Red Blood Cells' Area Deformation as the Origin of the Photoplethysmography Signal

The origin of the photoplethysmography (PPG) signal is a debatable topic, despite plausible models being addressed. One concern revolves around the correlation between the mechanical waveform's pulsatile nature and the associated biomechanism. The interface between these domains requires a clear mathematical or physical model that can explain physiological behavior. Describing the correct origin of the recorded optical waveform not only benefits the development of the next generation of biosensors but also defines novel health markers. In this study, the assumption of a pulsatile nature is based on the mechanism of blood microcirculation. At this level, two interconnected phenomena occur: variation in blood flow velocity through the capillary network and red blood cell (RBC) shape deformation. The latter effect was qualitatively investigated in synthetic capillaries to assess the experimental data needed for PPG model development. Erythrocytes passed through 10 µm and 6 µm microchannel widths with imposed velocities between 50 µm/s and 2000 µm/s, according to real scenarios. As a result, the length and area deformation of RBCs followed a logarithmic law function of the achieved traveling speeds. Applying radiometric expertise on top, mechanical-optical insights are obtained regarding PPG's pulsatile nature. The mathematical equations derived from experimental data correlate microcirculation physiologic with waveform behavior at a high confidence level. The transfer function between the biomechanics and the optical signal is primarily influenced by the vasomotor state, capillary network orientation, concentration, and deformation performance of erythrocytes.

Field-Effect Transistors Based on Single-Layer Graphene and Graphene-Derived Materials

The progress of advanced materials has invoked great interest in promising novel biosensing applications. Field-effect transistors (FETs) are excellent options for biosensing devices due to the variability of the utilized materials and the self-amplifying role of electrical signals. The focus on nanoelectronics and high-performance biosensors has also generated an increasing demand for easy fabrication methods, as well as for economical and revolutionary materials. One of the innovative materials used in biosensing applications is graphene, on account of its remarkable properties, such as high thermal and electrical conductivity, potent mechanical properties, and high surface area to immobilize the receptors in biosensors. Besides graphene, other competing graphene-derived materials (GDMs) have emerged in this field, with comparable properties and improved cost-efficiency and ease of fabrication. In this paper, a comparative experimental study is presented for the first time, for FETs having a channel fabricated from three different graphenic materials: single-layer graphene (SLG), graphene/graphite nanowalls (GNW), and bulk nanocrystalline graphite (bulk-NCG). The devices are investigated by scanning electron microscopy (SEM), Raman spectroscopy, and I-V measurements. An increased electrical conductance is observed for the bulk-NCG-based FET, despite its higher defect density, the channel displaying a transconductance of up to ≊4.9×10-3 A V-1, and a charge carrier mobility of ≊2.86×10-4 cm2 V-1 s-1, at a source-drain potential of 3 V. An improvement in sensitivity due to Au nanoparticle functionalization is also acknowledged, with an increase of the ON/OFF current ratio of over four times, from ≊178.95 to ≊746.43, for the bulk-NCG FETs.

HT-29 Colon Cancer Cell Electromanipulation and Assessment Based on Their Electrical Properties

This study proposes a feasible approach for the rapid, sensitive, and label-free identification of cancerous cells based on dielectrophoretic (DEP) manipulation and electrical characterization. In this method, the concentration of target cells at the level of customized microelectrodes via DEP is first determined, followed by an electrical impedance evaluation. The study demonstrates the capacity of the methodology to electrically differentiate HT-29 cancer cells from healthy blood cells based on their impedance spectra. Within a higher frequency domain, the electrical impedance of trapped cancer cells was significantly lower compared with the normal ones. In order to evaluate the functionality and reproducibility of the proposed method, the influence of the DEP and EIS (electrical impedance spectroscopy) operating voltages on the electrical characterization of trapped HT-29 cells was analyzed.

