Biosensors for the Isolation and Detection of Circulating Tumor Cells (CTCs) in Point-of-Care Settings

Circulating tumor cells (CTCs) are cells that have been shed from tumors and circulate in the bloodstream. These cells can also be responsible for further metastases and the spread of cancer. Taking a closer look and analyzing CTCs through what has come to be known as "liquid biopsy" has immense potential to further researchers' understanding of cancer biology. However, CTCs are very sparse and are therefore difficult to detect and capture. To combat this issue, researchers have attempted to create devices, assays, and further techniques to successfully isolate CTCs for analysis. In this work, new and existing biosensing techniques for CTC isolation, detection, and release/detachment are discussed and compared to evaluate their efficacy, specificity, and cost. Here, we specifically aim to evaluate and identify the potential success of these techniques and devices in point-of-care (POC) settings.

The Use of Hydrogels for the Treatment of Bone Osteosarcoma via Localized Drug-Delivery and Tissue Regeneration: A Narrative Review

Osteosarcoma is a malignant tumor of bone that leads to poor mortality and morbidity. Management of this cancer through conventional methods involves invasive treatment options that place patients at an increased risk of adverse events. The use of hydrogels to target osteosarcoma has shown promising results both in vitro and in vivo to eradicate tumor cells while promoting bone regeneration. The loading of hydrogels with chemotherapeutic drugs provides a route for site-specific targeted therapy for osteosarcoma. Current studies demonstrate tumor regression in vivo and lysis of tumor cells in vitro when exposed to doped hydrogel scaffolds. Additionally, novel stimuli-responsive hydrogels are able to react with the tissue microenvironment to facilitate the controlled release of anti-tumor drugs and with biomechanical properties that can be modulated. This narrative review of the current literature discusses both in vitro and in vivo studies of different hydrogels, including stimuli-responsive, designed to treat bone osteosarcoma. Future applications to address patient treatment for this bone cancer are also discussed.

3D Printed Osteoblast-Alginate/Collagen Hydrogels Promote Survival, Proliferation and Mineralization at Low Doses of Strontium Calcium Polyphosphate

The generation of biomaterials via 3D printing is an emerging biotechnology with novel methods that seeks to enhance bone regeneration. Alginate and collagen are two commonly used biomaterials for bone tissue engineering and have demonstrated biocompatibility. Strontium (Sr) and Calcium phosphate (CaP) are vital elements of bone and their incorporation in composite materials has shown promising results for skeletal repair. In this study, we investigated strontium calcium polyphosphate (SCPP) doped 3D printed alginate/collagen hydrogels loaded with MC3T3-E1 osteoblasts. These cell-laden scaffolds were crosslinked with different concentrations of 1% SCPP to evaluate the effect of strontium ions on cell behavior and the biomaterial properties of the scaffolds. Through scanning electron microscopy and Raman spectroscopy, we showed that the scaffolds had a granular surface topography with the banding pattern of alginate around 1100 cm^-1 and of collagen around 1430 cm^-1. Our results revealed that 2 mg/mL of SCPP induced the greatest scaffold degradation after 7 days and least amount of swelling after 24 h. Exposure of osteoblasts to SCPP induced severe cytotoxic effects after 1 mg/mL. pH analysis demonstrated acidity in the presence of SCPP at a pH between 2 and 4 at 0.1, 0.3, 0.5, and 1 mg/mL, which can be buffered with cell culture medium. However, when the SCPP was added to the scaffolds, the overall pH increased indicating intrinsic activity of the scaffold to buffer the SCPP. Moreover, cell viability was observed for up to 21 days in scaffolds with early mineralization at 0.3, 0.5, and 1 mg/mL of SCPP. Overall, low doses of SCPP proved to be a potential additive in biomaterial approaches for bone tissue engineering; however, the cytotoxic effects due to its pH must be monitored closely.

