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1.
We reported the fabrication and characterization of nanofluidic channels by Triple Thermal Oxidation and Silicon-Glass Anodic Bonding. Planar nanochannels with depths from sub-100 nm down to sub-10 nm were realized by this method. A theoretical model was developed to precisely predict the depth of nanochannels. The depth and uniformity of nanochannels showed good stability during anodic bonding. This method is promising for various nanofluidic studies, such as nanofluidic electrokinetics, biomolecule manipulation, and energy conversion.  相似文献   

2.
An easy method is introduced allowing fast polydimethylsiloxane (PDMS) replication of nanofluidic lab-on-chip devices using accurately fabricated molds featuring cross-sections down to 60 nm. A high quality master is obtained through proton beam writing and UV lithography. This master can be used more than 200 times to replicate nanofluidic devices capable of handling single DNA molecules. This method allows to fabricate nanofluidic devices through simple PDMS casting. The extensions of YOYO-1 stained bacteriophage T4 and λ−DNA inside these nanochannels have been investigated using fluorescence microscopy and follow the scaling prediction of a large, locally coiled polymer chain confined in nanochannels.  相似文献   

3.
For the first time, we report on the preliminary evaluation of gold coated optical fibers (GCOFs) as three-dimensional (3D) electrodes for a membraneless glucose/O2 enzymatic biofuel cell. Two off-the-shelf 125 μm diameter GCOFs were integrated into a 3D microfluidic chip fabricated via rapid prototyping. Using soluble enzymes and a 10 mM glucose solution flowing at an average velocity of 16 mm s−1 along 3 mm long GCOFs, the maximum power density reached 30.0 ± 0.1 μW cm−2 at a current density of 160.6 ± 0.3 μA cm−2. Bundles composed of multiple GCOFs could further enhance these first results while serving as substrates for enzyme immobilization.  相似文献   

4.
A technique for microfluidic, pH modulated DNA capture and purification using chitosan functionalized glycidyl methacrylate monoliths is presented. Highly porous polymer monoliths are formed and subsequently functionalized off-chip in a batch process before insertion into thermoplastic microchannels prior to solvent bonding, simplifying the overall fabrication process by eliminating the need for on-chip surface modifications. The monolith anchoring method allows for the use of large cross-section monoliths enabling high flowrates and high DNA capture capacity with a minimum of added design complexity. Using monolith capture elements requiring less than 1 mm2 of chip surface area, loading levels above 100 ng are demonstrated, with DNA capture and elution efficiency of 54.2% ± 14.2% achieved.  相似文献   

5.
Isolation and enumeration of circulating tumor cells (CTCs) are used to monitor metastatic disease progression and guide cancer therapy. However, currently available technologies are limited to cells expressing specific cell surface markers, such as epithelial cell adhesion molecule (EpCAM) or have limited specificity because they are based on cell size alone. We developed a device, ApoStream™ that overcomes these limitations by exploiting differences in the biophysical characteristics between cancer cells and normal, healthy blood cells to capture CTCs using dielectrophoretic technology in a microfluidic flow chamber. Further, the system overcomes throughput limitations by operating in continuous mode for efficient isolation and enrichment of CTCs from blood. The performance of the device was optimized using a design of experiment approach for key operating parameters such as frequency, voltage and flow rates, and buffer formulations. Cell spiking studies were conducted using SKOV3 or MDA-MB-231 cell lines that have a high and low expression level of EpCAM, respectively, to demonstrate linearity and precision of recovery independent of EpCAM receptor levels. The average recovery of SKOV3 and MDA-MB-231 cancer cells spiked into approximately 12 × 106 peripheral blood mononuclear cells obtained from 7.5 ml normal human donor blood was 75.4% ± 3.1% (n = 12) and 71.2% ± 1.6% (n = 6), respectively. The intra-day and inter-day precision coefficients of variation of the device were both less than 3%. Linear regression analysis yielded a correlation coefficient (R2) of more than 0.99 for a spiking range of 4–2600 cells. The viability of MDA-MB-231 cancer cells captured with ApoStream was greater than 97.1% and there was no difference in cell growth up to 7 days in culture compared to controls. The ApoStream device demonstrated high precision and linearity of recovery of viable cancer cells independent of their EpCAM expression level. Isolation and enrichment of viable cancer cells from ApoStream enables molecular characterization of CTCs from a wide range of cancer types.  相似文献   

