A Retrospective Comparison of Union Rates After Open Wedge High Tibial Osteotomies With and Without Synthetic Bone Grafts (Hydroxyapatite and ß-tricalciumphosphate) at 2 Years.

PURPOSE: To evaluate the clinical and radiological results of no bone graft (NBG) after opening wedge high tibial osteotomy (OWHTO) with a locking plate and to compare the bone union rate between the synthetic bone graft (SBG) group and the NBG group after OWHTO using serial radiographs. METHODS: From 2012 to 2015, OWHTOs were performed with SBG or without bone graft using long locking plates. Inclusion criteria were: (1) OWHTO for disease of the medial compartment with varus deformity, and (2) minimum 2-year follow-up and radiographs taken serially to 2 years. Exclusion criteria were: (1) follow-up period <2 years (n = 8) or (2) absence of at least 1 radiograph taken at each follow-up point (n = 14). We retrospectively reviewed radiographs taken preoperatively and at 6 weeks, 3 months, 6 months, 1 year, and 2 years postoperatively. Groups comprised those filled with a synthetic bone [hydroxyapatite (HA) and ß-tricalciumphosphate (TCP), n=33, SBG group] or without a bone graft (n = 38, NBG group). We compared bone union rate between the 2 groups by measuring the union zone from zone 1 to zone 5 in serial radiographs using Fisher's exact test. RESULTS: OWHTO was performed in a total of 93 knees and 71 knees were included in this study. Both groups showed good clinical and radiological results without correction loss at 2 years. The entire NBG group and 93.9% of the SBG group showed union over zone 3 at 2 years. However, the NBG group showed significantly more incorporation than the SBG group at 6 months (P = .006), 1 year (P = .0003), and 2 years (P = .0003). CONCLUSIONS: Union without correction loss was obtained after OWHTO without bone graft. The NBG group showed significantly more incorporation than the SBG group (HA and ß-TCP) within 2 years. LEVEL OF EVIDENCE: Level IV, case series.

Characterizing microscale aluminum composite layer properties on silicon solar cells with hybrid 3D scanning force measurements.

This article presents a novel technique to estimate the mechanical properties of the aluminum composite layer on silicon solar cells by using a hybrid 3-dimensional laser scanning force measurement (3-D LSFM) system. The 3-D LSFM system measures the material properties of sub-layers constituting a solar cell. This measurement is critical for realizing high-efficient ultra-thin solar cells. The screen-printed aluminum layer, which significantly affects the bowing phenomenon, is separated from the complete solar cell by removing the silicon (Si) layer with deep reactive ion etching. An elastic modulus of ~15.1 GPa and a yield strength of ~35.0 MPa for the aluminum (Al) composite layer were obtained by the 3-D LSFM system. In experiments performed for 6-inch Si solar cells, the bowing distances decreased from 12.02 to 1.18 mm while the Si layer thicknesses increased from 90 to 190 µm. These results are in excellent agreement with the theoretical predictions for ultra-thin Si thickness (90 µm) based on the obtained Al composite layer properties.

Recent advancements in optofluidics-based single-cell analysis: optical on-chip cellular manipulation, treatment, and property detection.

Cellular analysis plays important roles in various biological applications, such as cell biology, drug development, and disease diagnosis. Conventional cellular analysis usually measures the average response from a whole cell group. However, bulk measurements may cause misleading interpretations due to cell heterogeneity. Another problem is that current cellular analysis may not be able to differentiate various subsets of cell populations, each exhibiting a different behavior than the others. Single-cell analysis techniques are developed to analyze cellular properties, conditions, or functional responses in a large cell population at the individual cell level. Integrating optics with microfluidic platforms provides a well-controlled microenvironment to precisely control single cell conditions and perform non-invasive high-throughput analysis. This paper reviews recent developments in optofluidic technologies for various optics-based single-cell analyses, which involve single cell manipulation, treatment, and property detection. Finally, we provide our views on the future development of integrated optics with microfluidics for single-cell analysis and discuss potential challenges and opportunities of this emerging research field in biological applications.

