anisotropic properties of lipid bilayers reflecting the chemical structures and organization of the constituent phospholipids are considered. The interactions of drugs with phospholipids are important in various processes, such as drug absorption, tissue distribution, and subcellular distribution. In addition, drug-lipid interactions may lead to changes in lipid-dependent protein activities, and further, to functional and morphological changes in cells, a prominent example being the phospholipidosis (PLD) induced by cationic amphiphilic drugs. Herein we briefly review drug-lipid interactions in general and the significance of these interactions in PLD in particular. We also focus on a potential causal connection between drug-induced PLD and steatohepatitis, which is induced by some cationic amphiphilic drugs.

Assessment of drug-lipid complex formation by a high-throughput Langmuir-balance and correlation to phospholipidosis.

Phospholipidosis, the accumulation of phospholipids in cells, is a relatively frequent side effect of cationic amphiphilic drugs. In response to the industry need, several methods have been recently published for the prediction of the phospholipidosis-inducing potential of drug candidates. We describe here a high-throughput physicochemical approach, which is based on the measurement of drug-phospholipid complex formation observed by their effect on the critical micelle concentration (CMC) of a short-chain acidic phospholipid. The relative change due to the drug, CMC(DL)/CMC(L) provides a direct measure of the energy of the drug-phospholipid association, irrespective of the nature of the interaction. Comparison of results for 53 drugs to human data, animal testing, cell culture assays, and other screening methods reveals very good correlation to their phospholipidosis-inducing potential. The method is well suited for screening already in early phases of drug discovery.

Maxwell displacement current allows to study structural changes of gramicidin A in monolayers at the air-water interface.

We applied methods of measurement Maxwell displacement current (MDC) pressure-area isotherms and dipole potential for analysis of the properties of gramicidin A (gA) and mixed gA/DMPC monolayers at an air-water interface. The MDC method allowed us to observe the kinetics of formation of secondary structure of gA in monolayers at an air-water interface. We showed, that secondary structure starts to form at rather low area per molecule at which gA monolayers are in gaseous state. Changes of the MDC during compression can be attributed to the reorientation of dipole moments in a gA double helix at area 7 nm(2)/molecule, followed by the formation of intertwined double helix of gA. The properties of gA in mixed monolayers depend on the molar fraction of gA/DMPC. At higher molar fractions of gA (around 0.5) the shape of the changes of dipole moment of mixed monolayer was similar to that for pure gA. The analysis of excess free energy in a gel (18( ) degrees C) and in a liquid-crystalline phase (28( ) degrees C) allowed us to show influence of the monolayer structural state on the interaction between gA and the phospholipids. In a gel state and at the gA/DMPC molar ratio below 0.17 the aggregates of gA were formed, while above this molar ratio gA interacts favorably with DMPC. In contrast, for DMPC in a liquid-crystalline state aggregation of gA was observed for all molar fractions studied. The effect of formation ordered structures between gA and DMPC is more pronounced at low temperatures.

Study of gramicidin A--phospholipid interactions in Langmuir monolayers: analysis of their mechanical, thermodynamical, and electrical properties.

The mechanisms of interactions between gramicidin A (gA) and dimyristoylphosphatidylcholine (DMPC) in monolayers formed at the air-water interface were studied by analyzing their mechanical, thermodynamical, and electrical properties evaluated from measurements of pressure-area isotherms and of Maxwell displacement currents (MDC). A contactless method of recording MDC enabled us to monitor changes in the charge state of the monolayer-constituting molecules and to find the relation between a phase state of the monolayer and structural transitions of gA. The peptide-lipid interactions were quantified in terms of the excess of Gibbs free energy, excess entropy, as well as the molecular dipole moments at various gA/DMPC molar ratios, at various temperatures (in the gel phase and also in the liquid-crystalline phase of DMPC molecule), and at various surface pressures. It was found that the strongest interactions between gA and DMPC took place at the gA/DMPC molar ratio at around 0.25. At this monolayer composition, the phospholipids, via their carbonyl moieties, dominantly interact with the single helical gA, which mostly stands upright on the surface and is anchored by its C-terminus to the water surface, and prevent the formation of the intertwined helical gA dimers. The optimum ratio was confirmed also by anomalous electrical behavior of electrical dipole moments derived from MDC measurements.