6.
Thanks to its unique features at the nanoscale, nanofluidics, the study and application of fluid flow in nanochannels/nanopores with at least one characteristic size smaller than 100 nm, has enabled the occurrence of many interesting transport phenomena and has shown great potential in both bio- and energy-related fields. The unprecedented growth of this research field is apparently attributed to the rapid development of micro/nanofabrication techniques. In this review, we summarize recent activities and achievements of nanofabrication for nanofluidic devices, especially those reported in the past four years. Three major nanofabrication strategies, including nanolithography, microelectromechanical system based techniques, and methods using various nanomaterials, are introduced with specific fabrication approaches. Other unconventional fabrication attempts which utilize special polymer properties, various microfabrication failure mechanisms, and macro/microscale machining techniques are also presented. Based on these fabrication techniques, an inclusive guideline for materials and processes selection in the preparation of nanofluidic devices is provided. Finally, technical challenges along with possible opportunities in the present nanofabrication for nanofluidic study are discussed.  相似文献   

7.
Some aqueous reactions in biological or chemical fields are accomplished at a high temperature. When the reaction temperature is higher than 100 °C, an autoclave reactor is usually required to elevate the boiling point of the water by creating a high-pressure environment in a closed system. This work presented an alternative continuous flowing microfluidic solution for aqueous reaction with a reaction temperature higher than 100 °C. The pressure regulating function was successfully fulfilled by a small microchannel based on a delicate hydrodynamic design. Combined with micro heater and temperature sensor that integrated in a single chip by utilizing silicon-based microfabrication techniques, this pressure regulating microchannel generated a high-pressure/high-temperature environment in the upstream reaction zone when the reagents continuously flow through the chip. As a preliminary demonstration, thermal digestion of aqueous total phosphorus sample was achieved in this continuous flowing micro-reactor at a working pressure of 990 kPa (under the working flow rate of 20 nl/s) along with a reaction temperature of 145 °C. This continuous flowing microfluidic solution for high-temperature reaction may find applications in various micro total analysis systems.  相似文献   

8.
Activated carbon fabrics (ACF) mask prevents the absorption of lead and reduce its adverse effects of human health. Aim of this study to know the blood lead level and its effects on heme biosynthesis and hematological parameters after using 2 months activated carbon fabric mask of battery manufacturing workers (BMW). Blood lead level, heme biosynthesis and hematological parameters were measured by using standard method. Blood lead level (P < 0.001, − 13.5%) was significantly decreased, activated δ-aminolevulinic acid dehydratase (P < 0.001, 11.97%) and non-activated δ- aminolevulinic acid dehydratase (P < 0.001, 23.17%) enzyme activity were significantly increased, however, the ratio of activated to Non-activated δ- ALAD (P < 0.001, − 10.13%) was significantly decreased, urinary excretion of δ- aminolevulinic acid (P < 0.001, − 10.49%) and porphobilinogen (P < 0.001, − 7.38%) were significantly decreased after using 2 months ACF mask as compared to before using mask of BMW. Hematological parameters i.e Hb (P < 0.05, 13.42%), PCV (P < 0.05, 7.23%), MCV (P < 0.05, 1.9%) were significantly increased and total WBC count (P < 0.05, − 5.18%) was significantly decreased after using 2 months ACF mask as compared to before using mask of BMW. Two months using ACF mask reduces the blood lead level and improves the δ-ALDH activity and hematological parameters, decreases the urinary excretion of δ-ALA, PBG of battery manufacturing workers. Therefore, the regular using of ACF mask is beneficial to prevent the lead absorption and its adverse effects on human health.  相似文献   

