Liposomes with Caffeic Acid: Morphological and Structural Characterisation, Their Properties and Stability in Time

Medical and pharmaceutical research has shown that liposomes are very efficient in transporting drugs to targets. In this study, we prepared six liposome formulas, three in which we entrapped caffeic acid (CA), and three with only phospholipids and without CA. Determination of entrapment efficiency (EE) showed that regardless of the phospholipids used, the percentage of CA entrapment was up to 76%. The characterization of the liposomes was performed using Dynamic Light Scattering (DLS), Atomic Force Microscopy (AFM), zeta potential and polydispersity and showed that about 75–99% of the liposomes had dimensions between 40 ± 0.55–500 ± 1.45 nm. The size and zeta potential of liposomes were influenced by the type of phospholipid used to obtain them. CA release from liposomes was performed using a six-cell Franz diffusion system, and it was observed that the release of entrapped CA occurs gradually, the highest amount occurring in the first eight hours (over 80%), after which the release is much reduced. Additionally, the time stability of the obtained liposomes was analysed using univariate and multivariate statistical analysis. Therefore, liposomes offer great potential in CA entrapment.

Download Full-text

Simultaneous Determination of E, G and ν of Soft Hydrogels Using Theory of Elasticity

ASME 2009 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2009-204684 ◽

2009 ◽

Author(s):

Uday Chippada ◽

Xue Jiang ◽

Lulu Li ◽

Rene Schloss ◽

Bernard Yurke ◽

...

Keyword(s):

Poisson’S Ratio ◽

Theory Of Elasticity ◽

Complete Characterization ◽

Poisson's Ratio ◽

Force Microscopy ◽

Cellular Processes ◽

Atomic Force ◽

Significant Research

Hydrogels have been used as substrates by many researchers in the study of cellular processes. The mechanical properties of these gels play a significant role in the growth of the cells. Significant research using several methods like compression, indentation, atomic force microscopy and manipulation of beads has been performed in the past to characterize the stiffness of these substrates. However, most of the methods employed assume the gel to be incompressible, with a Poisson’s ratio of 0.5. However, Poisson’s ratio can differ from 0.5. Hence, a more complete characterization of the elastic properties of hydrogels requires that one experimentally obtain the value of at least two of the three quantities: Poisson’s ratio, shear modulus, and elastic modulus.

Download Full-text

Surface characterization of polymer foils

e-Polymers ◽

10.1515/epoly.2012.12.1.960 ◽

2012 ◽

Vol 12 (1) ◽

Cited By ~ 14

Author(s):

Zdenka Kolská ◽

Alena Řezníčková ◽

Václav Švorčík

Keyword(s):

Zeta Potential ◽

Surface Characterization ◽

Streaming Potential ◽

Electrolyte Solutions ◽

Force Microscopy ◽

Angle Measurements ◽

Atomic Force ◽

Contact Angle Measurements ◽

Polymer Foils

AbstractElectrokinetic potential (zeta potential) for selected 21 polymer foils was studied. The results on zeta potential are supplemented with contact angle measurements (goniometry) and with the results on surface roughness measured by atomic force microscopy (AFM). Zeta potential was determined using two approaches: streaming current and streaming potential at pH=6.0-6.2. Two electrolyte solutions with KCl (concentrations 0.001 and 0.005 mol/dm3) and KNO3 (0.001 mol/dm3) were used in the experiments. Zeta potential was shown to depend on surface chemistry, polarity, roughness and morphology of the polymer foils.

Download Full-text

DETERMINATION OF FILLER STRUCTURE IN SILICA-FILLED SBR COMPOUNDS BY MEANS OF SAXS AND AFM

Rubber Chemistry and Technology ◽

10.5254/rct.15.84893 ◽

2015 ◽

Vol 88 (4) ◽

pp. 690-710 ◽

Cited By ~ 6

Author(s):

Jon Otegui ◽

Luis A. Miccio ◽

Arantxa Arbe ◽

Gustavo A. Schwartz ◽

Mathias Meyer ◽

...

Keyword(s):

Force Microscopy ◽

X Ray Scattering ◽

Atomic Force ◽

Filled Rubber ◽

Rubber Compounds ◽

Primary Particles ◽

Styrene Butadiene ◽

Filler Structure

ABSTRACT The structure of the silica particles network in two different solution styrene–butadiene rubbers (S-SBRs) was studied by means of small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM). S-SBR compounds with different silica contents were analyzed in comparison with their oil extended counterparts. A study into the application of SAXS experiments was defined to quantify the structures of silica primary particles and clusters in filled rubber compounds up to very high levels of filler content. We propose a modified structure model that is physically more sound than the widely used Beaucage model and that leads to more robust quantification of the silica structures. In addition, an independent characterization of the filler structure was performed by means of AFM. The cluster and particle sizes deduced from both techniques are in close agreement, supporting the proposed approach. The synergetic application of SAXS and AFM allows a consistent and robust characterization of primary particles and clusters in terms of size and structure. These results were compared and discussed in the framework of previously published works.