Integrated nanoplasmonic sensing for cellular functional immunoanalysis using human blood.

Localized surface plasmon resonance (LSPR) nanoplasmonic effects allow for label-free, real-time detection of biomolecule binding events on a nanostructured metallic surface with simple optics and sensing tunability. Despite numerous reports on LSPR bionanosensing in the past, no study thus far has applied the technique for a cytokine secretion assay using clinically relevant immune cells from human blood. Cytokine secretion assays, a technique to quantify intercellular-signaling proteins secreted by blood immune cells, allow determination of the functional response of the donor's immune cells, thus providing valuable information about the immune status of the donor. However, implementation of LSPR bionanosensing in cellular functional immunoanalysis based on a cytokine secretion assay poses major challenges primarily owing to its limited sensitivity and a lack of sufficient sample handling capability. In this paper, we have developed a label-free LSPR biosensing technique to detect cell-secreted tumor necrosis factor (TNF)-α cytokines in clinical blood samples. Our approach integrates LSPR bionanosensors in an optofluidic platform that permits trapping and stimulation of target immune cells in a microfluidic chamber with optical access for subsequent cytokine detection. The on-chip spatial confinement of the cells is the key to rapidly increasing a cytokine concentration high enough for detection by the LSPR setup, thereby allowing the assay time and sample volume to be significantly reduced. We have successfully applied this approach first to THP-1 cells and then later to CD45 cells isolated directly from human blood. Our LSPR optofluidics device allows for detection of TNF-α secreted from cells as few as 1000, which translates into a nearly 100 times decrease in sample volume than conventional cytokine secretion assay techniques require. We achieved cellular functional immunoanalysis with a minimal blood sample volume (3 µL) and a total assay time 3 times shorter than that of the conventional enzyme-linked immunosorbent assay (ELISA).

Smart three-dimensional gas chromatography.

We developed a complete computer-controlled smart 3-dimensional gas chromatography (3-D GC) system with an automation algorithm. This smart 3-D GC architecture enabled independent optimization of and control over each dimension of separation and allowed for much longer separation time for the second- and third-dimensional columns than the conventional comprehensive 3-D GC could normally achieve. Therefore, it can potentially be employed to construct a novel GC system that exploits the multidimensional separation capability to a greater extent. In this Article, we introduced the smart 3-D GC concept, described its operation, and demonstrated its feasibility by separating 22 vapor analytes.

Smart multi-channel two-dimensional micro-gas chromatography for rapid workplace hazardous volatile organic compounds measurement.

We developed a novel smart multi-channel two-dimensional (2-D) micro-gas chromatography (µGC) architecture that shows promise to significantly improve 2-D µGC performance. In the smart µGC design, a non-destructive on-column gas detector and a flow routing system are installed between the first dimensional separation column and multiple second dimensional separation columns. The effluent from the first dimensional column is monitored in real-time and decision is then made to route the effluent to one of the second dimensional columns for further separation. As compared to the conventional 2-D µGC, the greatest benefit of the smart multi-channel 2-D µGC architecture is the enhanced separation capability of the second dimensional column and hence the overall 2-D GC performance. All the second dimensional columns are independent of each other, and their coating, length, flow rate and temperature can be customized for best separation results. In particular, there is no more constraint on the upper limit of the second dimensional column length and separation time in our architecture. Such flexibility is critical when long second dimensional separation is needed for optimal gas analysis. In addition, the smart µGC is advantageous in terms of elimination of the power intensive thermal modulator, higher peak amplitude enhancement, simplified 2-D chromatogram re-construction and potential scalability to higher dimensional separation. In this paper, we first constructed a complete smart 1 × 2 channel 2-D µGC system, along with an algorithm for automated control/operation of the system. We then characterized and optimized this µGC system, and finally employed it in two important applications that highlight its uniqueness and advantages, i.e., analysis of 31 workplace hazardous volatile organic compounds, and rapid detection and identification of target gas analytes from interference background.