9.
A relatively simple, inexpensive and reliable technique was developed to fabricate an array of nanochannels. Moreover, the nanochannels are directly integrated to microchannels as a whole, which facilitates solution loading from the millimeter-scaled loading reservoirs into the nanochannels. It is found that continuous bovine serum albumin (BSA) line structures with triangle-like cross section at nanoscale can be obtained by evaporation of BSA solution with concentration between 0.5 wt. % and 1 wt. % inside the microchannels. The poly(dimethyl siloxane) nanochannels were replicated from these line structures, followed by sealing with the glass slide. The DNA molecules can be stretched inside the nanochannels as fabricated.  相似文献   

10.
We have developed a two-step electron-beam lithography process to fabricate a tandem array of three pairs of tip-like gold nanoelectronic detectors with electrode gap size as small as 9 nm, embedded in a coplanar fashion to 60 nm deep, 100 nm wide, and up to 150 μm long nanochannels coupled to a world-micro-nanofluidic interface for easy sample introduction. Experimental tests with a sealed device using DNA-protein complexes demonstrate the coplanarity of the nanoelectrodes to the nanochannel surface. Further, this device could improve transverse current detection by correlated time-of-flight measurements of translocating samples, and serve as an autocalibrated velocimeter and nanoscale tandem Coulter counters for single molecule analysis of heterogeneous samples.  相似文献   

11.
Deterministic lateral displacement (DLD) is a microfluidic size-based particle separation or filter technology with applications in cell separation and enrichment. Currently, there are no cost-effective manufacturing methods for this promising microfluidic technology. In this fabrication paper, however, we develop a simple, yet robust protocol for thermoplastic DLD devices using regulatory-approved materials and biocompatible methods. The final standalone device allowed for volumetric flow rates of 660 μl min−1 while reducing the manufacturing time to <1 h. Optical profilometry and image analysis were employed to assess manufacturing accuracy and precision; the average replicated post height was 0.48% less than the average post height on the master mold and the average replicated array pitch was 1.1% less than the original design with replicated posts heights of 62.1 ± 5.1 μm (mean ± 6 standard deviations) and replicated array pitches of 35.6 ± 0.31 μm.  相似文献   

12.
Despite ample sunshine, 50–90% Indian children have Vitamin D deficiency (VDD). This enigma of widespread VDD needs exploration especially among under-fives as physiological variations in Vitamin D Binding Protein (VDBP) levels could be potential confounders in the interpretation of total 25-hydroxyvitamin D [25(OH)D]. However, there is scarce information about relevance of VDBP levels in under-five age group. We therefore, explored association of VDBP levels among 1–5 year old children with VDD. Serum levels of 25(OH)D, VDBP, calcium, parathyroid hormone (PTH) and alkaline phosphatase were estimated in 210 apparently healthy children in the age group of 1–5 years. VDD was defined as serum 25(OH)D levels < 20 ng/ml as per the IOM classification. VDBP levels were classified as low if levels were < 168 μg/ml as per the kit. The prevalence of VDD was 79.5% (n = 167) and VDBP levels were low in 48.6% (n = 102) of children. 25(OH)D levels correlated positively with VDBP (r = 0.298, p = 0.0001). A significant number of children (52.7%) with VDD had low VDBP (p = 0.015). and despite adequate sun exposure, 43% of children showed VDD and 56.6% had low VDPB levels. The low VDBP levels largely explain low 25OHD levels without necessarily implying VDD. It may add a new dimension for better understanding of widespread VDD among under-five children. It thus, points towards the need for redefining cut offs and complete evaluation of vitamin D status among under-fives including VDBP.  相似文献   

