Properties and biomedical applications of magnetic nanoparticles

Magnetic nanoparticles have a number of unique properties, making them promising agents for applications in medicine including magnetically targeted drug delivery, magnetic hyperthermia, magnetic resonance imaging, and radiation therapy. They are biocompatible and can also be coated with biocompatible surfactants, which may be further functionalized with optically and therapeutically active molecules. These nanoparticles can be manipulated with non-invasive external magnetic field to produce heat, target specific site, and monitor their distribution in vivo. Within this framework, we have investigated a number of biomedical applications of these nanoparticles. We synthesized a thermosensitive microgel with iron oxide adsorbed on its surface. An alternating magnetic field applied to these nanocomposites heated the system and triggered the release of an anticancer drug mitoxantrone . We also parameterized the chain length dependence of drug release from dextran coated iron oxide nanoparticles, finding that both the release rate and equilibrium release fraction depend on the molecular mass of the surfactant. Finally, we also localized dextran coated iron oxide nanoparticles labeled with tat peptide to the cell nucleus, which permits this system to be used for a variety of biomedical applications. Beyond investigating magnetic nanoparticles for biomedical applications, we also studied their magnetohydrodynamic and dielectric properties in solution. Magnetohydrodynamic properties of ferrofluid can be controlled by appropriate selection of surfactant and deielctric measurement showed magnetodielectric coupling in this system. We also established that some complex low temperature spin structures are suppressed in Mn3O4 nanoparticles, which has important implications for nanomagnetic devices. Furthermore, we explored exchange bias effects in Ni-NiO core-shell nanoparticles. Finally, we also performed extensive magnetic studies in nickel metalhydride (NiMH) batteries to determine the size of Ni clusters, which plays important role on catalyzing the electrochemical reaction and powering Ni-MH batteries

Effects of Varying Sufactant Chain Lenghts on the Magnetic, Optical and Hyperthermia Properties of Ferrofluids

We report studies of the structural, magnetic, magneto-thermal and magneto-optic properties of dextran, oleic acid, lauric acid and myristic acid surfacted Fe3O4 nanoparticles of hydrodynamic sizes ranging from 32 nm to 92 nm. All the samples showed saturation magnetization of ̃50 emu/g, significantly smaller than the bulk value for Fe3O4, together with superparamagnetic behavior. The ac magnetization measurements on the dextran coated nanoparticles showed frequency dependent blocking temperature, consistent with superparamgnetic blocking. The ferrofluid heating rates in a 250 Gauss, 100 kHz ac magnetic field varied with the chain lengths of the surfactants, with higher heating rates for longer chains. DC-magnetic-field-induced light scattering patterns produced by two orthogonal He-Ne laser beams passing through the ferrofluid sample revealed different optical signatures for different surfactants

Mean Tip Apex Distance in Patients undergoing Dynamic Hip Screw Fixation for Pertrochanteric Fractures without using Traction Table: A Descriptive Cross-sectional Study

Introduction: Dynamic Hip Screw fixation has shown to be equally effective compared to cephalomedullary nailing. The effectiveness of dynamic hip screw fixation for pertrochanteric fractures without using traction table is not well investigated. This study aimed to find out the mean tip apex distance in patients undergoing dynamic hip screw fixation for pertrochanteric fractures without using traction table. Methods: A descriptive cross-sectional study was conducted among patients undergoing dynamic hip screw fixation for pertrochanteric fractures without using traction table between 1 September 2021 and 30 June 2022, after getting approval from institutional review committee (Reference number: IRC-2021-08-23-02). All patients undergoing dynamic hip screw fixation for pertrochanteric fractures without using traction table were included in the study. Patients with pre-existing ipsilateral or contralateral hip deformity, contra-lateral hip prosthesis, bilateral hip fractures, and history of prior ipsilateral hip surgeries were excluded. Point estimate and 95% confidence interval were calculated. Results: Among 45 patients, the mean tip apex distance was 20.45±6.13 mm (18.66-22.24 mm, 95% Confidence Interval). Among 45 patients, 24 (53.33%) were males and 21 (46.66%) were females. The average age of the participants was 67.75±21.33 years. Conclusions: The mean tip apex distance in patients undergoing dynamic hip Screw fixation for pertrochanteric fractures without using traction table was similar to that reported in other international studies

