Inkjet-Printing Enzyme Inhibitory Assay Based on Determination of Ejection Volume.

An accurate, rapid, and cost-effective methodology for enzyme inhibitor assays is highly needed for large-scale screening to evaluate the efficacy of drugs at the molecular level. For the first time, we have developed an inkjet printing-based enzyme inhibition assay for the assessment of drug activity using a conventional inkjet printer composed of four cartridges. The methodology is based on the determination of the number of moles of the drug on the printed surface. The number of moles was quantified through the volume of substance ejected onto the printed surface. The volume ejected on the reaction spot was determined from the density of reagent ink solution and its weight loss after printing. A xanthine oxidase (XOD) inhibition assay was executed to quantitatively evaluate antioxidant activities of the drug based on the determination of the number of moles of the drug ejected by inkjet printing. The assay components of xanthine, nitro blue tetrazolium (NBT), superoxide dismutase (SOD)/drug, and XOD were printed systematically on A4 paper. A gradient range of the number of moles of SOD/drug printed on A4 paper could be successfully obtained. Because of the effect of enzyme activity inhibition, incrementally reduced NBT formazan colors appeared on the paper in a number-of-moles-dependent manner. The observed inhibitory mole (IM50) values of tested compounds exhibited a similar tendency in their activity order, compared to the IC50 values observed through absorption assay in well plates. Inkjet printing-based IM50 assessment consumed a significantly smaller reaction volume (by 2-3 orders of magnitude) and more rapid reaction time, compared to the well-plate-based absorption assay.

Phosphate Detection through a Cost-Effective Carbon Black Nanoparticle-Modified Screen-Printed Electrode Embedded in a Continuous Flow System.

An automatable flow system for the continuous and long-term monitoring of the phosphate level has been developed using an amperometric detection method based on the use of a miniaturized sensor. This method is based on the monitoring of an electroactive complex obtained by the reaction between phosphate and molybdate that is consequently reduced at the electrode surface. The use of a screen-printed electrode modified with carbon black nanoparticles (CBNPs) leads to the quantification of the complex at low potential, because CBNPs are capable of electrocatalitically enhancing the phosphomolybdate complex reduction at +125 mV versus Ag/AgCl without fouling problems. The developed system also incorporates reagents and waste storage and is connected to a portable potentiostat for rapid detection and quantification of phosphate. Main analytical parameters, such as working potential, reagent concentration, type of cell, and flow rate, were evaluated and optimized. This system was characterized by a low detection limit (6 µM). Interference studies were carried out. Good recovery percentages comprised between 89 and 131.5% were achieved in different water sources, highlighting its suitability for field measurements.

Printing silicone-based hydrophobic barriers on paper for microfluidic assays using low-cost ink jet printers.

Paper-based microfluidic devices exhibit many advantages for biological assays. Normally, the assays are restricted to certain areas of the paper by hydrophobic barriers comprised of wax or alkyl ketene dimers (AKD). Neither hydrophobic barrier is able to constrain aqueous solutions of surfactants, which are frequently used in biological assays. We demonstrate that rapidly curing silicone resins can be inkjet printed onto pure cellulose paper using inexpensive thermal ink-jet printers. The Piers-Rubinsztajn (PR) reaction dominates the cure chemistry leading to cellulose fibers that are surface coated with a silicone resin. The resulting barriers are able to resist penetration by surfactant solutions and even by the lower surface energy solvents DMF and DMSO. The utility of the barrier was demonstrated using a coliform assay based on detection of ß-galactosidase.

A rapid, straightforward, and print house compatible mass fabrication method for integrating 3D paper-based microfluidics.