13.
Essential hypertension (EH) is a multifactorial and complex disease with high rate of incidence and associated co-morbidities. Previous studies do not provide unanimous results for the risk of hypertension and association with Fok I genotype frequency and serum vitamin D levels. Hence, this study was undertaken to determine the status of Fok I vitamin D receptor (VDR) gene polymorphism along with vitamin D levels and blood pressure in patients with EH. Four hundred (200 controls and 200 cases of essential hypertension) participants from general Indian population were enrolled in this study. Peripheral blood samples were collected for genotyping Fok I-VDR gene polymorphism using PCR–RFLP method whereas 25-OH vitamin D levels in serum were quantified using high performance liquid chromatography (HPLC). Significantly reduced 25-OH vitamin D levels were observed in patients with EH (24.04 ± 8.62 vs 50.46 ± 15.46) compared to control subjects (p = 0.0001). Homozygous recessive genotype ‘ff’ frequency was increased by 8.06 fold (CI: 3.71–17.47, p = 0.0001) in patients with EH compared to dominant ‘FF’ genotype frequency. In conclusion, recessive ‘ff’ genotype frequency correlates with reduced serum vitamin D levels and results in significantly increased systolic and diastolic blood pressures leading to predisposition of EH.  相似文献   

14.
While advances in genomics have enabled sensitive and highly parallel detection of nucleic acid targets, the isolation and extraction of the nucleic acids remain a critical bottleneck in the workflow. We present here a simple 3D printed microfluidic chip that allows for the vortex and centrifugation free extraction of nucleic acids. This novel microfluidic chip utilizes the presence of a water and oil interface to filter out the lysate contaminants. The pure nucleic acids, while bound on cellulose particles, are magnetically moved across the oil layer. We demonstrated efficient and rapid extraction of spiked Human Papillomavirus (HPV) 18 plasmids in specimen transport medium, in under 15 min. An overall extraction efficiency of 61% is observed across a range of HPV plasmid concentrations (5 × 101 to 5 × 106 copies/100 μl). The magnetic, interfacial, and viscous drag forces inside the microgeometries of the chip are modeled. We have also developed a kinetics model for the adsorption of nucleic acids on cellulose functionalized superparamagnetic beads. We also clarify here the role of carrier nucleic acids in the adsorption and isolation of nucleic acids. Based on the various mechanistic insights detailed here, customized microfluidic devices can be designed to meet the range of current and emerging point of care diagnostics needs.  相似文献   

