Identification of Risk Factors for Bisphosphonate-Associated Atypical Femoral Fractures and Osteonecrosis of the Jaw in a Pharmacovigilance Database.

BACKGROUND: Atypical femoral fractures (AFs) and osteonecrosis of the jaw (ONJ) are well-known adverse drug reactions (ADRs) associated with bisphosphonates. To prevent these ADRs and to aid in the search for pathogenic mechanisms, knowledge of risk factors can be helpful. OBJECTIVE: To identify risk factors for bisphosphonate-related ONJ and AF. METHODS: In this case-control study of reports of bisphosphonate-related ADRs from February 16, 1984, to October 16, 2013, in the Swedish national database of ADRs, we compared characteristics for cases of ONJ (n = 167) and AF (n = 55) with all other bisphosphonate-related ADRs (n = 565) with regard to demographic variables, clinical characteristics, and concomitant drug treatments. We adjusted for multiple comparisons with Bonferroni correction. RESULTS: Time to onset of ADRs differed statistically significantly between cases of AF and controls (2156 vs 111 days). For ONJ versus controls, differences were statistically significant for time to onset (1240 vs 111 days), intravenous administration (40% vs 20%), dental procedures (49% vs 0.2%) and prostheses (5% vs 0%), cancer disease (44% vs 12%), multiple myeloma (21% vs 1%), rheumatoid arthritis (14% vs 5%), and treatment with antineoplastic agents and oxycodone. CONCLUSION: These results lend further evidence to previously identified risk factors for ONJ-that is, intravenous bisphosphonate administration; invasive dental procedures and dental prostheses; cancer disease, in particular multiple myeloma; and possibly, long-term bisphosphonate treatment. A putative further risk factor is rheumatoid arthritis. Only long-term bisphosphonate treatment was more common among AF cases. The lack of overlap of risk factors between ONJ and AF suggests different pathogenic mechanisms.

Novel readout method for molecular diagnostic assays based on optical measurements of magnetic nanobead dynamics.

We demonstrate detection of DNA coils formed from a Vibrio cholerae DNA target at picomolar concentrations using a novel optomagnetic approach exploiting the dynamic behavior and optical anisotropy of magnetic nanobead (MNB) assemblies. We establish that the complex second harmonic optical transmission spectra of MNB suspensions measured upon application of a weak uniaxial AC magnetic field correlate well with the rotation dynamics of the individual MNBs. Adding a target analyte to the solution leads to the formation of permanent MNB clusters, namely, to the suppression of the dynamic MNB behavior. We prove that the optical transmission spectra are highly sensitive to the formation of permanent MNB clusters and, thereby to the target analyte concentration. As a specific clinically relevant diagnostic case, we detect DNA coils formed via padlock probe recognition and isothermal rolling circle amplification and benchmark against a commercial equipment. The results demonstrate the fast optomagnetic readout of rolling circle products from bacterial DNA utilizing the dynamic properties of MNBs in a miniaturized and low-cost platform requiring only a transparent window in the chip.

Magnetophoretic Transport Line System for Rapid On-Chip Attomole Protein Detection.

A lab-on-a-chip traveling wave magnetophoresis approach for sensitive and rapid protein detection is reported. In this method, a chip-based magnetic microarray comprising lines of micrometer-sized thin film magnetic elements was used to control the movement of magnetic beads (MBs). The MBs and the chip were functionalized, forming a sandwich-type assay. The MBs were transported across a detection area, and the presence of target molecules resulted in the immobilization of MBs within this area. Target quantification was accomplished by MB counting in the detection area using an optical microscope. In order to demonstrate the versatility of the microarray, biotinylated antiavidin was selected as the target protein. In this case, avidin-functionalized MBs and an avidin-functionalized detection area were used. With a total assay time of 1 to 1.5 h (depending on the labeling approach used), a limit of detection in the attomole range was achieved. Compared to on-chip surface plasmon resonance biodetection systems, our method has a larger dynamic range and is about a factor of 500 times more sensitive. Furthermore, our MB transportation system can operate in any chip-based biosensor platform, thereby significantly improving traditional biosensors.

On-chip detection of rolling circle amplified DNA molecules from Bacillus globigii spores and Vibrio cholerae.