Need of Improvement in Emergency Medical Service in Urban Cities

Introduction: An effective Emergency Medical Service system does not exist in Nepal. For an effective EMS system to be developed the scale of the problem and the existing facilities need to be studied. Methods: Prospective observational study was carried out on 1964 patients attending Emergency Department at Patan Hospital during one month period of September 2006. The patients were specifically enquired on mode of transport used, place of origin and whether they called for an ambulance or not. Patients triage category at the time of triaging was also noted. Information on ambulance service were collected by direct interview with the service providers and the total number of patients attending Emergency Departments daily were collected from the major hospitals of the urban Lalitpur and Kathmandu. MS Excel and SPSS software were used for data entry, editing and analysis. Results: Total 9.9% patients arrived in ambulance whereas 53.6% came in a Taxi, 11.4% came in private vehicle, 13.5 % came by bus, 5.4% came by bike and the rest 6.2% came by other modes of transportation. Only 13.5% of triage category I patients took the ambulance. There were 31 service providers with 49 ambulances and 720 patients per day attend Emergency Departments in the surveyed area. Conclusions: Very less number of patients use the ambulance service for emergency services. The available ambulances are not properly equipped and do not have trained staff and as such are only a means of transportation to the hospitals of urban Lalitpur and Kathmandu. Key Words: ambulance, emergency medical service, para-medics, triage Need of Improvement in Emergency Medical Service in Urban Cities Gongal R,1 Dhungana B, 1 Regmi S, 1 Nakarmi M,2 Yadav B 1 1 Patan Hospital, Lalitpur, Nepal, 2 Health Care Foundation, Kathmandu, Nepal Correspondence: Dr. Rajesh Gongal Department of Surgery Patan Hospital, Patan, Nepal. Email: [email protected] ORIGINAL ARTICLE J Nepal Med Assoc 2009;48(174):139-43 INTRODUCTION The sophisticated Emergency Medical Service (EMS) is limited to developed country only. Many developing countries are now slowly developing such system although most services are localized to the urban areas. 1-5 Although inadquate ambulance services are available in the capital city of Nep

Parametric characterization of penumbra reduction for aperture-collimated pencil beam scanning (PBS) proton therapy

Recently, a commercial treatment planning system (TPS) has implemented aperture collimators for PBS dose calculations which can serve to reduce lateral penumbra. This study characterized the variation in magnitude of lateral penumbra for collimated and un-collimated PBS fields versus the parameters of air gap, depth, and range shifter thickness. Comparisons were performed in a homogenous geometry between measured data and calculations made by a commercial TPS. Beam-specific target volumes were generated for collimated and un-collimated PBS fields and optimized for various range shifter thicknesses and air gaps. Lateral penumbra (80%-20% distance) was measured across each target volume to characterize penumbra variation with depth and air gap. An analytic equation was introduced to predict the reduction in lateral penumbra between un-collimated and collimated PBS treatments. Calculated penumbra values increased with depth across all combinations of range shifters for a constant air gap. At 2 cm depth, the reductions in penumbra due to the aperture were 2.7 mm, 3.7 mm and 4.2 mm when using range shifter thicknesses of 0 cm, 4.0 cm and 7.5 cm, respectively. At a depth of approximately 20 cm and air gap of 5 cm, differences between penumbras of collimated and un-collimated beams were less than 1 mm. Penumbra reductions for the collimated beams were largest at small air gaps. All TPS-calculated penumbra values derived in this study were within 1 mm of film measurement values. Finally, the analytic equation was tested using a clinical CT scan, and we found good dosimetric agreement between the model predictions and the result calculated by the TPS. In conclusion, application of collimators to PBS fields can sharpen penumbra by several mm and are most beneficial for shallow targets. Furthermore, measurements indicate that the dose calculation accuracy in the penumbra region of PBS-collimated fields is adequate for clinical use

Phase-Coexistence and Thermal Hysteresis in Samples Comprising Adventitiously Doped MnAs Nanocrystals: Programming of Aggregate Properties in Magnetostructural Nanomaterials

