Slawomir Jakiela

Acoustic emission for tracing the evolution of damage in wooden objects

Abstract The monitoring of acoustic emission (AE) has allowed direct tracing of the fracturing intensity in wooden cultural objects exposed to variations in temperature and relative humidity (RH). High-frequency components produced by the mechanical fracturing were extracted from the raw AE signals using wavelet transforms. The accumulated energy of these components depended on the magnitude and rate of RH variations. The AE activity became negligible below the allowable magnitude for rapid RH variation established by numerical modelling, or when the time interval allowed for the RH variation was long enough. On-site AE monitoring of a wooden altarpiece in an historic church further confirmed the usefulness of the technique in tracing climate-induced stress in wood. The development of practical AE sensors to indicate risk to wooden objects in museums and at historic sites, or during their transportation, is discussed.

Mitochondria-based biosensors with piezometric and RELS transduction for potassium uptake and release investigations.

Dysfunctional mitochondria appear to be involved in many diseases through their role in respiration, reactive oxygen species generation, and energy production. To aid in the design of new biosensors based on mitochondria (MT), we have investigated the feasibility of detecting ion fluxes through the MT-membrane K+-ion channels using piezosensors with MTs immobilized either by hydrogen bonding or thin polypyrrole (PPy) binding film. We have demonstrated for the first time that the mitochondria-based piezosensors are able to detect ion fluxes and thus be utilized for drug development aimed at ion channel opener- or inhibitor-function. The quartz crystal resonator responding only to mass changes in the lower part of the MT film, penetrated by the acoustic wave, is able to detect a pronounced cationic dynamics in PPy-bonded MT piezosensors despite of the undoped-PPy preference for pure anion dynamics. The control experiments performed by resonance elastic light scattering (RELS) confirmed MT swelling/shrinking, ion dynamics, and osmotic water transfer in MTs, as well as the effects of exposure to a drug valinomycin at sub-nanomolar concentrations.

Enhancement of bacterial growth with the help of immiscible oxygenated oils

Bacterial growth in an aqueous medium in the vicinity of the interface with an immiscible oxygenated fluid is a subject of this study. We analyse the impact of fluids with oxygen solubility much higher than that of water, on the growth rate of Escherichia coli in shaken simple culture tubes. The measurements were conducted continuously in an incubator with the use of a custom-designed detector of scattered light. As a result, we show that oxygenated immiscible fluids transfer oxygen across the interfaces to enhance the maximum growth rate of bacteria, in some cases even to double it. In the present study, we probed six fluids, including hexadecane, silicone oil, fluorinated liquids: FC-40, FC-70, and hydrofluoroethers (HFE): HFE-7200 and HFE-7500. The mechanisms of interfacial phenomena of physio-chemical and hydrodynamic nature have been elucidated.

Optical Biosensing System for the Detection of Survivin mRNA in Colorectal Cancer Cells Using a Graphene Oxide Carrier-Bound Oligonucleotide Molecular Beacon

The anti-apoptotic protein survivin is one of the most promising cancer biomarkers owing to its high expression in human cancers and rare occurrence in normal adult tissues. In this work, we have investigated the role of supramolecular interactions between a graphene oxide (GO) nanosheet nanocarrier and a survivin molecular beacon (SurMB), functionalized by attaching fluorophore Joe and quencher Dabcyl (SurMB-Joe). Molecular dynamics simulations revealed hydrogen bonding of Joe moiety and Dabcyl to GO carriers that considerably increase the SurMB-GO bonding strength. This was confirmed in experimental work by the reduced fluorescence background in the OFF state, thereby increasing the useful analytical signal range for mRNA detection. A new mechanism of hairpin–hairpin interaction of GO@SurMB with target oligonucleotides has been proposed. A low limit of detection, LOD = 16 nM (S/N = 3), has been achieved for complementary tDNA using GO@SurMB-Joe nanocarriers. We have demonstrated an efficient internalization of SurMB-Joe-loaded GO nanocarriers in malignant SW480 cells. The proposed tunability of the bonding strength in the attached motifs for MBs immobilized on nanocarriers, via structural modifications, should be useful in gene delivery systems to enhance the efficacy of gene retention, cell transfection and genomic material survivability in the cellular environment.

Hairpin–Hairpin Molecular Beacon Interactions for Detection of Survivin mRNA in Malignant SW480 Cells

Cancer biomarkers offer unique prospects for the development of cancer diagnostics and therapy. One of such biomarkers, protein survivin (Sur), exhibits strong antiapoptotic and proliferation-enhancing properties and is heavily expressed in multiple cancers. Thus, it can be utilized to provide new modalities for modulating the cell-growth rate, essential for effective cancer treatment. Herein, we have focused on the development of a new survivin-based cancer detection platform for colorectal cancer cells SW480 using a turn-on fluorescence oligonucleotide molecular beacon (MB) probe, encoded to recognize Sur messenger RNA (mRNA). Contrary to the expectations, we have found that both the complementary target oligonucleotide strands as well as the single- and double-mismatch targets, instead of exhibiting the anticipated simple random conformations, preferentially formed secondary structure motifs by folding into small-loop hairpin structures. Such a conformation may interfere with, or even undermine, the biorecognition process. To gain better understanding of the interactions involved, we have replaced the classical Tyagi-Kramer model of interactions between a straight target oligonucleotide strand and a hairpin MB with a new model to account for the hairpin-hairpin interactions as the biorecognition principle. A detailed mechanism of these interactions has been proposed. Furthermore, in experimental work, we have demonstrated an efficient transfection of malignant SW480 cells with SurMB probes containing a fluorophore Joe (SurMB-Joe) using liposomal nanocarriers. The green emission from SurMB-Joe in transfected cancer cells, due to the hybridization of the SurMB-Joe loop with Sur mRNA hairpin target, corroborates Sur overexpression. On the other hand, healthy human-colon epithelial cells CCD 841 CoN show only negligible expression of survivin mRNA. These experiments provide the proof-of-concept for distinguishing between the cancer and normal cells by the proposed hairpin-hairpin interaction method. The single nucleotide polymorphism sensitivity and a low detection limit of 26 nM (S/N = 3σ) for complementary targets have been achieved.

A Portable Tool for the Evaluation of Microclimate Conditions within Museum Enclosures, Transit Frames, and Transport Cases

There has been an increase in interest in the quality of environments generated within protective enclosures used for art objects. Evidence of this is in the activities of recent projects that have...