Three-dimensional (3D) paper-based microfluidics, which is featured with high performance and speedy determination, promise to carry out multistep sample pretreatment and orderly chemical reaction, which have been used for medical diagnosis, cell culture, environment determination, and so on with broad market prospect. However, there are some drawbacks in the existing fabrication methods for 3D paper-based microfluidics, such as, cumbersome and time-consuming device assembly; expensive and difficult process for manufacture; contamination caused by organic reagents from their fabrication process. Here, we present a simple printing-bookbinding method for mass fabricating 3D paper-based microfluidics. This approach involves two main steps: (i) wax-printing, (ii) bookbinding. We tested the delivery capability, diffusion rate, homogeneity and demonstrated the applicability of the device to chemical analysis by nitrite colorimetric assays. The described method is rapid (<30 s), cheap, easy to manipulate, and compatible with the flat stitching method that is common in a print house, making itself an ideal scheme for large-scale production of 3D paper-based microfluidics.

3D printing: making things at the library.

3D printers are a new technology that creates physical objects from digital files. Uses for these printers include printing models, parts, and toys. 3D printers are also being developed for medical applications, including printed bone, skin, and even complete organs. Although medical printing lags behind other uses for 3D printing, it has the potential to radically change the practice of medicine over the next decade. Falling costs for hardware have made 3D printers an inexpensive technology that libraries can offer their patrons. Medical librarians will want to be familiar with this technology, as it is sure to have wide-reaching effects on the practice of medicine.

Low Cost and Lithography-free Stamp fabrication for Microcontact Printing.

Microcontact printing (µCP) is a commonly used technique for patterning proteins of interest on substrates. The cells take the shape of these printed patterns. This technique is used to explore the effect of cellular morphology on their various functions such as survival, differentiation, migration, etc. An essential step for µCP is to fabricate a stamp from a silicon mould, prepared using lithography. Lithography is cost intensive and needs a high level of expertise to handle the instrumentation. Also, one stamp can be used to print patterns of one size and shape. Here, to overcome these limitations, we devised a low-cost fabrication technique using readily available objects such as injection needles and polystyrene beads. We patterned the C2C12, myoblasts cells on the shapes printed using lithography-free fabricated stamps. We further exploited the surface curvature of the stamp to vary the size of the print either by changing the applied load and/or the substrate stiffness. We showed that the print dimension could be predicted well by using JKR theory of contact mechanics. Moreover, some innovative improvisations enabled us to print complex shapes, which would be otherwise difficult with conventional lithography technique. We envisage that this low cost and easy to fabricate method will allow many research laboratories with limited resources to perform exciting research which is at present out of their reach.

Low-cost printing of poly(dimethylsiloxane) barriers to define microchannels in paper.

This paper describes the use of a modified x,y-plotter to generate hydrophilic channels by printing a solution of hydrophobic polymer (pol(dimethylsiloxane; PDMS) dissolved in hexanes onto filter paper. The PDMS penetrates the depth of the paper and forms a hydrophobic wall that aqueous solutions cannot cross. The minimum size of printed features is approximately 1 mm; this resolution is adequate for the rapid prototyping of hand-held, visually read, diagnostic assays (and other microfluidic systems) based on paper. After curing the printed PDMS, the paper-based devices can be bent or folded to generate three-dimensional systems of channels. Capillary action pulls aqueous samples into the paper channels. Colorimetric assays for the presence of glucose and protein are demonstrated in the printed devices; spots of Bromothymol Blue distinguished samples with slightly basic pH (8.0) from samples with slightly acidic pH (6.5). The work also describes using printed devices that can be loaded using multipipets and printed flexible, foldable channels in paper over areas larger than 100 cm2.

Multifunctional self-assembled monolayers via microcontact printing and degas-driven flow guided patterning.