For the first time DNA coils formed by rolling circle amplification are quantified on-chip by Brownian relaxation measurements on magnetic nanobeads using a magnetoresistive sensor. No external magnetic fields are required besides the magnetic field arising from the current through the sensor, which makes the setup very compact. Limits of detection down to 500 Bacillus globigii spores and 2 pM of Vibrio cholerae are demonstrated, which are on the same order of magnitude or lower than those achieved previously using a commercial macro-scale AC susceptometer. The chip-based readout is an important step towards the realization of field tests based on rolling circle amplification molecular analyses.

Blu-ray optomagnetic measurement based competitive immunoassay for Salmonella detection.

A turn-on competitive immunoassay using a low-cost Blu-ray optomagnetic setup and two differently sized magnetic particles (micron-sized particles acting as capture particles and nano-sized particles acting as detection particles) is here presented. For Salmonella detection, a limit of detection of 8×10(4)CFU/mL is achieved within a total assay time of 3h. The combination of a competitive strategy and an optomagnetic setup not only enables a turn-on read-out format, but also results in a sensitivity limit about a factor of 20 times lower than of volumetric magnetic stray field detection device based immunoassays. The improvement of sensitivity is enabled by the formation of immuno-magnetic aggregates providing steric hindrance protecting the interior binding sites from interaction with the magnetic nanoparticle labels. The formation of immuno-magnetic aggregates is confirmed by fluorescence microscopy. The system exhibits no visible cross-reaction with other common pathogenic bacteria, even at concentrations as high as 10(7)CFU/mL. Furthermore, we present results when using the setup for a qualitative and homogeneous biplex immunoassay of Escherichia coli and Salmonella typhimurium.

Optomagnetic read-out enables easy, rapid, and cost-efficient qualitative biplex detection of bacterial DNA sequences.

There is an increasing need to develop novel bioassay methods for low-cost, rapid, and easy-to-use multiplex detection of pathogens in various fields ranging from human infectious disease diagnosis, drinking water quality control, to food safety applications. Due to their unique advantages, magnetic and optomagnetic bioassay principles are particularly promising for biodetection platforms that will be used in developing countries. In this paper, an optomagnetic method for rapid and cost-efficient qualitative biplex detection of bacterial DNA sequences is demonstrated. Within less than two hours, the assay gives an answer to whether none, both, or only one of the bacterial DNA sequences is present in the sample. The assay relies on hybridization of oligonucleotide-functionalized magnetic nanobeads of two different sizes to rolling circle amplification (RCA) products originating from two different bacterial targets. The different bead sizes are equipped with different oligonucleotide probes, complementary to only one of the RCA products, and the read-out is carried out in the same sample volume. In an optomagnetic setup, the frequency modulation of transmitted laser light in response to an applied AC magnetic field is measured. The presented methodology is potentially interesting for low-cost screening of pathogens relating to both human and veterinary medicine in resource-poor regions of the world.

Turn-on optomagnetic bacterial DNA sequence detection using volume-amplified magnetic nanobeads.

Detection of a Vibrio cholerae DNA-sequence using an optomagnetic read-out exploiting the dynamic behavior of magnetic nanobeads along with two turn-on data analysis approaches is demonstrated. The optomagnetic method uses a weak uniaxial AC magnetic field of varying frequency applied perpendicular to the optical path and measures the modulation of laser light passing through a cuvette containing the sample with oligonucleotide-tagged magnetic beads and macromolecular coils of single-stranded DNA. The DNA coils are formed upon a padlock probe ligation followed by rolling circle amplification (RCA). The presence of target gives rise to a change of the 2nd harmonic component, V2=V2(')+iV2(''), of the transmitted light. We demonstrate that by using the phase angle ξ defined as ξ=arctanV2(')/V2('') in the low-frequency region we obtain a limit of detection of 10pM for an RCA time of only 20min corresponding to a total assay time of 60min. Moreover, we show that the approach based on ξ is significantly more robust than the analysis based on a turn-off of the signal due to free magnetic nanobeads used in previous work (Donolato et al., submitted for publication), where a limit of detection of 10pM was obtained for an RCA time of 60min. The increased robustness and the reduction in total assay time constitute significant steps towards the realization of a low-cost, rapid and sensitive biosensor platform suitable for pathogen detection in both human and veterinary medicine settings.