Biocompatible APTES–PEG Modified Magnetite Nanoparticles: Effective Carriers of Antineoplastic Agents to Ovarian Cancer

Magnetite nanoparticles are particularly attractive for drug delivery applications because of their size-dependent superparamagnetism, low toxicity, and biocompatibility with cells and tissues. Surface modification of iron oxide nanoparticles with biocompatible polymers is potentially beneficial to prepare biodegradable nanocomposite-based drug delivery agents for in vivo and in vitro applications. In the present study, the bare (10 nm) and polyethylene glycol (PEG)–(3-aminopropyl)triethoxysilane (APTES) (PA) modified (17 nm) superparamagnetic iron oxide nanoparticles (SPIO NPs) were synthesized by coprecipitation method. The anticancer drugs, doxorubicin (DOX) and paclitaxel (PTX), were separately encapsulated into the synthesized polymeric nanocomposites for localized targeting of human ovarian cancer in vitro. Surface morphology analysis by scanning electron microscopy showed a slight increase in particle size (27?±?0.7 and 30?±?0.45 nm) with drug loading capacities of 70 and 61.5 % and release capabilities of 90 and 93 % for the DOX- and PTX-AP-SPIO NPs, respectively (p?<?0.001). Ten milligrams/milliliter DOX- and PTX-loaded AP-SPIO NPs caused a significant amount of cytotoxicity and downregulation of antiapoptotic proteins, as compared with same amounts of free drugs (p?<?0.001). In vivo antiproliferative effect of present formulation on immunodeficient female Balb/c mice showed ovarian tumor shrinkage from 2,920 to 143 mm³ after 40 days. The present formulation of APTES–PEG-SPIO-based nanocomposite system of targeted drug delivery proved to be effective enough in order to treat deadly solid tumor of ovarian cancer in vitro and in vivo.     

Tuning the primary resonances of a micro resonator,using piezoelectric actuation

Microbeam dynamics is important in MEMS filters and resonators. In this research, the effect of piezoelectric actuation on the resonance frequencies of a piezoelectrically actuated capacitive clamped-clamped microbeam is studied. The microbeam is sandwiched with piezoelectric layers throughout its entire length. The lower piezoelectric layer is exposed to a combination of a DC and a harmonic excitation voltage. The DC electrostatic voltage is applied to prevent the doubling of the excitation frequency. The traditional resonators are tuned using DC electrostatic actuation, which tunes the resonance frequency only in backward direction on the frequency domain. The proposed model enables tuning the resonance frequencies in both forward and backward directions. For small amplitudes of harmonic excitation and high enough quality factor, the frequency response curves obtained by the shooting method are validated with those of the multiple time scales technique. Unlike the perturbation technique, which imposes limitation on both the amplitude of the harmonic excitation and the quality factor to be applicable, the shooting method can be applied to capture the periodic attractors regardless of how big the amplitude of harmonic excitation and the quality factor are.     

Surface Display of Bacterial Metallothioneins and a Chitin Binding Domain on Escherichia coli Increase Cadmium Adsorption and Cell Immobilization

To increase the level of adsorption of cadmium ions to the surface of Escherichia coli, we fused cyanobacterial metallothioneins, SmtA (from Synechococcus elongatus PCC 3601) and MtnA (from Synechococcus vulcanus) to the E. coli cell surface using a Lpp??-OmpA-based display system. E. coli strains expressing Lpp??-OmpA?CSmtA-linker-ChBD (chitin-binding domain from Bacillus pumillus SG2 chitinase S; chiS) and Lpp??-OmpA?CMtnA-linker-ChBD on their surface adsorbed more cadmium compared to the E. coli cells expressing only the Lpp??-OmpA-linker-ChBD hybrid. These constructs also were bound to chitin through their chitin-binding domain, allowing them to be immobilized on a chitin matrix. We assessed surface presentation of Lpp??-OmpA?CSmtA-linker-ChBD, Lpp??-OmpA?CMtnA-linker-ChBD, and Lpp??-OmpA-linker-ChBD using immunostaining. The Lpp??-OmpA?CSmtA-linker-ChBD chimera adsorbed metal and was bound to chitin with the highest efficiency compared to the other chimeras, suggesting that it is an effective bioadsorbent. This is the first example of coupling metal adsorption with cell immobilization using a whole-cell bioadsorbent.     

Microarray-based resequencing by apyrase-mediated allele-specific extension

We have developed an array-based resequencing method to determine genetic alterations in putative cancer genes. The method relies on that the specificity of DNA polymerase in allele-specific extensions can be enhanced by terminating the extension reactions with apyrase and that a tiling set of primers are synthesized covering the investigated gene sequence. We report on such apyrase-mediated allele-specific primer extension (AMASE) assay as a method suitable for high-throughout resequencing and mutation detection in tumor suppressor genes and oncogenes. In the experimental setup, primers complementary to codons 12, 13 and codon 61 of the N-ras proto-oncogene were spotted onto glass slides. Overlapping sense and anti-sense primers were designed so that complementary primers for all possible mutations in each base position were investigated. The extension reactions were performed in a single step following hybridization of target DNA to the immobilized primers on the array surface. Mutation detection limits and the possibility of quantifying the mutations were investigated using synthetic oligonucleotides. In addition, 64 clinical samples were sequenced and 16 of these showed mutations in the N-ras gene.     

Active vibration control using optimized modified acceleration feedback with Adaptive Line Enhancer for frequency tracking

Modified acceleration feedback (MAF) control, an active vibration control method that uses collocated piezoelectric actuators and accelerometer is developed and its gains optimized using an optimal controller. The control system consists of two main parts: (1) frequency adaptation that uses Adaptive Line Enhancer (ALE) and (2) an optimized controller. Frequency adaptation method tracks the frequency of vibrations using ALE. The obtained frequency is then fed to MAF compensators. This provides a unique feature for MAF, by extending its domain of capabilities from controlling a certain mode of vibrations to any excited mode. The optimized MAF controller can provide optimal sets of gains for a wide range of frequencies, based on the characteristics of the system. The experimental results show that the frequency tracking method works quite well and fast enough to be used in a real-time controller. ALE parameters are numerically and experimentally investigated and tuned for optimized frequency tracking. The results also indicate that the MAF can provide significant vibration reduction using the optimized controller. The control power varies for vibration suppression at different resonance frequencies; however, it is always optimized.