Soft lithography-based patterning techniques have been developed to investigate biological and chemical phenomena. Until now, micropatterning with various materials required multiple procedural steps such as repeating layer-by-layer patterning, aligning of stamps, and incubating printed inks. Herein, we describe a facile micropatterning method for producing chemically well-defined surface architectures by combining microcontact (µCP) and microfluidic vacuum-assisted degas-driven flow guided patterning (DFGP) with a poly(dimethylsiloxane) (PDMS) stamp. To demonstrate our concept, we fabricated a bi-composite micropatterned surface with different functional molecular inks such as fluorescein isothiocyanate labelled bovine serum albumin (FITC-BSA) and polyethylene glycol (PEG)-silane for a biomolecule array, and 3-aminopropyltriethoxysilane (APTES) and PEG-silane pattern for a self-assembled colloid gold nanoparticle monolayer. With a certain composition of molecular inks for the patterning, bi-composite surface patterns could be produced by this µCP-DFGP approach without any supplementary process. This patterning approach can be used in microfabrication and highly applicable to biomolecules and nanoparticles that spread as a monolayer.

Low-cost printing of computerised tomography (CT) images where there is no dedicated CT camera.

Many developing countries still rely on conventional hard copy images to transfer information among physicians. We have developed a low-cost alternative method of printing computerised tomography (CT) scan images where there is no dedicated camera. A digital camera is used to photograph images from the CT scan screen monitor. The images are then transferred to a PC via a USB port, before being printed on glossy paper using an inkjet printer. The method can be applied to other imaging modalities like ultrasound and MRI and appears worthy of emulation elsewhere in the developing world where resources and technical expertise are scarce.

Multilevel fluidic flow control in a rotationally-driven polyester film microdevice created using laser print, cut and laminate.

This paper presents a simple and cost-effective polyester toner microchip fabricated with laser print and cut lithography (PCL) to use with a battery-powered centrifugal platform for fluid handling. The combination of the PCL microfluidic disc and centrifugal platform: (1) allows parallel aliquoting of two different reagents of four different volumes ranging from nL to µL with an accuracy comparable to a piston-driven air pipette; (2) incorporates a reciprocating mixing unit driven by a surface-tension pump for further dilution of reagents, and (3) is amenable to larger scale integration of assay multiplexing (including all valves and mixers) without substantially increasing fabrication cost and time. For a proof of principle, a 10 min colorimetric assay for the quantitation of the protein level in the human blood plasma samples is demonstrated on chip with a limit of detection of ∼5 mg mL(-1) and coefficient of variance of ∼7%.

Low-cost, high-throughput fabrication of cloth-based microfluidic devices using a photolithographical patterning technique.

In this work, we first report a facile, low-cost and high-throughput method for photolithographical fabrication of microfluidic cloth-based analytical devices (µCADs) by simply using a cotton cloth as a substrate material and employing an inexpensive hydrophobic photoresist laboratory-formulated from commercially available reagents, which allows patterning of reproducible hydrophilic-hydrophobic features in the cloth with well-defined and uniform boundaries. Firstly, we evaluated the wicking properties of cotton cloths by testing the wicking rate in the cloth channel, in combination with scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analyses. It is demonstrated that the wicking properties of the cloth microfluidic channel can be improved by soaking the cloth substrate in 20 wt% NaOH solution and by washing the cloth-based microfluidic patterns with 3 wt% SDS solution. Next, we studied the minimum dimensions achievable for the width of the hydrophobic barriers and hydrophilic channels. The results indicate that the smallest width for a desired hydrophobic barrier is designed to be 100 µm and that for a desired hydrophilic channel is designed to be 500 µm. Finally, the high-throughput µCADs prepared using the developed fabrication technique were demonstrated for colorimetric assays of glucose and protein in artificial urine samples. It has been shown that the photolithographically patterned µCADs have potential for a simple, quantitative colorimetric urine test. The combination of cheap cloth and inexpensive high-throughput photolithography enables the development of new types of low-cost cloth-based microfluidic devices, such as "microzone plates" and "gate arrays", which provide new methods to perform biochemical assays or control fluid flow.

A Low-Cost Inkjet-Printed Glucose Test Strip System for Resource-Poor Settings.