Microfluidic Devices for HIV Diagnosis and Monitoring at Point-of-Care (POC) Settings

Human immunodeficiency virus (HIV) is a global epidemic; however, many individuals are able to obtain treatment and manage their condition. Progression to acquired immunodeficiency syndrome (AIDS) occurs during late-stage HIV infection, which compromises the immune system, making it susceptible to infections. While there is no cure, antiretroviral therapy can be used provided that detection occurs, preferably during the early phase. However, the detection of HIV is expensive and resource-intensive when tested with conventional methods, such as flow cytometry, polymerase chain reaction (PCR), or enzyme-linked immunosorbent assays (ELISA). Improving disease detection in resource-constrained areas requires equipment that is affordable, portable, and can deliver rapid results. Microfluidic devices have transformed many benchtop techniques to on-chip detection for portable and rapid point-of-care (POC) testing. These devices are cost-effective, sensitive, and rapid and can be used in areas lacking resources. Moreover, their functionality can rival their benchtop counterparts, making them efficient for disease detection. In this review, we discuss the limitations of currently used conventional HIV diagnostic assays and provide an overview of potential microfluidic technologies that can improve HIV testing in POC settings.

Controlled Biodegradation and Swelling of Strontium-doped Alginate/Collagen Scaffolds for Bone Tissue Engineering

Treatment for critical size defects (CSDs) in bone often use bone grafts to act as a scaffold to help complete healing. Biological scaffolds require bone extraction from the individual or an outside donor while synthetic grafts mostly suffer from poor degradation kinetics and decreased bioactivity. In this study, we investigated a 3D printed scaffold derived from a novel composite bioink composed of alginate and collagen augmented with varying doses from 2 m g/ m L to 20 m g/ m L of 1% strontium-calcium polyphosphate (SCPP) to control biodegradability and fluid uptake. Scaffolds with increased SCPP concentrations showed higher particle density, lesser swelling ratio and greater biodegradability indicating that these critically important properties for bone healing are fine-tunable and highly dependent on SCPP dosing. Clinical Relevance- The dosing of 1% SCPP into porous alginate/collagen scaffolds provides adjustable long-term degradation and material properties suitable for potential in vivo CSD applications.

Bioprinting of Stem Cells in Multimaterial Scaffolds and Their Applications in Bone Tissue Engineering

Bioprinting stem cells into three-dimensional (3D) scaffolds has emerged as a new avenue for regenerative medicine, bone tissue engineering, and biosensor manufacturing in recent years. Mesenchymal stem cells, such as adipose-derived and bone-marrow-derived stem cells, are capable of multipotent differentiation in a 3D culture. The use of different printing methods results in varying effects on the bioprinted stem cells with the appearance of no general adverse effects. Specifically, extrusion, inkjet, and laser-assisted bioprinting are three methods that impact stem cell viability, proliferation, and differentiation potential. Each printing method confers advantages and disadvantages that directly influence cellular behavior. Additionally, the acquisition of 3D bioprinters has become more prominent with innovative technology and affordability. With accessible technology, custom 3D bioprinters with capabilities to print high-performance bioinks are used for biosensor fabrication. Such 3D printed biosensors are used to control conductivity and electrical transmission in physiological environments. Once printed, the scaffolds containing the aforementioned stem cells have a significant impact on cellular behavior and differentiation. Natural polymer hydrogels and natural composites can impact osteogenic differentiation with some inducing chondrogenesis. Further studies have shown enhanced osteogenesis using cell-laden scaffolds in vivo. Furthermore, selective use of biomaterials can directly influence cell fate and the quantity of osteogenesis. This review evaluates the impact of extrusion, inkjet, and laser-assisted bioprinting on adipose-derived and bone-marrow-derived stem cells along with the effect of incorporating these stem cells into natural and composite biomaterials.

Ruptured Intracranial Aneurysms Treated with the Pipeline Embolization Device: A Systematic Review and Pooled Analysis of Individual Patient Data

BACKGROUND

The Pipeline Embolization Device (PED) is a flow-diverting stent for the treatment of intracranial aneurysms and is used off-label for a subset of ruptured aneurysms not amenable to traditional treatment.

