Pekka Hanninen

• Professor
• Dean at University of Turku

Complex or unknown liquid analysis re-quires extensive instrumentation and laboratory work - simple field devices have usually serious limitations in functionality, sensitivity and applicability. This com-munication presents a novel, effective and simple ap-proach to fingerprinting liquids. The method is based on non-specific interactions of the sa...

The imaging behavior of a two-photon excitation 4Pi confocal microscope in a real biological sample was investigated. In addition, methods for exploiting the full resolution potential of 4Pi confocal microscopy were developed. Based on the observations, it was found that two-photon 4Pi confocal microscopy is indeed feasible for microscopical resear...

Two-photon excitation fluorescence imaging is feasible with continuous wave lasers. Images of biological specimens are obtained by employing photon counting in conjunction with an increased recording time. The approach allows two-photon three-dimensional imaging of fluorescently labelled specimens with inexpensive lasers.

Bioaffinity binding assays such as the immunoassay are widely used in life science research. In an immunoassay, specific antibodies are used to bind target molecules in the sample, and quantification of the binding reaction reveals the amount of the target molecules. Here we present a method to measure bioaffinity assays using the two-photon excita...

Optics has been in the headlines this year due to the UN-sponsored International Year of Light 2015 (IYL 2015), and due to its presence in the 2014 Nobel Prize awards. The purpose of this article is to highlight the innovation-enabling elements that were behind the work of one of the Nobel Laureates-and the stream of innovations that followed, beyo...

The Mini Fluorescence Microscope (MFM), developed by Aboa Space Research Oy (ASRO) in collaboration with the University of Turku (UTU), is a un ultra-compact instrument aimed at enhancing space-based live cell imaging capabilities. The instrument is designed to address key challenges in space research, such as cellular responses to microgravity and...

Understanding how the space environment affects biological systems has become important now that manned space exploration missions beyond the low Earth orbit are again in the roadmaps. The International Space Station, ISS, is an ideal site to study the effects of gravity on biological systems, not only because of the microgravity environment, but a...

The ability of cells to migrate is a fundamental physiological process involved in embryonic development, tissue homeostasis, immune surveillance, and wound healing. Therefore, the mechanisms governing cellular locomotion have been under intense scrutiny over the last 50 years. One of the main tools of this scrutiny is live-cell quantitative imagin...

The ability of cells to migrate is a fundamental physiological process involved in embryonic development, tissue homeostasis, immune surveillance, and wound healing. Therefore, the mechanisms governing cellular locomotion have been under intense scrutiny over the last 50 years. One of the main tools of this scrutiny is live-cell quantitative imagin...

The ability of cells to migrate is a fundamental physiological process involved in embryonic development, tissue homeostasis, immune surveillance, and wound healing. Therefore, the mechanisms governing cellular locomotion have been under intense scrutiny over the last 50 years. One of the main tools of this scrutiny is live-cell quantitative imagin...

Actin and myosins (IIA, IIB, and X) generate mechanical forces in osteoclasts that drive functions such as migration and membrane trafficking. In neurofibromatosis, these processes are perturbed due to a mutation in neurofibromatosis type 1 (NF1) gene. This mutation leads to generation of hyperactive bone-resorbing osteoclasts that increases incide...

Preparing pioloform/formvar support films on transmission electron microscopy (TEM) grids is a routine laboratory procedure in practically all electron microscopy units. In current practice, these grids are manually placed on the support film one by one using special tweezers, a process requiring a steady hand. The work is often ergonomically awkwa...

The objective of this study is to introduce the usefulness of the liquid fingerprinting technology in spotting potential health hazards in foodstuff, exemplifying milk. The presented method relies on the use of long lifetime photoluminescent europium chelate and individual cross-reactive modulators in an array form. Here, we demonstrate the potency...

Fluorescent nanodiamonds are presented here as dual-contrast imaging probes for intracellular correlation using super-resolution stimulated emission depletion and transmission electron microscopy. This correlative light and electron microscopy probe is demonstrated to be suitable for live cell imaging, fixed cell imaging, and further, super-resolut...

Development of fluorescent and electron dense markers is essential for the implementation of correlative light and electron microscopy, as dual-contrast landmarks are required to match the details in the multimodal images. Here, a novel method for correlative microscopy that utilizes fluorescent nanodiamonds (FNDs) as dual-contrast probes is report...