15.
Nowadays, microfluidics is attracting more and more attentions in the biological society and has provided powerful solutions for various applications. This paper reported a microfluidic strategy for aqueous sample sterilization. A well-designed small microchannel with a high hydrodynamic resistance was used to function as an in-chip pressure regulator. The pressure in the upstream microchannel was thereby elevated which made it possible to maintain a boiling-free high temperature environment for aqueous sample sterilization. A 120 °C temperature along with a pressure of 400 kPa was successfully achieved inside the chip to sterilize aqueous samples with E. coli and Staphylococcus aureus inside. This technique will find wide applications in portable cell culturing, microsurgery in wild fields, and other related micro total analysis systems.Microfluidics, which confines fluid flow at microscale, attracts more and more attentions in the biological society.1–4 By scaling the flow domain down to microliter level, microfluidics shows attractive merits of low sample consumption, precise biological objective manipulation, and fast momentum/energy transportation. For example, various cell operations, such as culturing5–7 and sorting,8–10 have already been demonstrated with microfluidic approaches. In most biological applications, sterilization is a key sample pre-treatment step to avoid contamination. However, as far as the author knew, this important pre-treatment operation is generally achieved in an off-chip way, by using high temperature and high pressure autoclave. Actually, microfluidics has already been utilized to develop new solution for high pressure/temperature reactions. The required high pressure/temperature condition was generated either by combining off-chip back pressure regulator and hot-oil bath,11,12 or by integrating pressure regulator, heater, and temperature sensor into a single chip.13 This work presented a microfluidic sterilization strategy by implementing the previously developed continuous flowing high pressure/temperature microfluidic reactor.Figure ​Figure11 shows the working principle of the present microfluidic sterilization chip. The chip consists of three zones: sample loading (a microchannel with length of 270 mm and width of 40 μm), sterilization (length of 216 mm and width of 100 μm), and pressure regulating (length of 42 mm and width of 5 μm). Three functional zones were separated by two thermal isolation trenches. The sample was injected into the chip by a syringe pump and experienced two-step filtrations (feature sizes of 20 μm and 5 μm, not shown in Figure ​Figure1)1) at the entrance to avoid the channel clog. All channels had the same depth of 40 μm. According to the Hagen–Poiseuille relationship,15 the pressure regulating channel had a large flow resistance (around 1.09 × 1017 Pa·s/m3, see supplementary S1 for details16) because of its small width, thereby generated a high working pressure in the upstream sterilization channel under a given flow rate. The boiling point of the solution will then be raised up by the elevated pressure in the sterilization zone followed by the Antoine equation.16 By integrating heater/temperature sensors in the pressurized zone, a high temperature environment with temperature higher than 100 °C can thereby be realized for aqueous sample sterilization. The sample was collected from the outlet and cultured at 37 °C for 12 h. Bacterial colony was counted to evaluate the sterilization performance.Open in a separate windowFIG. 1.Working principle of the present microfluidic sterilization. Only microfluidic channel, heater, and temperature sensor were schematically shown. The varied colour of the microchannel represents the pressure and that of the halation stands for the temperature.Fabrication of this chip has been introduced elsewhere.14 The fabricated chip and the experimental system are shown in Figure ​Figure2.2. There were two inlets of the chip. While, in the experiment, only one inlet used and connected to the syringe pump. The backup one was blocked manually. The sample load zone was arranged in between of the sterilization zone and the pressure regulating zone based on thermal management consideration. A temperature control system (heater/temperature sensor, power source, and multi-meter) was setup to provide the required high temperature. The heater and the temperature sensor were microfabricated Pt resistors. The temperature coefficient of resistance (TCR) was measured as 0.00152 K−1.Open in a separate windowFIG. 2.The fabricated chip and the experimental system. (a) Two chips with a penny for comparison. The left chip was viewed from the heater/temperature sensor side, while the right one was observed from the microchannel side (through a glass substrate). (b) The experimental system.Thermal isolation performance of the present chip before packaging with inlet/outlet was shown in Figure ​Figure3,3, to show the thermal interference issue. The results indicated that when the sterilization zone was heated up to 140 °C, the pressure regulating zone was about 40 °C. At this temperature, the viscosity of water decreases to 0.653 mPa·s from 1.00 mPa·s (at 20 °C), which will make the pressure in the sterilization zone reduced from 539 kPa (calculated at 20 °C and flow rate of 4 nl/s) to 387 kPa. The boiling point will then decrease to 142.8 °C, which will guarantee a boiling-free sterilization. In the cases without the thermal isolation trenches, the temperature of the pressure regulating zone reached as high as 75 °C because of the thermal interference from the sterilization zone, as shown in Figure ​Figure3.3. The pressure in the sterilization zone was then reduced to 268 kPa (calculated at flow rate of 4 nl/s) and the boiling temperature was around 130 °C, which was lower than the set sterilization temperature. Detail calculation can be found in supplementary S2.16Open in a separate windowFIG. 3.The temperature distribution of the chips (before packaged) with and without thermal isolation trenches (powered at 1 W). The data were extracted from the central lines of infrared images, as shown as inserts.Bacterial sterilization performance of the present chip was tested and the experimental results were shown in Figure ​Figure4.4. E. coli with initial concentration of 106/ml was pumped into and flew through the chip with the sterilization temperatures varied from 25 °C to 120 °C at flow rates of 2 nl/s and 4 nl/s. The outflow was collected and inoculated onto the SS agar plate evenly with inoculation loops. The population of bacteria in the outflow was counted based on the bacterial colonies after incubation at 37 °C for 12 h. Typical bacterial colonies were shown in Figure ​Figure4.4. The low flow rate case showed a better sterilization performance because of the longer staying period in the sterilization channel. The population of E. coli was around 1.25 × 104/ml after a 432 s-long, 70 °C sterilization (at flow rate of 2 nl/s). While at the flow rate of 4 nl/s, the cultivation result indicated the population was around 3.8 × 104/ml because the sterilization time was shorten to 216 s. A control case, where the solution flew through an un-heated chip at 2 nl/s, was conducted to investigate the effect of the shear stress on the sterilization performance (see the supplementary S3 for details16). As listed in Table ​TableI,I, the results indicated that the shear stress did not show any noticeable effect on the bacterial sterilization. When the chip was not heated, i.e., the case with the largest shear stress because of the highest viscosity of fluid, the bacterial cultivation was nearly the same as the off-chip results (no stress). The temperature has the most significant effect on the sterilization performance. No noticeable bacteria proliferation was observed in the cases with the sterilization temperature higher than 100 °C, as shown in Figure ​Figure44.