Small changes in the synthesis of MnAs nanoparticles lead to materials with distinct behavior. Samples prepared by slow heating to 523 K (type-A) exhibit the characteristic magnetostructural transition from the ferromagnetic hexagonal (α) to the paramagnetic orthorhombic (β) phase of bulk MnAs at Tp = 312 K, whereas those prepared by rapid nucleation at 603 K (type-B) adopt the β structure at room temperature and exhibit anomalous magnetic properties. The behavior of type-B nanoparticles is due to P-incorporation (up to 3%), attributed to reaction of the solvent (trioctylphosphine oxide). P-incorporation results in a decrease in the unit cell volume (∼1%) and shifts Tp below room temperature. Temperature-dependent X-ray diffraction reveals a large region of phase-coexistence, up to 90 K, which may reflect small differences in Tp from particle-to-particle within the nearly monodisperse sample. The large coexistence range coupled to the thermal hysteresis results in process-dependent phase mixtures. As-prepared type-B samples exhibiting the β structure at room temperature convert to a mixture of α and β after the sample has been cooled to 77 K and rewarmed to room temperature. This change is reflected in the magnetic response, which shows an increased moment and a shift in the temperature hysteresis loop after cooling. The proportion of α present at room temperature can also be augmented by application of an external magnetic field. Both doped (type-B) and undoped (type-A) MnAs nanoparticles show significant thermal hysteresis narrowing relative to their bulk phases, suggesting that formation of nanoparticles may be an effective method to reduce thermal losses in magnetic refrigeration applications

Validation and practical implementation of seated position radiotherapy in a commercial TPS for proton therapy

© 2020 Associazione Italiana di Fisica Medica Purpose: This work aims to validate new 6D couch features and their implementation for seated radiotherapy in RayStation (RS) treatment planning system (TPS). Materials and methods: In RS TPS, new 6D couch features are (i) chair support device, (ii) patient treatment option of “Sitting: face towards the front of the chair”, and (iii) patient support pitch and roll capabilities. The validation of pitch and roll was performed by comparing TPS generated DRRs with planar x-rays. Dosimetric tests through measurement by 2D ion chamber array were performed for beams created with varied scanning and treatment orientation and 6D couch rotations. For the implementation of 6D couch features for treatments in a seated position, the TPS and oncology information system (Mosaiq) settings are described for a commercial chair. An end-to-end test using an anthropomorphic phantom was performed to test the complete workflow from simulation to treatment delivery. Results: The 6D couch features were found to have a consistent implementation that met IEC 61712 standard. The DRRs were found to have an acceptable agreement with planar x-rays based on visual inspection. For dose map comparison between measured and calculated, the gamma index analysis for all the beams was \u3e95% at a 3% dose-difference and 3 mm distance-to-agreement tolerances. For an end-to end-testing, the phantom was successfully set up at isocenter in the seated position and treatment was delivered. Conclusions: Chair-based treatments in a seated position can be implemented in RayStation through the use of newly released 6D couch features

Effects of Fatty Acid Surfactants on the Magnetic and Magnetohydrodynamic Properties of Ferrofluids

We prepared Fe 3 O 4 magnetic nanoparticles having diameters of approximately 12 nm by chemical coprecipitation, which were coated with three different fatty acid surfactants: oleic acid, lauric acid, and myristic acid. From x-ray diffraction, transmission electron microscopy, and Mössbauer spectroscopy measurements we confirmed that Fe 3 O 4 is the only phase present in the samples. The zero field cooled magnetization curves for the nanoparticles exhibit broad peaks, consistent with superparamagnetic blocking for the polydisperse samples, and a saturation magnetization smaller than that for bulk Fe 3 O 4 . Although there are minimal differences in the magnetic properties of the nanoparticles having different surfactants, we find significant changes in the hydrodynamic response depending on chain length. Hyperthermia measurements show considerably larger response for oleic acid-coated samples, while magneto-optical studies indicate that these samples have slower dynamics of aggregation under the influence of a dc field. These results suggest that the magnetohydrodynamic response of ferrofluids can be controlled by judiciously selecting appropriate surfactants