Correlative light and electron microscopy (CLEM) allows combining the advantages of fluorescence microscopy and electron microscopy for cell imaging. Rare phenomenon expressing cells can be studied by specifically tagged fluorophores with fluorescence microscopy. Subsequently, cells can be fixed and ultra-structural details can be studied with tran...

In this paper, cellular management of fluorescent nanodiamonds (FNDs) has been studied for better understanding in the design for potential applications of FNDs in biomedicine. The FNDs have shown to be photostable probes for bioimaging and thus are well-suited, for example, long-term tracking purposes. The FNDs also exhibit good biocompatibility a...

Intracellular Trafficking of Fluorescent Nanodiamonds and Regulation of Their Cellular Toxicity

Thyrotropin or thyroid-stimulating hormone (TSH) is used as a marker for thyroid function. More precise and more sensitive immunoassays are needed to facilitate continuous monitoring of thyroid dysfunctions and to assess the efficacy of the selected therapy and dosage of medication. Moreover, most thyroid diseases are autoimmune diseases making TSH...

Biocatalytic pulp fibres were prepared using surface functionalization of bleached kraft pulp with amino groups (F) and further immobilization of a cross-linked glucose oxidase (G*) from Aspergillus niger. The cross-linked enzymes (G*) were characterized using X-ray spectroscopy, Fourier transform infrared spectroscopy, dynamic scanning calorimetry...

Scientific Reports 6 : Article number: 28962 10.1038/srep28962 ; published online: 01 July 2016 ; updated: 19 August 2016 . In this Article, the PyImageQualityRanking software source code has been omitted from the Methods section under subheading ‘Image Quality Ranking Software’.

Automated analysis of microscope images is necessitated by the increased need for high-resolution follow up of events in time. Manually finding the right images to be analyzed, or eliminated from data analysis are common day-to-day problems in microscopy research today, and the constantly growing size of image datasets does not help the matter. We...

Characterizing and/or determining a sample employs an array of at least two of different interacting surfaces, at least one of which comprises a non-specific interacting material non-specifically interacting said sample,at least one labelling reactant, and/or combination of the sample and at least one labelling reactant. The sample and at least one...

We demonstrate the use of saline mouth rinse and chemical fingerprinting approach in screening for oral lesions from tobacco product using patients in low-resource settings in rural India. The method is based on the use of a nonspecific long lifetime luminescent lanthanide label, time-resolved measurement and modulator chemistry that is sensitive t...

To elucidate processes in the osteoclastic bone resorption, visualise resorption and related actin reorganisation, a combination of imaging technologies and an applicable in vitro model is needed. Nanosized bone powder from matching species is deposited on any biocompatible surface in order to form a thin, translucent, smooth and elastic representa...

The samples were characterized and / or measured, using an array of at least two different surface interactions has, which include at least one non-specific interactions material, with the sample, at least one labeled reactant, and / or sample and at least one composition of reactants interacting non-specifically labeled. Introducing the sample and...

An apparatus and method are disclosed for examining optically a sample carried in a plurality of wells. A holder is adapted to receive and hold in place a sample carrier. A plurality of excitation means selectively introduce excitation towards a spatially limited portion of a sample carrier held in place by said holder. Detecting means receive and...

A method for generating three-dimensional tomograms from multiple three-dimensional axial projections in STimulated Emission Depletion (STED) superresolution microscopy is introduced. Our STED< method, based on the use of a micromirror placed on top of a standard microscopic sample, is used to record a three-dimensional projection at an oblique ang...

Recently reported photoluminescent nanographene oxides (nGO), i.e. nanographene oxidised with sulfuric to nitric acid mixture (SNOx method), have tuneable photoluminescence and are scalable, simple and fast to produce optical probes. This material belongs to the vast class of photoluminescent carbon nanostructures, including carbon dots, nanodiamon...

A method utilizing competitive adsorption between polyethylene glycols (PEGs) and labeled protein to nanoparticles was developed for the determination of PEG molecular weight (MW) in a microtiter plate format. Two mix-and-measure systems, time-resolved luminescence resonance energy transfer (TR-LRET) with donor europium(III) polystyrene nanoparticl...

Multi-modal correlative microscopy allows combining the strengths of several imaging techniques to provide unique contrast. However it is not always straightforward to setup instruments for such customized experiments, as most microscope manufacturers use their own proprietary software, with limited or no capability to interface with other instrume...

We present a tomographic Stimulated Emission Depletion (STED) microscopy method with three-dimensional superresolution, and its application to osteoclast bone resorption study. In order to improve axial resolution in standard STED system by tomography, two axial projections were obtained by imaging a sample at two different angles; one conventional...