BACKGROUND: The prevalence of diabetes is increasing in low-resource settings; however, accessing glucose monitoring is extremely difficult and expensive in these regions. Work is being done to address the multitude of issues surrounding diabetes care in low-resource settings, but an affordable glucose monitoring solution has yet to be presented. An inkjet-printed test strip solution is being proposed as a solution to this problem. METHODS: The use of a standard inkjet printer is being proposed as a manufacturing method for low-cost glucose monitoring test strips. The printer cartridges are filled with enzyme and dye solutions that are printed onto filter paper. The result is a colorimetric strip that turns a blue/green color in the presence of blood glucose. RESULTS: Using a light-based spectroscopic reading, the strips show a linear color change with an R(2) = .99 using glucose standards and an R(2) = .93 with bovine blood. Initial testing with bovine blood indicates that the strip accuracy is comparable to the International Organization for Standardization (ISO) standard 15197 for glucose testing in the 0-350 mg/dL range. However, further testing with human blood will be required to confirm this. A visible color gradient was observed with both the glucose standard and bovine blood experiment, which could be used as a visual indicator in cases where an electronic glucose meter was unavailable. CONCLUSIONS: These results indicate that an inkjet-printed filter paper test strip is a feasible method for monitoring blood glucose levels. The use of inkjet printers would allow for local manufacturing to increase supply in remote regions. This system has the potential to address the dire need for glucose monitoring in low-resource settings.

Hardcopy recording technologies for digitally formatted image data.

The hardcopy recording technologies of video cameras, slow-scan (digital spot) recorders, and laser film printers are presented and compared. Slow-scan (digital spot) recorders offer a few advantages when compared with multiformat video cameras. But only laser film printers provide the high-quality hardcopy recordings and speed required by newer digital imaging modalities.

Videophotolaryngography using a new low cost video printer. Instant electronic filmless photography.

We introduce a new concept of electronic videophotography of the larynx on the television screen using a new Mitsubishi video printer. With this method no standard film or chemical processing are used. Black and white prints of the television image can be electronically reproduced in less than 15 seconds by pressing a button on the video printer. This method is of great value for documentation of the progression of disease and comparison of the preoperative and postoperative appearances of the larynx. The printout of the black and white television image of the larynx can be attached to the patient's chart as a permanent pictorial record. Such prints can also be given to the patient or can be sent to the referring physician, the radiotherapist, and others involved in management of the patient. This method is also useful for demonstration of a pathological condition and for teaching at head and neck tumor conferences.

Non-indexed medical journals in the Web: new perspectives in the medical literature.

Many medical journals, publishing in national languages, meet serious financial problems and difficulties when they attempt to become indexed in the international indices. Obviously, this not only affects the scientific quality of non-indexed medical journals (NIMJs) but also affects the awareness of the scientific community of topics with apparently local but potentially broader scientific significance. This is a reality for over 100 Greek medical journals, none of which has a life longer than 30 years or more than 2000 subscribers. Among them, the 'Archives of Hellenic Medicine' (AHM) is published and sponsored by the Athens Medical Society (the oldest medical society in Greece founded in 1835). This peer-reviewed Journal is being published for 13 years, bimonthly, in Greek. Attempting to overcome the above mentioned problems and to be involved in the process of discovering the most effective way of scientific 'skywriting', 2 years ago, the AHM entered full-text in the Web and it was decided that up to 500% of its volume should be covered by English-language papers. As a result, the AHM are now included in the main Web lists of medical journals and their home page is linked in many academic pages having approximately 500 hits/month. Furthermore, 45 retrievals of AHM's English-language papers or English abstracts of Greek-language articles were reported by e-mail response from abroad. Considered apart from the paper-publishing, the expenses of the digital publishing of the AHM are about half of those of paper-publishing, as they were before the appearance of the Journal in the Web. Up to now, about 40% of the Journal's digital publishing cost is covered by advertisements included in its pages and by a modification of its paper-publishing policy. It is concluded that the international scientific community is not indifferent for information published in NIMJs. Medical national minorities working abroad express special interest for this type of information. The Web makes the NIMJs accessible to these potential readers, who would never have the chance to acquire them in their printed form.