Vertical Graphene-Based Biosensor for Tumor Cell Dielectric Signature Evaluation

The selective and rapid detection of tumor cells is of critical consequence for the theragnostic field of tumorigenesis; conventional methods, such as histopathological diagnostic methods, often require a long analysis time, excessive analytical costs, complex operations, qualified personnel and deliver many false-positive results. We are considering a new approach of an electrochemical biosensor based on graphene, which is evidenced to be a revolutionary nanomaterial enabling the specific and selective capture of tumor cells. In this paper, we report a biosensor fabricated by growing vertically aligned graphene nanosheets on the conductive surface of interdigitated electrodes which is functionalized with anti-EpCAM antibodies. The dielectric signature of the three types of tumor cells is determined by correlating the values from the Nyquist and Bode diagram: charge transfer resistance, electrical double layer capacity, Debye length, characteristic relaxation times of mobile charges, diffusion/adsorption coefficients, and variation in the electrical permittivity complex and of the phase shift with frequency. These characteristics are strongly dependent on the type of membrane molecules and the electromagnetic resonance frequency. We were able to use the fabricated sensor to differentiate between three types of tumor cell lines, HT-29, SW403 and MCF-7, by dielectric signature. The proposed evaluation method showed the permittivity at 1 MHz to be 3.63 nF for SW403 cells, 4.97 nF for HT 29 cells and 6.9 nF for MCF-7 cells.

Investigation of Multiphase Flow in a Trifurcation Microchannel-A Benchmark Problem

The evolution of an interface between two immiscible liquids in a three-branch symmetric microchannel is numerically and experimentally investigated. The main goals of the paper are to correlate the numeric data with the experimental results for the tested flow case and to assess the quality of the VOF procedure to trace the interface using the Fluent commercial code. The focus of the experiments was to characterize the dynamics of the oil–water interface formed in the vicinity of the bifurcation, at the entrance in the main microchannel of 400 microns width and 50 microns height. The oil core surrounded by water is visualized and micro-PIV measurements are performed in water. Experimental results qualitatively and quantitatively confirm the 3D numerical simulations. We propose the present investigated flow as a benchmark case for the study of the interface in a branching microchannel geometry.

Dielectrophoretic and Electrical Impedance Differentiation of Cancerous Cells Based on Biophysical Phenotype

Here, we reported a study on the detection and electrical characterization of both cancer cell line and primary tumor cells. Dielectrophoresis (DEP) and electrical impedance spectroscopy (EIS) were jointly employed to enable the rapid and label-free differentiation of various cancer cells from normal ones. The primary tumor cells that were collected from two colorectal cancer patients, cancer cell lines (SW-403, Jurkat, and THP-1), and healthy peripheral blood mononuclear cells (PBMCs) were trapped first at the level of interdigitated microelectrodes with the help of dielectrophoresis. Correlation of the cells dielectric characteristics that was obtained via electrical impedance spectroscopy (EIS) allowed evident differentiation of the various types of cell. The differentiations were assigned to a “dielectric phenotype” based on their crossover frequencies. Finally, Randles equivalent circuit model was employed for highlighting the differences with regard to a series group of charge transport resistance and constant phase element for cancerous and normal cells.

Wound healing applications of creams and "smart" hydrogels

Although superficial wounds are often easy to treat for healthy individuals, there are some more severe types of wounds (burns, ulcers, diabetic wounds, etc.) that are a challenge for clinicians. A good therapeutic result is based on the delivery of a treatment at the right time, for the right patient. Our goal was to sum up useful knowledge regarding wound healing and wound treatments, based on creams and hydrogels with various active ingredients. We concluded that both preparations have application in preventing infections and promoting healing, but their efficacy is clearly conditioned by the type, depth, severity of the wound and patient profile. However, due to their superior versatility and capability of maintaining the integrity and functionality of the active ingredient, as well as it is controlled release at site, hydrogels are more suited for incorporating different active ingredients. New wound healing devices can combine smart hydrogel dressings with physical therapies to deliver a more efficient treatment to patients if the indications are appropriate.

Soil Burial Biodegradation of PLA/Hydrolysed Collagen/Silver Manoparticles Bionanocomposites

In this study we evaluated the degradation behaviour of some polymeric bionanocomposites based on polylactic acid (PLA), hydrolysed collagen (HC) and silver nanoparticles (AgNPs) obtained by melt processing, by exposure at soil action for 30 days and 60 days. The quantification of the bionanocomposites� degradability was investigated by the weight loss determination, evaluation of the morphology-Scanning Electron Microscopy (SEM) measurements and the thermal parameters by Differential Scanning Calorimetry (DSC) measurements. From the obtained results we can observe that the polymeric composites based on hydrolysed collagen has degraded.