Download Full-text

Characterization of Surface Nanostructures on“Thin” Polyolephine Foils

Journal of Nano Research ◽

10.4028/www.scientific.net/jnanor.27.31 ◽

2014 ◽

Vol 27 ◽

pp. 31-39

Author(s):

Alena Řezníčková ◽

Zdeňka Kolská ◽

Petr Sajdl ◽

Václav Švorčík

Keyword(s):

Contact Angle ◽

Surface Properties ◽

Surface Polarity ◽

X Ray ◽

Force Microscopy ◽

Complex Information ◽

Atomic Force ◽

Surface Nanostructures

Surface properties of nanostructures on 7 polyolephine foils were characterized using different analytical methods to discuss an effect of halogen presence in polymer chain to surface properties. Both sides of these foils were examined and compared. Surface roughness and morphology were determined by atomic force microscopy, contact angle by goniometry, surface polarity by electrokinetic analysis. X-ray photoelectron and ultraviolet visible spectroscopies were used for determination of surface chemistry. Combination of different analyses gives complex information about surface properties of the foils, which may be of importance for any future experiments, as well as for their application e.g. in tissue engineering and electronics.

Download Full-text

Micromechanical Characterization of Complex Polypropylene Morphologies by HarmoniX AFM

International Journal of Polymer Science ◽

10.1155/2017/9037127 ◽

2017 ◽

Vol 2017 ◽

pp. 1-12 ◽

Cited By ~ 5

Author(s):

S. Liparoti ◽

A. Sorrentino ◽

V. Speranza

Keyword(s):

Elastic Moduli ◽

Force Microscopy ◽

Atomic Force ◽

Indentation Tests ◽

Injection Molded ◽

Micromechanical Characterization ◽

Complex Polymer ◽

Good Agreement

This paper examines the capability of the HarmoniX Atomic Force Microscopy (AFM) technique to draw accurate and reliable micromechanical characterization of complex polymer morphologies generally found in conventional thermoplastic polymers. To that purpose, injection molded polypropylene samples, containing representative morphologies, have been characterized by HarmoniX AFM. Mapping and distributions of mechanical properties of the samples surface are determined and analyzed. Effects of sample preparation and test conditions are also analyzed. Finally, the AFM determination of surface elastic moduli has been compared with that obtained by indentation tests, finding good agreement among the results.

Download Full-text

Function of Hemoglobin-Based Oxygen Carriers: Determination of Methemoglobin Content by Spectral Extinction Measurements

International Journal of Molecular Sciences ◽

10.3390/ijms22041753 ◽

2021 ◽

Vol 22 (4) ◽

pp. 1753

Author(s):

Kathrin Smuda ◽

Jonas Gienger ◽

Philipp Hönicke ◽

Jörg Neukammer

Keyword(s):

Light Scattering ◽

Cross Sections ◽

Oxygen Carriers ◽

Extinction Cross Section ◽

X Ray ◽

Force Microscopy ◽

Atomic Force ◽

Analytical Centrifugation

Suspensions of hemoglobin microparticles (HbMPs) are promising tools as oxygen therapeutics. For the approval of clinical studies extensive characterization of these HbMPs with a size of about 750 nm is required regarding physical properties, function, pharmaco-kinetics and toxicology. The standard absorbance measurements in blood gas analyzers require dissolution of red blood cells which does not work for HbMP. Therefore, we have developed a robust and rapid optical method for the quality and functionality control of HbMPs. It allows simultaneous determination of the portion of the two states of hemoglobin oxygenated hemoglobin (oxyHb) and deoxygenated hemoglobin (deoxyHb) as well as the content of methemoglobin (metHb). Based on the measurement of collimated transmission spectra between 300 nm and 800 nm, the average extinction cross section of HbMPs is derived. A numerical method is applied to determine the composition of the HbMPs based on their wavelength-dependent refractive index (RI), which is a superposition of the three different states of Hb. Thus, light-scattering properties, including extinction cross sections can be simulated for different compositions and sizes. By comparison to measured spectra, the relative concentrations of oxyHb, deoxyHb, metHb are accessible. For validation of the optically determined composition of the HbMPs, we used X-ray fluorescence spectrometry for the ratio of Fe(II) (oxyHb/deoxyHb) and Fe(III) (metHb). High accuracy density measurements served to access heme-free proteins, size was determined by dynamic light scattering and analytical centrifugation and the shape of the HbMPs was visualized by electron and atomic force microscopy.

Download Full-text

Contact-free experimental determination of the static flexural spring constant of cantilever sensors using a microfluidic force tool

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.7.43 ◽

2016 ◽

Vol 7 ◽

pp. 492-500

Author(s):

John D Parkin ◽

Georg Hähner

Keyword(s):

Noise Spectrum ◽

Spring Constant ◽

Nanoelectromechanical Systems ◽

Force Microscopy ◽

Cantilever Sensors ◽

Atomic Force ◽

Wide Range ◽

Contact Free

Micro- and nanocantilevers are employed in atomic force microscopy (AFM) and in micro- and nanoelectromechanical systems (MEMS and NEMS) as sensing elements. They enable nanomechanical measurements, are essential for the characterization of nanomaterials, and form an integral part of many nanoscale devices. Despite the fact that numerous methods described in the literature can be applied to determine the static flexural spring constant of micro- and nanocantilever sensors, experimental techniques that do not require contact between the sensor and a surface at some point during the calibration process are still the exception rather than the rule. We describe a noncontact method using a microfluidic force tool that produces accurate forces and demonstrate that this, in combination with a thermal noise spectrum, can provide the static flexural spring constant for cantilever sensors of different geometric shapes over a wide range of spring constant values (≈0.8–160 N/m).