Table I.

The E. coli cultivation results under different flow rates and sterilization temperatures. a
 25 °C70 °C100 °C120 °C25 °C b
2 nl/s1.89/+++1.38/+1.16/−1.04/−0/+++
4 nl/s3.78/+++2.76/+2.32/−2.08/−0/+++
Open in a separate windowaData in the table are shear stress (Pa)/population of bacteria, where “+++” indicates a large proliferation, “+” means small but noticeable proliferation, “−” represents no proliferation.bOff-chip control group.Open in a separate windowFIG. 4.Sterilization performance of the present chip with E. coli and S. aureus as test bacteria. All the original population was 106/ml. Inserted images showed the images of the culture disk after bacteria incubation.Sterilization of another commonly encountered bacterium, Staphylococcus aureus, with initial population of 106/ml was also tested in the present chip, as shown in Figure ​Figure4.4. Similarly, no noticeable S. aureus proliferation was found when the sterilization temperature was higher than 100 °C.In short, we demonstrated a microfluidic sterilization strategy by utilizing a continuous flowing high temperature/pressure chip. The population of E. coli or S. aureus was reduced from 106/ml to an undetectable level when the sterilization temperature of the chip was higher than 100 °C. The chip holds promising potential in developing portable microsystem for biological/clinical applications.  相似文献   

16.
Affinity reagents recognizing biomarkers specifically are essential components of clinical diagnostics and target therapeutics. However, conventional methods for screening of these reagents often have drawbacks such as large reagent consumption, the labor-intensive or time-consuming procedures, and the involvement of bulky or expensive equipment. Alternatively, microfluidic platforms could potentially automate the screening process within a shorter period of time and reduce reagent and sample consumption dramatically. It has been demonstrated recently that a subpopulation of tumor cells known as cancer stem cells possess high drug resistance and proliferation potential and are regarded as the main cause of metastasis. Therefore, a peptide that recognizes cancer stem cells and differentiates them from other cancer cells will be extremely useful in early diagnosis and target therapy. This study utilized M13 phage display technology to identify peptides that bind, respectively, to colon cancer cells and colon cancer stem cells using an integrated microfluidic system. In addition to positive selection, a negative selection process was integrated on the chip to achieve the selection of peptides of high affinity and specificity. We successfully screened three peptides specific to colon cancer cells and colon cancer stem cells, namely, HOLC-1, HOLC-2, and COLC-1, respectively, and their specificity was measured by the capture rate between target, control, and other cell lines. The capture rates are 43.40 ± 7.23%, 45.16 ± 7.12%, and 49.79 ± 5.34% for colon cancer cells and colon cancer stem cells, respectively, showing a higher specificity on target cells than on control and other cell lines. The developed technique may be promising for early diagnosis of cancer cells and target therapeutics.  相似文献   

17.
Solvent-induced nanocrack formation on polystyrene surface is investigated experimentally. Solubility parameter and diffusion coefficient of alcohols are employed to elucidate the swelling and cracking processes as well as the crack size. Experimental results show that the crack size increases with the heating temperature, heating time, and the concentration and volume of the alcohols. A guideline on fabricating single smaller nanocracks on polymers by solvent-induced method is provided. Nanocracks of approximately 64 nm in width and 17.4 nm in depth were created and replicated onto PDMS (polydimethylsiloxane) slabs to form nanochannels.  相似文献   

