Simultaneous detection of SERS and fluorescence using a single excitation for microbead-based analysis.

We demonstrate simultaneous detection of surface-enhanced Raman scattering (SERS) and fluorescence signals from a silver microbead. For the dual signal generation, silver microbeads with a diameter of 15 microm were functionalized with benzenethiol (BT) as a Raman tag and a cardiac troponin I (cTnI) antibody on their surface. SERS and fluorescence signals were obtained using a single argon laser source with 488 nm wavelength. The SERS signals from Raman tag can be used as identification indices for decoding a particular microbead, while the fluorescence signals provide the information about molecular interactions with a specific biomarker. With simultaneous detection of SERS and fluorescence signals using single excitation on the functionalized microbeads, we successfully showed the possibility of a simple barcoding strategy for multiplex analysis using suspension arrays.

Pulse push/pull hemodialysis in a canine renal failure model.

A new dialysis modality was devised to increase convective mass transfer. Blood and dialysate are circulated by a pulsatile pump, but with pulsatile flow patterns that are 180 degrees out of phase, which causes blood-to-dialysate pressure gradients to oscillate between positive and negative. In the present study, hemodialytic performance of the devised modality was investigated using a canine renal failure model. Membrane hydraulic permeabilities (K(uf)) and fiber bundle volumes (FBV) were measured after each dialysis session. Postdialysis K(uf) and FBV were then compared with those with conventional high-flux hemodialysis. No complications concerning animals or technical problems with the devised modality were encountered. Urea and creatinine reductions were satisfactory. Postdialysis K(uf) and FBV values were significantly reduced after hemodialysis sessions, but were higher for the new modality. The devised modality incorporated with blood and dialysate pulsation offers a simple but safe means new mode of hemodialysis.

Pulse push/pull hemodialysis: in vitro study on new dialysis modality with higher convective efficiency.

Midsize molecule retention is related with renal-failure-associated mortality. Here, the authors describe a new dialysis modality, pulse push/pull hemodialysis (PPPHD), which increases convective clearance. Blood and dialysate are circulated by a pulsatile pump, but with pulsatile flow patterns that are 180 degrees out of phase. This causes blood-to-dialysate pressure gradients that oscillate between positive and negative, and which cause consecutive periods of ultrafiltration and backfiltration. The devised PPPHD was compared with conventional high-flux hemodialysis (CHFHD) in terms of solute clearances, albumin loss, and total protein levels. Human plasma containing dissolved uremic marker molecules was used as a blood substitute, and clearances were investigated for blood urea nitrogen, creatinine, vitamin B12, and inulin. Observed clearances were found to be significantly higher for PPPHD by approximately 3-14% for low-molecular-weight solutes, by 47-48% for vitamin B12, and by 38-49% for inulin than for CHFHD. No albumin loss was observed in either of these two study groups. The authors conclude that PPPHD offers a simple straightforward means of enhancing uremic molecule removal by increasing total ultrafiltration volume without the need to infuse replacement fluid.

Hemodialysis using a valveless pulsatile blood pump.

Research on pulsatile blood pumps for extracorporeal life support has been widely performed because of the proven advantageous effects of blood pulsation. However, studies on the use of pulsatile blood pumps for hemodialysis are limited, although available evidence demonstrates that pulsatile blood flow has a positive influence on dialysis outcome. Therefore, the authors designed a new pulsatile pump, which is characterized by minimal-occlusion of blood-containing tubing, no requirement for valves, and no blood flow regurgitation. In-vitro hemolysis tests were conducted using fresh bovine blood, and the normalized index of hemolysis was adopted to compare blood traumas induced by the devised pulsatile pump and a conventional roller pump. In addition, experimental hemodialyses with a canine renal failure model were performed using the devised pump. Normalized index of hemolysis levels obtained was much smaller for the devised pulse pump (45 +/- 21 mg/100 L) than for the roller pump (103 +/- 10 mg/100 L), and no technical problems were encountered during dialysis sessions. Blood and dialysate flow rates were maintained at predetermined values and molecular removal was satisfactory. Postdialysis urea and creatinine reduction ratios were 61.8% +/- 10.6% and 57.4% +/- 9.0%, respectively. Pulsatile flow has usually been generated using pulsatile devices containing valves, but the valves cause concern in terms of the clinical applications of these devices. However, the described pulsatile pump does not require valves, and yet no blood flow regurgitation was observed.

Convection-enhanced high-flux hemodialysis.

Internal filtration contributes to convective clearance in high-flux hemodialysis but its contribution is limited by low pressure gradients. Therefore, a modification using a conventional dialyzer was conceived to enhance internal filtration and backfiltration (BF) rates. The modified dialyzer includes two longitudinal independent regions for blood flow, which were created by redesigning dialyzer caps. Blood pressures remained higher than dialysate pressures in one region and lower in the other region, allowing continuous internal filtration and BF in these respective regions. Modified and conventional dialyzers were compared in terms of pressure gradients and solute clearances. Thus, our experiments involved two groups: the modified dialyzer group and the conventional dialyzer group. A renal failure model was established using a dog weighing 25-30 kg by renal artery and vein ligation. With the exception of the dialyzers, experimental conditions were identical in the two groups. The pressure gradients between blood and dialysate were much higher for the modified dialyzer than for the conventional dialyzer. No significant differences were observed with respect to small solute clearances between the two groups, but mid-range solute clearances were significantly higher in the modified group. More optimization is required before the devised unit can be used clinically. However, the devised unit offers a straightforward means of regulating internal filtration and BF rates.