Systolic time intervals (STI) have significant diagnostic values for a clinical assessment of the left ventricle in adults. This study was conducted to explore the feasibility of using seismocardiography (SCG) to measure the systolic timings of the cardiac cycle accurately. An algorithm was developed for the automatic localization of the cardiac ev...

Scale inhibitors are used extensively in the oil and gas industry to provide the level of flow assurance required to maximise safe and economic hydrocarbon production. For both continuous and scale squeeze treatments, residual inhibitor concentrations need to be verified on a continual basis to assure the field operator that the implemented scale m...

In stimulated emission depletion (STED) microscopy, the lateral resolution is in the range of tens of nanometers depending on the sample and the instrument. The axial resolution, however, is in standard systems limited by diffraction to about 500 nm. We present an approach to three-dimensional diffraction-unlimited resolution by observing the sampl...

A quenching resonance energy transfer (QRET) assay for small GTPase nucleotide exchange kinetic monitoring is demonstrated using nanomolar protein concentrations. Small GTPases are central signaling proteins in all eukaryotic cells acting as a "molecular switches" that are active in the GTP-state and inactive in the GDP-state. GTP-loading is highly...

The ultraviolet (UV) and visible (Vis) parts of the electromagnetic spectra have been utilized in bioanalytical spectroscopy from its early years in both academia and industry. This was mostly facilitated by the easy availability of relatively inexpensive instrumentation and the spectral properties of biomolecules. A significant part of biomolecule...

A non-competitive homogeneous, single-label quenching resonance energy transfer (QRET) assay for protein quantification is now presented using lanthanide-chelate labeled nucleic acid aptamers. A labeled ssDNA aptamer binding to a growth factor has been successfully used to provide luminescence signal protection of the lanthanide label. The QRET tec...

Background and Aims: A novel, rapid and simple liquid fingerprinting technology is described and demonstrated for wine identification and for quality control. Method and Results: The wine sample, selected chemical modulators on the surfaces of an array, and a long lifetime luminescent europium label interact non-specifically providing a unique lumi...

Scale inhibitors are used extensively in the oil and gas industry to provide the level of flow assurance required to maximise safe and economic hydrocarbon production. For both continuous and scale squeeze treatments, residual inhibitor concentrations need to be verified on a continual basis to assure the field operator that the implemented scale m...

Nanoparticle-based method utilizing time-resolved luminescence resonance energy transfer (TR-LRET) was developed for molecular weight determination. This mix-and-measure nanoparticle method is based on the competitive adsorption between the sample and the acceptor-labeled protein to donor Eu(III) nanoparticles. The size-dependent adsorption of mole...

Nanoparticle labels have enhanced the performance of diagnostic, screening, and other measurement applications and hold further promise for more sensitive, precise, and cost-effective assay technologies. Nevertheless, a clear view of the biomolecular interactions on the molecular level is missing. Controlling the ratio of molecular recognition over...

Background: We present here the first application of 2-photon excited fluorescence detection (TPX) technology for the direct screening of clinical colonization samples for methicillin-resistant Staphylococcus aureus (MRSA). Methods: A total of 125 samples from 14 patients with previously identified MRSA carriage and 16 controls from low-prevalen...

This study, a homogeneous assay system for delta opioid receptor binding ligands has been developed using Quenching Resonance Energy Transfer (QRET). The QRET system allows receptor-ligand binding assays on intact cells using a single-label approach and a nonspecific quenching mechanism. Binding of antagonists or agonists to the receptor can be def...

A stable liposome-based time-resolved luminescence resonance energy transfer (TR-LRET) assay was developed based on the interaction of biotinylated lipids and streptavidin. Eu(3+) ion chelated to 4,4,4-trifluoro-1-(2-naphthalenyl)-1,3-butanedione and trioctylphosphine oxide was incorporated into liposomes. Acceptor-labeled streptavidin bound to bio...

Recent advances within materials science and its interdisciplinary applications in biomedicine have emphasized the potential of using a single multifunctional composite material for concurrent drug delivery and biomedical imaging. Here we present a novel composite material consisting of a photoluminescent nanodiamond (ND) core with a porous silica...

A homogeneous time-resolved luminescence resonance energy transfer (TR-LRET) assay has been developed to quantify proteins. The competitive assay is based on resonance energy transfer (RET) between two luminescent nanosized particles. Polystyrene nanoparticles loaded with Eu(3+) chelates (EuNPs) act as donors, while protein-coated quantum dots (QDs...