PURPOSE

Our aim was to evaluate the safety and efficacy of the PED for treatment of ruptured intracranial aneurysms.

DATA SOURCES

A systematic review of the MEDLINE, EMBASE, and Scopus data bases from January 2011 to March 2020 was performed for articles reporting treatment of ruptured intracranial aneurysms with the PED.

STUDY SELECTION

A total of 12 studies comprising 145 patients with 145 treated aneurysms were included for analysis.

DATA ANALYSIS

Individual patient data were collected. Nonparametric tests were used to compare differences among patients. Logistic regression was used to determine an association with outcome variables.

DATA SYNTHESIS

Mean aneurysm size was 5.9 mm, and most were blister (51.0%) or dissecting (26.9%) in morphology. Three (2.1%) aneurysms reruptured following PED placement. Univariate logistic regression identified larger aneurysm size as a significant predictor of aneurysm rerupture (P = .008). Of patients with radiographic follow-up, 87.5% had complete aneurysm occlusion. Symptomatic neurologic complications occurred in 16.5%.

LIMITATIONS

Analysis was limited by the quality of the included data, most of which were from small case series representing class III medical evidence. No study assessed outcome in a blinded or independently adjudicated manner.

CONCLUSIONS

Most ruptured aneurysms treated with the PED were blister or dissecting aneurysms. Treatment was associated with a rerupture rate of 2.1% and a complete occlusion rate of 87.5%.

Early pregnancy biochemical markers of placentation for screening of gestational diabetes mellitus (GDM)

For the effective management and screening of patients with diabetes, lipid profile has been a useful mean. Here, we hypothesized that biochemical analyses of blood serum in pregnant women with GDM will develop an insight on the pathogenesis of the disease and possibly uncover new biomarkers. In order to test our hypothesis, antenatal pregnant women (n = 300) were selected for blood samples including 176 with positive clinical/family history and 124 with negative clinical/family history of GDM during the early second trimester (14-18 weeks of gestation). All the subjects were followed up to the early third trimester (24-28 weeks of gestation) for second sampling until the onset of GDM. Lipid profile data shows that mean values of triglycerides, total cholesterol, low density lipids and very low density lipids were significantly higher (p < 0.05) and mean HDL was significantly lower in early second trimester in those patients who subsequently developed GDM during late third trimester when compared with those who didn't develop GDM. Inflammatory biomarker such as High-sensitivity C-reactive protein (hs-CRP) levels were also found to be significantly higher by 69% increase in patients who developed GDM later in third trimester in comparison with those who didn't develop. About 32% patients who finally developed GDM belonged to positive clinical/family history group. The results of our study indicate that abnormal serum cholesterol; triglycerides, HDL, LDL, VLDL and hs-CRP play a vital in pathophysiology of gestational diabetes. Early diagnosis of GDM based on these biochemical markers will help decrease adverse neonatal and maternal outcomes.

Rapid Regeneration of Vascularized Bone by Nanofabricated Amorphous Silicon Oxynitrophosphide (SiONP) Overlays

Fracture healing is a complex biological process. Severe bone loss and ischemia from traumatic fractures lead to inflammation and accumulation of damaging reactive oxygen species (ROS). Fixative devices that not only provide mechanical support but also stimulate antioxidants such as superoxide dismutase (SOD1) and influence signaling pathways for extracellular matrix (ECM) mineralization, are critical for normal healing of such fractures. In this study, we report a novel biomaterial, silicon oxynitrophosphide (SiONP) that provides sustained release of ionic silicon (Si⁺⁴) and phosphorous (P) over few weeks under physiological conditions. Anti-oxidant role of Si⁺⁴ and augmented ECM mineralization by P ions lead to enhanced osteogenesis coupled with quick revascularization for rapid bone regeneration. Plasma enhanced chemical vapor deposition (PECVD) provided a conformal, well adherent and highly reproducible surface chemistry overlaid onto nanofabricated bioinspired surfaces. The Nitrogen to P and O content ratio was observed to change the dissolution rate and the release kinetics of the overlaid film. The SiONP films with optimal release kinetics promoted anti-oxidant expression via enhanced SOD1, which downstream upregulated other osteogenic markers with MC3T3-E1 cells. These surfaces also promoted angiogenesis evident by formation of thicker tubules by Human umbilical vein endothelial cells (HUVEC). In-vivo evaluation using a rat critical-sized calvarial defect model showed rapid bone-regeneration for these nanofabricated biomaterials as compared to control groups, and opens new horizon for future clinical trials of new antioxidant materials on biomedical devices that can reduce healing time, lower medical care cost, and increase the quality of newly formed bone in critical size defects.

