Wednesday, November 23, 2016
Wednesday, November 16, 2016
This theory note explains how the surface roughness influences on the contact angle and wettability of the substrate
Both chemical and topographical properties of the surface are important parameters in many different applications and processes, where wetting and adhesion behavior needs to be optimized. Wettability can be studied by measuring the contact angle of the substrate with the given liquid. The well-known Young equation describes the balance at the three-phase contact of solid, liquid and vapor
Monday, June 20, 2016
From tradition SPR to MP-SPR:
From measurements to understanding
Surface Plasmon Resonance (SPR) is an established method for
biomolecular interaction analysis. It is popular due to its sensitivity
as well as its capability to measure label-free and in real-time.
Multi-Parametric Surface Plasmon Resonance (MP-SPR) is based on
SPR principle, however its advantageous optical setup measures
a full SPR curve which enables new insight into interactions.
For instance, PureKinetics™ feature provides measurements of
small molecules, lipids and biomaterials without bulk effect.
MP-SPR widens the application range of traditional SPR from small
molecules up to nanoparticles and even living cells. Measurements
can be performed also in complex media such as serum.
Additionaly, MP-SPR provides information about layer properties.
Thickness and refractive index (RI) data can be utilized in material
characterization from Ångström thick layers up to micrometers
or to ensure conformation of the molecules on the surface.
Premium quality kinetic data with
Bulk effect (sometimes called DMSO effect, salt or solvent artifact) is
the difference in liquid composition between samples and running
buffer. The composition difference is seen as a change in refractive
index, which in turn appears as a shift in measured SPR curve.
In traditional SPR, imaging SPR or localized SPR, only part of the SPR
curve can be seen and therefore, several steps have to be taken in
order to separate true molecular binding from the undesired bulk
The unique optical setup of MP-SPR instruments enables
cross-correlation of parameters provided by the MP-SPR method
and allows simple in-line elimination of interfering bulk signal
using PureKinetics™ feature. This feature is available in all
MP-SPR Navi™ instruments.
Gold nanoparticles were immobilized on a monolayer selfassembled
on gold. Functional groups on the chain ends of the
monolayer facilitated an anchoring of gold nanoparticles to the
layer. Multi-Parametric Surface Plasmon Resonance (MP-SPR)
enabled a real-time measurement of the binding of the gold
nanoparticles to the surface layer.
Gold nanoparticles (AuNPs) exhibits interesting optical and electronic
properties that find application in sensors, catalysis, electronics,
photonics, solar cells, cancer diagnosis and therapy. Controlled attachment
of Au nanoparticles at a solid interface is required for many of
these applications. Although many methods have been developed to
fabricate Au nanoparticle assemblies, developing simple and effective
routes is still very attractive. Usually, the immobilization can be
performed using a covalent or an electrostatic interaction between
the nanoparticles and the substrate. In this study functional molecules
are used for linking gold nanoparticles to a solid surface. Molecules
possessing functional groups can be attached to the solid surface in
a controlled manner and permits nanoparticle immobilization.
Monolayers with functional groups assembled on a gold surface
can be used for coupling of gold nanoparticles. In this study MP-SPR
turned out to be a unique method for determining the deposition of
metal nanoparticles to the surface layer in real-time. AuNPs exhibit
strong surface plasmon resonances and even a large response could
be observed by MP-SPR when nanoparticles were interacting with
the surface layer. Functional groups on the chains ends enable
an anchoring of gold nanoparticles or even embedding into the
chains. MP-SPR is a unique tool for studying metal nanoparticles for
applications in sensors, electronics, photonics, solar cells or cancer
diagnosis and therapy.