A novel easy-to-use homogeneous method utilizing two-photon excitation (TPX) for quantification of proteins or counting of eukaryotic cells in solution has been developed. This highly-sensitive technique is based on the adsorption competition between the sample and fluorescently labeled protein to micron-sized carboxylate modified polystyrene parti...

Two homogeneous assay systems have been combined to provide a new cell-based functional assay. Assay can be used to identify ligand binding to ß2-adrenergic receptors, but also the downstream response can be determined in the same assay. Both the quenching resonance energy transfer (QRET) and the DiscoveRx PathHunter™ assay formats allow the use of...

Adsorption of sample protein to Eu(3+) chelate-labeled nanoparticles is the basis of the developed noncompetitive and homogeneous method for the estimation of the protein isoelectric point (pI). The lanthanide ion of the nanoparticle surface-conjugated Eu(3+) chelate is dissociated at a low pH, therefore decreasing the luminescence signal. A nanopa...

A sensitive mix-and-measure method for the determination of protein and cell concentrations was developed. It is based on the competitive adsorption between the analyte and donor- and acceptor-labeled proteins to carboxylate-modified polystyrene nanoparticles. A high time-resolved luminescence resonance energy transfer (TR-LRET) signal is detected...

A sensitive and rapid assay for the quantification of proteins, based on sample protein adsorption to Eu(3+)-chelate-labeled nanoparticles, was developed. The lanthanide ion of the surface-conjugated Eu(3+) chelate is dissociated at a low pH, decreasing the luminescence signal. The increased concentration of the sample protein prevents dissociation...

Besides the typical short-lived fluorescence with decay times in the nanosecond range, colloidal II/VI semiconductor nanoparticles dispersed in buffer also possess a long-lived fluorescence component with decay times in the microsecond range. Here, the signal intensity of the long-lived luminescence at microsecond range is shown to increase 1,000-f...

Mutations of the small GTP-binding protein Ras have been commonly found in tumors, and Ras oncogenes have been established to be involved in the early steps of cancerogenesis. The detection of Ras activity is critical in the determination of the cell signaling events controlling cell growth and differentiation. Therefore, development of improved me...

Homogeneous luminescence-based microplate assays are desirable in high-throughput screening of new nuclear receptor regulators. Time-resolved fluorescence resonance energy transfer (TR-FRET) assays provide high sensitivity due to low background signal. The TR-FRET concept requires labeling of both ligand and receptor, making the assay format and it...

Minimally invasive optical glucose biosensors with increased functional longevity form one of the most promising techniques for continuous glucose monitoring, because of their long-term stability, reversibility, repeatability, specificity, and high sensitivity. They are based on the principle of competitive binding and fluorescence resonance energy...

The aim of this study was to evaluate a new type of assay for the phenotypic detection of methicillin-resistant Staphylococcus aureus (MRSA). The assay is based on a point-of-care compatible two-photon excitation fluorescence detection technology (TPX). A collection of 243 epidemic MRSA isolates was tested in addition to 138 sporadic MRSA and 101 n...

The unique properties of lanthanides as analytical luminophores may only be efficiently exploited when the measuring instrument has been especially designed for this particular purpose. Nowadays, many commercial plate fluorometers can be equipped for time-resolved measurements. However, not all of them perform to the limits of the luminophores: tim...

A luminometric method for quantitative cell surface protein expression analysis has been developed in a microtiter plate format. The method is based on immunocytochemistry, the use of long-lived europium(III) and terbium(III) chelates and platinum(II) porphyrin luminescence labels in addition to short-lived syto13 DNA stain, and detection of photol...

Nanoparticle assay utilizing time-resolved luminescence resonance energy transfer (TR-LRET) was developed for the detection of protein aggregation. This mix-and-measure nanoparticle assay is based on the competitive adsorption of the sample and the acceptor-labeled protein to donor europium(III) polystyrene particles. The protein aggregation was de...

G-protein-coupled receptors (GPCRs) are an important class of pharmaceutical drug targets. Functional high-throughput GPCR assays are needed to test an increasing number of synthesized novel drug compounds and their function in signal transduction processes. Measurement of changes in the cyclic adenosine monophosphate (cAMP) concentration is a wide...

The behaviour of binding reactions in immunoassays can be predicted and studied by modelling methods. Simple antibody-analyte binding reaction kinetics can be simulated by e.g. a mechanistic assay model based on differential equations. However, the mathematical modelling becomes more complicated if multivalent-structured components are involved and...