Circulating tumor cell isolation, culture, and downstream molecular analysis

Circulating tumor cells (CTCs) are a major contributor of cancer metastases and hold a promising prognostic significance in cancer detection. Performing functional and molecular characterization of CTCs provides an in-depth knowledge about this lethal disease. Researchers are making efforts to design devices and develop assays for enumeration of CTCs with a high capture and detection efficiency from whole blood of cancer patients. The existing and on-going research on CTC isolation methods has revealed cell characteristics which are helpful in cancer monitoring and designing of targeted cancer treatments. In this review paper, a brief summary of existing CTC isolation methods is presented. We also discuss methods of detaching CTC from functionalized surfaces (functional assays/devices) and their further use for ex-vivo culturing that aid in studies regarding molecular properties that encourage metastatic seeding. In the clinical applications section, we discuss a number of cases that CTCs can play a key role for monitoring metastases, drug treatment response, and heterogeneity profiling regarding biomarkers and gene expression studies that bring treatment design further towards personalized medicine.

Role of Hydrogen and Nitrogen on the Surface Chemical Structure of Bioactive Amorphous Silicon Oxynitride Films

Silicon oxynitride (Si-O-N) is a new biomaterial in which its O/N ratio is tunable for variable Si release and its subsequent endocytotic incorporation into native hydroxyapatite for enhanced bone healing. However, the effect of nitrogen and hydrogen bonding on the formation and structure of hydroxyapatite is unclear. This study aims to uncover the roles of H and N in tuning Si-O-N surface bioactivity for hydroxyapatite formation. Conformal Si-O-N films were fabricated by plasma-enhanced chemical vapor deposition (PECVD) onto Ti/Si substrates. Fourier transform infrared spectroscopy (FTIR) and Rutherford backscattering spectrometry (RBS) analysis indicated increased Si-H and N-H bonding with increased N content. Surface energy decreased with increased N content. X-ray absorbance near edge structure (XANES) analysis showed tetrahedral coordination in O-rich films and trigonal coordination in N-rich films. O-rich films exhibited a 1:1 ratio of 2p3/2 to 2p1/2 electron absorbance, while this ratio was 1.73:1 for N-rich films. Both Si and N had a reduced partial charge for both O- and N-rich films, whereas O maintained its partial charge for either film. O-rich films were found to exhibit random bonding SizOxNy, while N-rich films exhibited random mixing: [Si-Si]-[Si-O]-[Si-N]. Thus, hydrogen bonding limits random nitrogen bonding in Si-O-N films via surface Si-H and N-H bonding. Moreover, increased nitrogen content reduces the partial charge of constituent elements and changes the bonding structure from random bonding to random mixing.