Fabry-Pérot cavity sensor-based optofluidic gas chromatography using a microfabricated passive preconcentrator/injector.

This study reports on dual on-column Fabry-Pérot (FP) cavity sensor-based gas chromatography (GC) of mixtures of volatile organic compounds (VOCs) utilizing an on-chip device, the so called "microfabricated passive preconcentrator/injector (µPPI)". Comprehensive analysis of the sampling, desorption/injection, and compound separation performance of the µPPI-based optofluidic GC system is described. Here, the combined use of the µPPI and on-column FP cavity sensors in a common GC platform enabled diffusion-based passive sampling, rapid (<7 min) chromatographic separation, and optical detection for the quaternary VOC mixtures of benzene, TCE, toluene, and m-xylene at sub-ppm concentrations with a simpler fluidic setup than conventional GC systems. The FP cavity sensor arrangement provided the means to study the dynamics of the thermal desorption/injection of VOCs by the µPPI and its effect on the GC separation resolution. Our analysis of obtained chromatograms revealed a presence of the competitive adsorptions of VOC mixtures onto the adsorption sites of trapping materials in the µPPI, which decreased the effective sampling rate by ~50% for compounds with high volatility. The validated performance of the optofluidic GC system promises future development of a field deployable GC microsystem incorporating the µPPI and the FP cavity sensors.

Effect of thermal desorption kinetics on vapor injection peak irregularities by a microscale gas chromatography preconcentrator.

Microscale gas chromatography (µGC) is an emerging analytical technique for in situ analysis and on-site monitoring of volatile organic compounds (VOCs) in moderately complex mixtures. One of the critical subcomponents in a µGC system is a microfabricated preconcentrator (µ-preconcentrator), which enables detection of compounds existing in indoor/ambient air at low (~sub ppb) concentrations by enhancing their signals. The prevailing notion is that elution peak broadening and tailing phenomena resulting from undesirable conditions of a microfabricated separation column (µ-column) are the primary sources of poor chromatographic resolution. However, previous experimental results indicate that the resolution degradation still remains observed for a µ-column integrated with other µGC subcomponents even after setting optimal separation conditions. In this work, we obtain the evidence that the unoptimized µ-preconcentrator vapor release/injection performance significantly contributes to decrease the fidelity of µGC analysis using our state-of-the-art passive preconcentrator microdevice. The vapor release/injection performance is highly affected by the kinetics of the thermal desorption of compounds trapped in the microdevice. Decreasing the heating rate by 20% from the optimal rate of 90 °Cs(-1) causes a 340% increase in peak tailing as well as 70% peak broadening (30% peak height reduction) to the microscale vapor injection process.

Microfabricated passive vapor preconcentrator/injector designed for microscale gas chromatography.

The design, fabrication, and preliminary testing of a micromachined-Si passive vapor preconcentrator/injector (µPPI) are described. Intended for incorporation in a gas chromatographic microsystem (µGC) for analyzing organic vapor mixtures, the µPPI captures vapors from the air at a known rate by means of passive diffusion (i.e., without pumping) and then desorbs the vapor sample thermally by means of an integrated heater and injects it downstream (with pumping). The µPPI chip comprises a 1.8 µL deep reactive-ion-etched (DRIE) Si cavity with a resistively heated membrane floor and a DRIE-Si cap containing >1500 parallel diffusion channels, each 54 × 54 × 200 µm. The cavity is packed with 750 µg of a commercial graphitized carbon adsorbent. Fluidic and heat-transfer modeling was used to guide the design process to ensure power-efficient sample transfer during thermal desorption. Experiments performed with toluene at concentrations of ~1 ppm gave a constant sampling rate of 9.1 mL min(-1) for up to 30 min, which is within 2% of theoretical predictions and corresponds to a linear dynamic mass uptake range of ~1 µg. The cavity membrane could be heated to 250 °C in 0.23 s with 1 W of applied power and, with 50 mL min(-1) of suction flow provided by a downstream pump, yielded >95% desorption/injection efficiency of toluene samples over an 8-fold range of captured mass.