We have developed easy-to-use homogeneous methods utilizing time-resolved fluorescence resonance energy transfer (TR-FRET) and fluorescence quenching for quantification of eukaryotic cells. The methods rely on a competitive adsorption of cells and fluorescently labeled protein onto citrate-stabilized colloidal gold nanoparticles or carboxylate-modi...

Functional cell signaling assays have become important tools for measuring ligand-induced receptor activation in cell-based biomolecular screening. Guanosine-5'-triphosphate (GTP) is a generic signaling marker responsible for the first intracellular signaling event of the G-protein-coupled receptors (GPCRs). [(35)S]GTPgammaS binding assay is the cl...

The time-resolved fluorescence technique, quenching resonance energy transfer, QRET, relies on a single-labeled binding partner in combination with a soluble quencher. The quencher reduces efficiently the fluorescence of the unbound labeled ligand, whereas the fluorescence of the bound fraction is detectable. This approach allows the development of...

Rapid microtiter assays that utilize the time-resolved fluorescence resonance energy transfer or quenching of dye-labeled proteins adsorbed onto the surfaces of polystyrene or maghemite nanoparticles have been developed for the detection and quantification of trace amounts of surfactants at concentrations down to 10 nM.

A fullerenol sensor utilizing fluorescence quenching of a labeled protein was developed for rapid detection and quantification of ionic (cetyltriammonium bromide (CTAB), sodium dodecyl sulphate, (SDS)) and non-ionic (Tween 20 and Triton X-100) surfactants in solution. The sensor is based on the competitive adsorption of the surfactants and the fluo...

The feasibility of dissolved-core alginate-templated fluorescent microspheres as "smart tattoo" glucose biosensors was investigated in simulated interstitial fluid (SIF). The sensor works on the principle of competitive binding and fluorescence resonance energy transfer. The sensor consists of multilayer thin film coated alginate microspheres incor...

In this article, a single-label separation-free fluorescence technique is presented as a potential screening method for cell-based receptor antagonists and agonists.The time-resolved fluorescence technique, quenching resonance energy transfer (QRET), relies on a single-labeled binding partner in combination with a soluble quencher. The quencher eff...

Microtiter wells are commonly used for bioassays. The sensitivity of such an assay depends on several instrumental and biochemical parameters such as the signal-to-background ratio and nonspecific binding of the label molecules. In this study, we have investigated the possible effects of well surface defects, well edges and denaturation of capture...

A variety of particles have been adopted as solid support in bioaffinity assays, and the ability to modify the particle properties makes them a versatile tool in assay development. In separation-free fluorescence resonance energy transfer (FRET) assays, fluorescent particles have been used as donors and acceptors due to their high binding capacity...

A new easy-to-use method for quantification of proteins in solution has been developed. It is based on adsorption competition of the sample protein and fluorescently labeled bovine serum albumin (BSA) onto gold particles. The protein concentration is determined by observing the magnitude of fluorescence altered by quenching the fluorescence on the...

High-sensitivity, high-throughput, and user-friendly lanthanide-based assays for receptor-ligand interactions provide an attractive alternative to the traditional radioligand displacement assays. In this study, three small-molecule pindolol ligand derivatives were synthesized and their binding properties were tested in a radioligand displacement as...

Nanoparticle labels have been shown to improve the sensitivity of a sandwich immunoassay significantly. Further improvement in sensitivity is limited by nonspecific binding of the nanoparticle labels. Here, an experimental characterization of assay performance was carried out using clinically important analytes thyroid stimulating hormone and prost...

Lanthanide chelates and lanthanide nanoparticle labels are attractive donors for separation-free time-resolved fluorescence resonance energy transfer (TR-FRET) assays. In fully dyed nanoparticles, the inner volume of nanoparticle labels in TR-FRET assays are incapable of participating to energy transfer due to large distances to acceptors on the su...

There is an increasing need for developing simple assay formats for biomedical screening purposes. Assays on cell membranes have become important in studies of receptor–ligand interactions and signal pathways. Here luminescence energy transfer was studied on liposomes containing europium ion chelated to 4,4,4-trifluoro-1-(2-naphthalenyl)-1,3-butane...

Rapid, high-throughput screening tools are needed to contain the spread of hospital-acquired methicillin (meticillin)-resistant Staphylococcus aureus (MRSA) strains. Most techniques used in current clinical practice still require time-consuming culture for primary isolation of the microbe. We present a new phenotypic assay for MRSA screening. The t...