microfluidic-chip-fabrication-and-method-to-detect-influenza

Microfluidic Chip Fabrication and Method to Detect Influenza

Fast  and effective diagnostics play an important role in controlling infectious  disease by enabling effective patient management and treatment. Here, we ...

Jejunostomy tubes can be placed endoscopically by means of percutaneous gastrostomy with jejunal extension (PEG-J) or by direct percutaneous jejunostomy. These 2 techniques were retrospectively compared in patients requiring long-term jejunal feeding.

Comparison of direct percutaneous endoscopic jejunostomy and PEG with jejunal extension.

Mediastinal lymphoma as a cause of tracheobronchial obstruction is uncommon, and a malignant tracheoesophageal fistula in the setting of mediastinal lymphoma is rare. Malignant tracheoesophageal fistulas are associated with pronounced morbidity and mortality. We describe a patient with mediastinal lymphomatous infiltration resulting in tracheal obstruction, esophageal obstruction, and tracheoesophageal fistula that were successfully palliated with combined airway and esophageal stent placement.

Combined tracheal and esophageal stenting for palliation of tracheoesophageal symptoms from mediastinal lymphoma.

Diarrhea and weight loss are common after pancreaticoduodenectomy, and arise from varying etiologies. An uncommon but important cause for these symptoms is the postoperative activation of silent celiac disease. We sought to describe the clinical presentation, diagnosis, treatment, and follow-up of a series of patients with silent celiac disease unmasked after pancreaticoduodenectomy, and to summarize the existing case reports on this association. A search of the electronic medical record at our institution was performed cross-referencing terms associated with celiac disease and pancreaticoduodenectomy for the years 1976-2004. Cases were then reviewed to ensure that no signs or symptoms attributable to celiac disease were present preoperatively. Seven patients were identified; five were male, and the median age was 56. All patients underwent surgery for a presumed pancreatic or ampullary malignancy. Six patients developed symptoms ultimately attributable to celiac disease immediately after pancreaticoduodenectomy, most commonly diarrhea and weight loss. A single patient had silent celiac disease incidentally diagnosed at pancreaticoduodenectomy that remained silent postoperatively on an unrestricted diet. Symptoms completely resolved in 4 of 6 patients after initiation of a gluten-free diet, with partial improvement in the remaining 2 patients. The median delay from pancreaticoduodenectomy to diagnosis of celiac disease in the 6 symptomatic patients was 6 months. Clinicians should consider celiac disease as a potential diagnosis in patients with failure to thrive and diarrhea after pancreaticoduodenectomy. This entity is uncommon, but may be under-recognized. The underlying mechanism may relate to an increased antigenic load secondary to postsurgical changes in intestinal physiology.

Silent celiac disease activated by pancreaticoduodenectomy.

Activation of the eukaryotic replicative DNA helicase, the Mcm2-7 complex, requires phosphorylation by Cdc7/Dbf4 (Dbf4-dependent kinase or DDK), which, in turn, depends on prior phosphorylation of Mcm2-7 by an unknown kinase (or kinases). We identified DDK phosphorylation sites on Mcm4 and Mcm6 and found that phosphorylation of either subunit suffices for cell proliferation. Importantly, prior phosphorylation of either S/T-P or S/T-Q motifs on these subunits is required for DDK phosphorylation of Mcm2-7 and for normal S phase passage. Phosphomimetic mutations of DDK target sites bypass both DDK function and mutation of the priming phosphorylation sites. Mrc1 facilitates Mec1 phosphorylation of the S/T-Q motifs of chromatin-bound Mcm2-7 during S phase to activate replication. Genetic interactions between priming site mutations and MRC1 or TOF1 deletion support a role for these modifications in replication fork stability. These findings identify regulatory mechanisms that modulate origin firing and replication fork assembly during cell cycle progression.

Mec1 is one of multiple kinases that prime the Mcm2-7 helicase for phosphorylation by Cdc7.

Often, modern diagnostic techniques require the isolation and purification of nucleic acids directly from patient samples such as blood or stool. Many diagnostic tests are being miniaturized onto micro-sized platforms and integrated into microfluidic devices due to the economies resulting from smaller sample and reagent volumes. Often, these devices perform sample preparation in series with the diagnostic tests. The sample preparation steps are vital in order to purify the desired genetic material from potential inhibitors that can interfere with the outcome of the test. There are various techniques used to selectively capture the nucleic acids while washing away potential contamination (proteins, enzymes, lipids, etc.). Two of the most common forms of selective capture are based on nucleic acid binding to silica surface or on the precipitation of nucleic acids with or without the presence of a carrier species. Each of these methods can be performed in liquid phase or in a solid support such as an extraction column. Here we discuss both methods and address microfluidic applications.

Purification of DNA/RNA in a microfluidic device.

The ability to increase the concentration of target analytes in a fixed sample volume can potentially lower the limit of detection for many biosensing techniques, and thus is key in sample preparation for infectious disease diagnosis. Concentration by evaporation is an effective method to achieve target enrichment. However, concentrating human samples, including blood and plasma, by evaporation-based methods is made challenging by high concentrations of proteins and electrolytes. Dehydration of the proteins causes the sample to turn into a gel, hindering further analysis. At the same time, decreasing the volume increases the overall concentration of electrolytes, causing bacterial or viral particle lysis, and making them more difficult to detect in affinity-based biosensors. Thus, we fabricated a microfluidic chip that incorporates both dialysis and concentration in a single design. The chip dialyzes the proteins from the plasma, while maintaining an appropriate concentration of electrolytes and concentrating the sample targets. The process to concentrate plasma or serum samples by a factor of 10 takes less than 30 minutes. As a proof-of-concept, we demonstrated the chip using a defective Human Immunodeficiency Virus (HIV). To distinguish patients on antiretroviral therapy who are failing therapy from those who are not, a diagnostic must be able to detect HIV in plasma down to at least 1000 particles per milliliter. For a number of technical reasons, it is difficult to get on-chip PCR reactions to reach this level of sensitivity, so concentration of HIV from lower viral load samples has the potential to improve the sensitivity of many types of molecular point-of-care viral load tests.

Article	Year
Comparison of direct percutaneous endoscopic jejunostomy and PEG with jejunal extension. Gastrointestinal endoscopy\| PubMed ID: 12447304	2002
Combined tracheal and esophageal stenting for palliation of tracheoesophageal symptoms from mediastinal lymphoma. Mayo Clinic proceedings. Mayo Clinic\| PubMed ID: 12479523	2002
Silent celiac disease activated by pancreaticoduodenectomy. Digestive diseases and sciences\| PubMed ID: 17373587	2007
Mec1 is one of multiple kinases that prime the Mcm2-7 helicase for phosphorylation by Cdc7. Molecular cell\| PubMed ID: 21070963	2010
Purification of DNA/RNA in a microfluidic device. Methods in molecular biology (Clifton, N.J.)\| PubMed ID: 23329456	2013
Sample concentration and purification for point-of-care diagnostics. Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference\| PubMed ID: 23366407	2012

Andy Fan

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