Amorphous Silica: A New Antioxidant Role for Rapid Critical-Sized Bone Defect Healing

Traumatic fractures cause structurally unstable sites due to severe bone loss. Such fractures generate a high yield of reactive oxygen species (ROS) that can lead to oxidative stress. Excessive and prolonged ROS activity impedes osteoblast differentiation and instigates long healing times. Stimulation of antioxidants such as superoxide dismutase (SOD1), are crucial to reduce ROS, stimulate osteogenesis, and strengthen collagen and mineral formation. Yet, no current fixative devices have shown an ability to enhance collagen matrix formation through antioxidant expression. This study reports plasma-enhanced chemical vapor deposition based amorphous silicon oxynitride (Si(ON)x) as a potential new fracture healing biomaterial that adheres well to the implant surface, releases Si(+4) to enhance osteogenesis, and forms a surface hydroxyapatite for collagen mineral attachment. These materials provide a sustained release of Si(+4) in physiological environment for extended times. The dissolution rate partially depends on the film chemistry and can be controlled by varying O/N ratio. The presence of Si(+4) enhances SOD1, which stimulates other osteogenic markers downstream and leads to rapid mineral formation. In vivo testing using a rat critical-sized calvarial defect model shows a more rapid bone-regeneration for these biomaterials as compared to control groups, that implies the clinical significance of the presented biomaterial.

Differentiating Metastatic and Non-metastatic Tumor Cells from Their Translocation Profile through Solid-State Micropores

Cancer treatment, care, and outcomes are much more effective if started at early stages of the disease. The presence of malignant cancer cells in human samples such as blood or biopsied tissue can be used to reduce overtreatment and underdiagnosis as well as for prognosis monitoring. Reliable quantification of metastatic tumor cells (MTCs) and non-metastatic tumor cells (NMTCs) from human samples can help in cancer staging as well. We report a simple, fast, and reliable approach to identify and quantify metastatic and non-metastatic cancer cells from whole biological samples in a point-of-care manner. The metastatic (MDA MB-231) and non-metastatic (MCF7) breast cancer cells were pushed through a solid-state micropore made in a 200 nm thin SiO2 membrane while measuring current across the micropore. The cells generated very distinctive translocation profiles. The translocation differences stemmed from their peculiar mechanophysical properties. The detection efficiency of the device for each type of tumor cells was ∼75%. MTCs showed faster translocation (36%) and 34% less pore blockage than NMTCs. The micropore approach is simple, exact, and quantitative for metastatic cell detection in a lab-on-a chip setting, without the need for any preprocessing of the sample.

Residual organic matter and microbial respiration in bottom ash: Effects on metal leaching and eco-toxicity

A common assumption regarding the residual organic matter, in bottom ash, is that it does not represent a significant pool of organic carbon and, beyond metal-ion complexation process, it is of little consequence to evolution of ash/leachate chemistry. This article evaluates the effect of residual organic matter and associated microbial respiratory processes on leaching of toxic metals (i.e. arsenic, copper, chromium, molybdenum, nickel, lead, antimony and zinc), eco-toxicity of ash leachates. Microbial respiration was quantified with help of a respirometric test equipment OXITOP control system. The effect of microbial respiration on metal/residual organic matter leaching and eco-toxicity was quantified with the help of batch leaching tests and an eco-toxicity assay - Daphnia magna. In general, the microbial respiration process decreased the leachate pH and eco-toxicity, indicating modification of bioavailability of metal species. Furthermore, the leaching of critical metals, such as copper and chromium, decreased after the respiration in both ash types (fresh and weathered). It was concluded that microbial respiration, if harnessed properly, could enhance the stability of fresh bottom ash and may promote its reuse.

Enhanced interfacial adhesion and osteogenesis for rapid "bone-like" biomineralization by PECVD-based silicon oxynitride overlays