Download Full-text

Mechanical Characterization of Torsional Micropaddles Using Atomic Force Microscopy

Journal of Sensors ◽

10.1155/2018/6160907 ◽

2018 ◽

Vol 2018 ◽

pp. 1-7 ◽

Cited By ~ 1

Author(s):

N. Mahmoodi ◽

A. Sabouri ◽

J. Bowen ◽

C. J. Anthony ◽

P. M. Mendes

Keyword(s):

Atomic Force Microscopy ◽

Focused Ion Beam ◽

Ion Beam ◽

Spring Constant ◽

Simple Method ◽

Force Microscopy ◽

Atomic Force ◽

Torsional Spring

The reference cantilever method is shown to act as a direct and simple method for determination of torsional spring constant. It has been applied to the characterization of micropaddle structures similar to those proposed for resonant functionalized chemical sensors and resonant thermal detectors. It is shown that this method can be used as an effective procedure to characterize a key parameter of these devices and would be applicable to characterization of other similar MEMS/NEMS devices such as micromirrors. In this study, two sets of micropaddles are manufactured (beams at centre and offset by 2.5 μm) by using LPCVD silicon nitride as a substrate. The patterning is made by direct milling using focused ion beam. The torsional spring constant is achieved through micromechanical analysis via atomic force microscopy. To obtain the gradient of force curve, the area of the micropaddle is scanned and the behaviour of each pixel is investigated through an automated developed code. The experimental results are in a good agreement with theoretical results.

Download Full-text

Application of instrumented nanoindentation in preformulation studies of pharmaceutical active ingredients and excipients

Acta Pharmaceutica ◽

10.1515/acph-2016-0032 ◽

2016 ◽

Vol 66 (3) ◽

pp. 303-330 ◽

Cited By ~ 14

Author(s):

Mateja Egart ◽

Biljana Janković ◽

Stane Srčič

Keyword(s):

Mechanical Response ◽

Active Ingredients ◽

Force Microscopy ◽

Atomic Force ◽

Accuracy And Precision ◽

Response To Stress ◽

Preformulation Studies ◽

Elastic And Plastic Deformation

Abstract Nanoindentation allows quantitative determination of a material’s response to stress such as elastic and plastic deformation or fracture tendency. Key instruments that have enabled great advances in nanomechanical studies are the instrumented nanoindenter and atomic force microscopy. The versatility of these instruments lies in their capability to measure local mechanical response, in very small volumes and depths, while monitoring time, displacement and force with high accuracy and precision. This review highlights the application of nanoindentation for mechanical characterization of pharmaceutical materials in the preformulation phase (primary investigation of crystalline active ingredients and excipients). With nanoindentation, mechanical response can be assessed with respect to crystal structure. The technique is valuable for mechanical screening of a material at an early development phase in order to predict and better control the processes in which a material is exposed to stress such as milling and compression.

Download Full-text

On the Determination of Mechanical Properties of Aqueous Microgels—Towards High-Throughput Characterization

Gels ◽

10.3390/gels7020064 ◽

2021 ◽

Vol 7 (2) ◽

pp. 64

Author(s):

Ingrid Haga Oevreeide ◽

Renata Szydlak ◽

Marcin Luty ◽

Husnain Ahmed ◽

Victorien Prot ◽

...

Keyword(s):

Mechanical Properties ◽

High Throughput ◽

High Speed ◽

Soft Matter ◽

Force Microscopy ◽

Fluid Field ◽

Atomic Force ◽

Fundamental Point

Aqueous microgels are distinct entities of soft matter with mechanical signatures that can be different from their macroscopic counterparts due to confinement effects in the preparation, inherently made to consist of more than one domain (Janus particles) or further processing by coating and change in the extent of crosslinking of the core. Motivated by the importance of the mechanical properties of such microgels from a fundamental point, but also related to numerous applications, we provide a perspective on the experimental strategies currently available and emerging tools being explored. Albeit all techniques in principle exploit enforcing stress and observing strain, the realization differs from directly, as, e.g., by atomic force microscope, to less evident in a fluid field combined with imaging by a high-speed camera in high-throughput strategies. Moreover, the accompanying analysis strategies also reflect such differences, and the level of detail that would be preferred for a comprehensive understanding of the microgel mechanical properties are not always implemented. Overall, the perspective is that current technologies have the capacity to provide detailed, nanoscopic mechanical characterization of microgels over an extended size range, to the high-throughput approaches providing distributions over the mechanical signatures, a feature not readily accessible by atomic force microscopy and micropipette aspiration.

Download Full-text