Detection of Circulating Tumor Cells Using Microfluidics

Metastasis is the main cause of death in cancer patients worldwide. During metastasis, cancer cells detach from the primary tumor and invade distant tissue. The cells that undergo this process are called circulating tumor cells (CTCs). Studies show that the number of CTCs in the peripheral blood can predict progression-free survival and overall survival and can be informative concerning the efficacy of treatment. Research is now concentrated on developing devices that can detect CTCs in the blood of cancer patients with improved sensitivity and specificity that can lead to improved clinical evaluation. This review focuses on devices that detect and capture CTCs using different cell properties (surface markers, size, deformability, electrical properties, etc.). We also discuss the process of tumor cell dissemination, the biology of CTCs, epithelial-mesenchymal transition (EMT), and several challenges and clinical applications of CTC detection.

Microbeads detection using spin-valve planar Hall effect sensors

In this paper we present a micromagnetic approach to describe the detection of magnetic nanobeads using planar Hall effect sensors. The magnetic beads polarized by a dc magnetic field generate a field, which can affect the magnetization state of spin-valve sensor, leading in principle, to a detectable signal. For magnetic nanobeads we assumed a superparamagnetic behaviour. Three detection geometries are discussed and some specific behaviours were highlighted by micromagnetic simulations. We found that when the polarising field is applied parallel with the sensor surface a very weak signal can be obtained. This is because at working fields, for which the magnetic nanobeads are magnetised, the sensor saturates. We identified other setups that can overcome this shortcoming and deliver a net signal.

A practical guide for the fabrication of microfluidic devices using glass and silicon

This paper describes the main protocols that are used for fabricating microfluidic devices from glass and silicon. Methods for micropatterning glass and silicon are surveyed, and their limitations are discussed. Bonding methods that can be used for joining these materials are summarized and key process parameters are indicated. The paper also outlines techniques for forming electrical connections between microfluidic devices and external circuits. A framework is proposed for the synthesis of a complete glass/silicon device fabrication flow.

[Stapled vs. hand-sewn colorectal anastomosis in complicated colorectal cancer--a retrospective study]

Emergens in colorectal pathology are in most cases by complications of cancer. The prognosis for colorectal cancer is poor when this pathology is addressed in emergency situations because, on one hand, of the organ specific structure, blood supply, septic content and, on the other hand, because of the special group of patients with this pathology: aged, immunosuppressed and with various comorbidities. The high rate of postoperative complications of these patients requires a specific management. The development and improvement of medical devices has brought to the surgeons new products among which mechanice devices for anastomoses. In this study we compared two groups of operated patients (with hand sutured and stapled anastomoses) who presented as emergences with complications of colorectal cancer.

MATERIAL AND METHOD

Retrospective clinical study with a total of 72 patients who underwent a colorectal resection procedure in emergency in our clinic (Emergency Hospital Bucharest) over a period of 2 years (2007-2008).

RESULTS

The 72 patients who required emergency surgery were randomly assigned to 2 categories according to the type of anastomosis: hand sutured (group 1, n = 34) and stapled (group 2, n = 38). Age, sex, comorbidities, and tumor staging were comparable in both groups. The emergency was represented by obstruction (56.94%), hemorrhage (8.33%) and perforation (34.72%). The mortality (10.5% vs. 8.8%) and orbidity rate (20.83% vs. 15.27%) was higher in the stapled anastomosis group. The average duration of the surgical procedure performed in emergency was also quantified and was 118 min. (group 2) vs. 236 min. (group 1) respectively.

CONCLUSION

Comparison did not disclose any significant difference in the number of complications in these two groups. Anastomosis is safe in emergency colorectal surgery and the reduction of the operative time may also improve the outcome of these patients.

[Laparoscopic approach in gallbladder agenesis--an intraoperative surprise]

INTRODUCTION

The congenital absence of the gallbladder in the absence of biliary atresia is extremely rare, world literature recognizing only 413 cases. The aim of this study is to clarify the diagnostic and therapeutic approach of this rare condition.

METHOD

There were retrospectively analyzed the first 2 cases of gallbladder agenesis admitted and surgically approached in the Emergency Hospital, Bucharest.

RESULTS

The first case (woman, 23 years old) had typically biliary complaints at admission, shrinked gallbladder and lithiasis on ultrasound. There was a laparoscopic approach but we didn't find any gallbladder. After a non-therapeutic laparoscopy the biliary symptoms disappeared. In the second case (woman, 52 years old) the admission was for upper abdominal quadrant colicative pain and the transparietal abdominal ultrasound showed chronic cholecystitis. Common bile duct dilatation was revealed during laparoscopy. After conversion to laparotomy there was performed intraoperative colangiography, but no other biliary pathology was revealed. The initial complaints also disappeared after surgery.