Structurally unstable fracture sites require metal fixative devices, which have long healing times due to their lack of osteoinductivity. Bioactive glass coatings lack in interfacial bonding, delaminate, and have reduced bioactivity due to the high temperatures used for their fabrication. Here, we test the hypothesis that low-temperature PECVD amorphous silica can enhance adhesion to the underlying metal surface and that N incorporation enhances osteogenesis and rapid biomineralization. A model Ti/TiO2-SiOx interface was formed by first depositing Ti onto Si wafers, followed by surface patterning, thermal annealing to form TiO2, and depositing SiOx/Si(ON)x overlays. TEM micrographs showed conformal SiOx layers on Ti/TiO2 overlays while XPS data revealed the formation of an elemental Ti-O-Si interface. Nanoscratch testing verified strong SiOx bonding with the underlying TiO2 layers. In vitro studies showed that the surface properties changed significantly to reveal the formation of hydroxycarbonate apatite within 6 h, and Si(ON)x surface chemistry induced osteogenic gene expression of human periosteal cells and led to a rapid "bone-like" biomineral formation within 4 weeks. XANES data revealed that the incorporation of N increased the surface HA bioactivity by increasing the carbonate to phosphate ratio. In conclusion, silicon oxynitride overlays on bone-implant systems enhance osteogenesis and biomineralization via surface nitrogen incorporation.

Effects of substrate induced respiration on the stability of bottom ash in landfill cover environment

The municipal solid waste incineration bottom ash is being increasingly used to construct landfill covers in Sweden. In post-closure, owing to increased cover infiltration, the percolating water can add external organic matter to bottom ash. The addition and subsequent degradation of this external organic matter can affect metal mobility through complexation and change in redox conditions. However, the impacts of such external organic matter addition on bottom ash stability have not been fully evaluated yet. Therefore, the objective of this study was to evaluate the impact of external organic matter on bottom ash respiration and metal leaching. The samples of weathered bottom ash were mixed with oven dried and digested wastewater sludge (1%-5% by weight). The aerobic respiration activity (AT4), as well as the leaching of metals, was tested with the help of respiration and batch leaching tests. The respiration and heavy metal leaching increased linearly with the external organic matter addition. Based on the results, it was concluded that the external organic matter addition would negatively affect the quality of landfill cover drainage.

Synthesis of nano-textured biocompatible scaffolds from chicken eggshells

Cell adhesion, morphology and growth are influenced by surface topography at nano and micrometer scales. Nano-textured surfaces are prepared using photolithography, plasma etching and long polymer chemical etching which are cost prohibitive and require specialized equipment. This article demonstrates a simple approach to synthesize nano-textured scaffolds from chicken eggshells. Varieties of pattern are made on the eggshells like micro-needle forests and nanopores, giving very uniform nano-textures to the surfaces. The surfaces are characterized for chemical composition and crystal phase. The novel patterns are transferred to PDMS surfaces and the nano-textured PDMS surfaces are used to study the effect of texturing on human fibroblast cell growth and attachment. The effects of surface topographies, along with laminin coating on cell cultures, are also studied. We find an exciting phenomenon that the initial seeding density of the fibroblast cells affects the influence of the nano-texturing on cell growth. These nano-textured surfaces give 16 times more fibroblast growth when compared to flat PDMS surfaces. The novel nano-textured patterns also double the laminin adsorption on PDMS.

Electrical detection of cancer biomarker using aptamers with nanogap break-junctions

Epidermal growth factor receptor (EGFR) is a cell surface protein overexpressed in cancerous cells. It is known to be the most common oncogene. EGFR concentration also increases in the serum of cancer patients. The detection of small changes in the concentration of EGFR can be critical for early diagnosis, resulting in better treatment and improved survival rate of cancer patients. This article reports an RNA aptamer based approach to selectively capture EGFR protein and an electrical scheme for its detection. Pairs of gold electrodes with nanometer separation were made through confluence of focused ion beam scratching and electromigration. The aptamer was hybridized to a single stranded DNA molecule, which in turn was immobilized on the SiO(2) surface between the gold nanoelectrodes. The selectivity of the aptamer was demonstrated by using control chips with mutated non-selective aptamer and with no aptamer. Surface functionalization was characterized by optical detection and two orders of magnitude increase in direct current (DC) was measured when selective capture of EGFR occurred. This represents an electronic biosensor for the detection of proteins of interest for medical applications.