18.
Ovarian cancer has been emerged as a most common and lethal gynecological malignancy in India. High serum insulin and low adiponectin have been associated with increased risk of ovarian cancer. But their role in development of ovarian cancer is conflicting and little evidence is available. We aimed to evaluate blood levels of insulin and adiponectin in epithelial ovarian cancer (EOC) patients and their association with the risk to develop EOC. The study included following three groups; Group 1: fifty cases of cytohistopathologically confirmed cases of EOC, Group 2: fifty age matched cases of benign ovarian conditions and Group 3: fifty ages matched healthy controls with no evidence of any benign or malignant ovarian pathology as ruled out by clinical examination and relevant investigations. Cytohistopathologically confirmed and newly diagnosed cases of EOC and benign ovarian cancer were included in this study. The median value of fasting serum insulin was significantly high (15.0 µlU/ml, P = 0.02) and adiponectin were significantly low (5.1 µg/ml, P < 0.001) in ovarian cancer patients compared to benign ovarian tumors and healthy controls group. A significant increase risk of ovarian cancer was found in high tertile (≥ 18.7 µlU/ml) of serum insulin level (OR = 2.7; 95% CI = 1.00–6.67, P = 0.04) and lower tertile (≤ 5.45 µg/ml) of adiponectin level (OR = 3.2; 95% CI = 1.10–9.71, P = 0.03). High serum insulin level and low adiponectin levels were significantly associated with increased risk for development of ovarian cancer.  相似文献   

19.
Nanofluidics has a unique property that ionic conductance across a nanometer-sized confined space is strongly affected by the space surface charge density, which can be utilized to construct electrical read-out biosensor. Based on this principle, this work demonstrated a novel protein sensor along with a sandwich signal enhancement approach. Nanoparticles with designed aptamer onside are assembled in a suspended micropore to form a 3-dimensional network of nanometer-sized interstices, named as nanofluidic crystal hereafter, as the basic sensing unit. Proteins captured by aptamers will change the surface charge density of nanoparticles and thereby can be detected by monitoring the ionic conductance across this nanofluidic crystal. Another aptamer can further enlarge the variations of the surface charge density by forming a sandwich structure (capturing aptamer/protein/signal enhancement aptamer) and the read-out conductance as well. The preliminary experimental results indicated that human α-thrombin was successfully detected by the corresponding aptamer modified nanofluidic crystal with the limit of detection of 5 nM (0.18 μg/ml) and the read-out signal was enhanced up to 3 folds by using another thrombin aptamer. Being easy to graft probe, facile and low-cost to prepare the nano-device, and having an electrical read-out, the present nanofluidic crystal scheme is a promising and universal strategy for protein sensing.  相似文献   

20.
Blood analysis plays a major role in medical and science applications and white blood cells (WBCs) are an important target of analysis. We proposed an integrated microfluidic chip for direct and rapid trapping WBCs from whole blood. The microfluidic chip consists of two basic functional units: a winding channel to mix and arrays of two-layer trapping structures to trap WBCs. Red blood cells (RBCs) were eliminated through moving the winding channel and then WBCs were trapped by the arrays of trapping structures. We fabricated the PDMS (polydimethylsiloxane) chip using soft lithography and determined the critical flow velocities of tartrazine and brilliant blue water mixing and whole blood and red blood cell lysis buffer mixing in the winding channel. They are 0.25 μl/min and 0.05 μl/min, respectively. The critical flow velocity of the whole blood and red blood cell lysis buffer is lower due to larger volume of the RBCs and higher kinematic viscosity of the whole blood. The time taken for complete lysis of whole blood was about 85 s under the flow velocity 0.05 μl/min. The RBCs were lysed completely by mixing and the WBCs were trapped by the trapping structures. The chip trapped about 2.0 × 103 from 3.3 × 103 WBCs.  相似文献   

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