CONCLUSIONS

We find the laparoscopic approach an effective method for the diagnosis of gallbladder agenesis. Postoperative Magnetic Resonance Cholangiopancreatography represents a very useful imagistic tool to rule out an intrahepatic gallbladder.

The use of grafting material in rhinoseptoplasty

Grafting is one of the current range of instruments that rhinoplasticians deploy to achieve durable and desired aesthetic and functional outcomes. Grafts can be classified according to anatomical site and, in the vast majority of cases, they involve augmentation rhinoseptoplasty. Visible grafting material is used for aesthetic purposes and functional grafting may involve invisible grafts. This article reviews the more widely described and more common indications for grafts in rhinoseptoplasty. The authors' rhinoseptoplasty philosophy involves a preference for autogenous grafts rather than alloplastic implants to achieve both aesthetically and functionally favourable results, particularly in long-term follow-up. They also prefer grafts in an open approach, reserving graft insertion with an endonasal approach for selected cases. The rate of complications associated with grafting is very low. The aim of this paper is to discuss the relevant anatomy, functional purpose and terminology, and to describe the authors' philosophy for grafting in rhinoseptoplasty.

[Köhlmeier-Degos disease (Malignant Atrophic Papulosis): a cause of recurrent multiple intestinal perforations]

Malignant Atrophic Papulosis (MAP) or Degos disease is a very rare vasculopathy affecting multiple systems. When associated with gastrointestinal tract or central nervous system involvment, patients with Degos disease have a poor prognosis and a high mortality. We report a case of Degos disease with systemic involvement, which ultimately caused peritonitis, sepsis, and death, despite all treatment. A 29-year-old man was admitted in June 2007 on the surgical ward of our hospital with acute generalized abdominal pain and multiple skin lesions. The patient had an appendectomy at another hospital 6 weeks before the current presentation. The exploratory laparotomy showed 2 perforations of the ileum. After the initial procedure, the patient developed spontaneous recurrent perforations of the small bowel and suffered another 3 reoperations. Neuroradiologic reports described central and peripheral nervous system involvement with progressive clinical deterioration and a meningovascular pattern at cerebral MRI. Despite aggressive treatment the patient died 3 months after the first surgical intervention.

[Management for pseudoaneurysm of cystic artery with an arterio-biliary fistula after laparoscopic cholecystectomy: a rare case of hemobilia]

Although laparoscopic cholecystectomy is considered to be the gold standard for treatment for symptomatic cholelithiasis, it is associated with an increased risk of biliary and vascular injury compared to the traditional technique. Massive hemobilia is a rare but potentially life-threatening cause of upper gastrointestinal hemorrhage. Arterio-biliary fistula is an uncommon cause of hemobilia. We describe a case of cystic artery pseudo-aneurysm causing arterio-biliary fistula and presenting as severe melaena and cholangitis that occurred 7 months after laparoscopic cholecystectomy. Gastroduodenoscopy failed to establish the exact source of bleeding and hepatic artery angiography and selective embolization of the pseudo-aneurysm successfully controlled the bleeding. Pseudo-aneurysm of the hepatic artery is mostly iatrogenic due to biliary intervention, as demonstrated in this case. Transarterial embolization is considered the first line of intervention to stop the bleeding for most causes of hemobilia. Hemobilia is a rare complication that should be considered when managing patients with bleeding or jaundice even several months after laparoscopic cholecystectomy.

Hemodynamic consequences of continuous arteriovenous hemofiltration

Continuous arteriovenous hemofiltration (CAVH) is an extracorporeal treatment in which fluid, electrolytes, and low and middle molecular weight solutes are removed from the blood by ultrafiltration. It is efficacious in the management of acute or chronic renal failure complicated by fluid overload, and following surgery. In this study, cardiac filling pressures, cardiac indices, and BP were monitored in nine patients. A mean of 7 kg of fluid was removed in ten treatments without the induction of hypotension. In nine of ten treatments, cardiac index increased following fluid removal. An increment in myocardial pump function was noted even in patients with low output heart failure. This treatment differs from dialysis in its ability to remove large fluid volumes without compromising cardiac hemodynamics. In addition, CAVH may have a role in treating volume overload patients with renal insufficiency and heart failure resistant to pharmacologic intervention.