Electrical fingerprinting, 3D profiling and detection of tumor cells with solid-state micropores

Solid-state micropores can provide direct information of ex vivo or in vitro cell populations. Micropores are used to detect and discriminate cancer cells based on the translocation behavior through micropores. The approach provides rapid detection of cell types based on their size and mechano-physical properties like elasticity, viscosity and stiffness. Use of a single micropore device enables detection of tumor cells from whole blood efficiently, at 70% CTC detection efficiency. The CTCs show characteristic electrical signals which easily distinguish these from other cell types. The approach provides a gentle and inexpensive instrument that can be used for specific blood analysis in a lab-on-a-chip setting. The device does not require any preprocessing of the blood sample, particles/beads attachment, surface functionalization or fluorescent tags and provides quantitative and objective detection of cancer cells.

Pulsed plasma polymerization for controlling shrinkage and surface composition of nanopores

Solid-state nanopores have emerged as sensors for single molecules and these have been employed to examine the biophysical properties of an increasingly large variety of biomolecules. Herein we describe a novel and facile approach to precisely adjust the pore size, while simultaneously controlling the surface chemical composition of the solid-state nanopores. Specifically, nanopores fabricated using standard ion beam technology are shrunk to the requisite molecular dimensions via the deposition of highly conformal pulsed plasma generated thin polymeric films. The plasma treatment process provides accurate control of the pore size as the conformal film deposition depends linearly on the deposition time. Simultaneously, the pore and channel chemical compositions are controlled by appropriate selection of the gaseous monomer and plasma conditions employed in the deposition of the polymer films. The controlled pore shrinkage is characterized with high resolution AFM, and the film chemistry of the plasma generated polymers is analyzed with FTIR and XPS. The stability and practical utility of this new approach is demonstrated by successful single molecule sensing of double-stranded DNA. The process offers a viable new advance in the fabrication of tailored nanopores, in terms of both the pore size and surface composition, for usage in a wide range of emerging applications.

Shrinking of Solid-state Nanopores by Direct Thermal Heating

Solid-state nanopores have emerged as useful single-molecule sensors for DNA and proteins. A novel and simple technique for solid-state nanopore fabrication is reported here. The process involves direct thermal heating of 100 to 300 nm nanopores, made by focused ion beam (FIB) milling in free-standing membranes. Direct heating results in shrinking of the silicon dioxide nanopores. The free-standing silicon dioxide membrane is softened and adatoms diffuse to a lower surface free energy. The model predicts the dynamics of the shrinking process as validated by experiments. The method described herein, can process many samples at one time. The inbuilt stress in the oxide film is also reduced due to annealing. The surface composition of the pore walls remains the same during the shrinking process. The linear shrinkage rate gives a reproducible way to control the diameter of a pore with nanometer precision.

Molecular specificity of L2 monoclonal antibodies that bind to carbohydrate determinants of neural cell adhesion molecules and their resemblance to other monoclonal antibodies recognizing the myelin-associated glycoprotein

L2 monoclonal antibodies and HNK-1 have been shown to bind to related carbohydrate determinants in the myelin-associated glycoprotein (MAG) and several adhesion molecules of the nervous system including neural cell adhesion molecule (N-CAM), L1 and J1. It is shown here that MAG is the principal component in human white matter binding the L2 antibodies, but the most prominent antigens with the L2 epitopes in human gray matter are of higher Mr. It is also shown that the L2 antibodies resemble HNK-1 in binding to some 19-28 kDa glycoproteins and some sulfated, glucuronic acid-containing sphingoglycolipids of the peripheral nervous system (PNS). In addition, monoclonal and polyclonal antibodies raised to human MAG are shown to cross react with bovine N-CAM due to the presence of common carbohydrate constituents. The results further emphasize the shared antigenicity between MAG, N-CAM and other adhesion molecules. In addition, they demonstrate that the L2 antibodies belong to a family of monoclonal antibodies (including HNK-1, human IgM paraproteins associated with neuropathy, and others) that are characterized by reactivity against carbohydrate determinants shared by human MAG, the 19-28 kDa glycoproteins of the PNS and the sulfated, glucuronic acid-containing sphingoglycolipids of the PNS.