Sensing surface PEGylation with microcantilevers

Abstract

SummaryPolymers are often used to modify surface properties to control interfacial processes. Their sensitivity to solvent conditions and ability to undergo conformational transitions makes polymers attractive in tailoring surface properties with specific functionalities leading to applications in diverse areas ranging from tribology to colloidal stability and medicine. A key example is polyethylene glycol (PEG), which is widely used as a protein-resistant coating given its low toxicity and biocompatibility. We report here a microcantilever-based sensor for the in situ characterization of PEG monolayer formation on Au using the “grafting to” approach. Moreover, we demonstrate how microcantilevers can be used to monitor conformational changes in the grafted PEG layer in different solvent conditions. This is supported by atomic force microscope (AFM) images and force–distance curve measurements of the microcantilever chip surface, which show that the grafted PEG undergoes a reversible collapse when switching between good and poor solvent conditions, respectively.

Sensitivity and Limit of Detection of biosensors based on ring resonators

“…In the case of the solution with Aflatoxin, the drift is more pronounced in the first minutes of the injection, and then slowly decreases until reaching, in the last minutes, a slope similar to the one of the sample without toxin. Such behaviour can indicate a binding of the Aflatoxin to the aptamer, as the adsorption of surface-active molecules at the interface of a two-phase system can be modelled with the classical Langmuir isotherm, which describes an exponential binding profile [12].…”

Cantilevers for biological monitoring: opportunities for classical and quantum physics

“…If the change of surface stress occurs on the cantilever's upper side, then a downward bending caused by an increased surface area is referred to as compressive stress, whilst an upward bending induced by a decreased surface area is tensile surface stress [22,23]. One of the most common methods for biological monitoring is the surface stress principle, which is further exemplified with various applications in Section 3.…”

“…Kappeler two decades of investigations by various groups, there is no complete theoretical model describing the origins of the surface stress generated from a molecular binding event and how this translates into the mechanical deformation of the cantilever [13,[22][23][24]. As a result, complete understanding of the origin of surface stress is much sought after, as it is expected to enhance cantilever sensors' sensitivity and specificity.…”

“…This bimetallic thermal effect allows accurate monitoring of temperature changes for microcalorimeter and photothermal applications [24,25]. Furthermore, it can also be used for calibration of the cantilever sensor's optical read-out system, which will be described in Section 2.3 [22].…”

Optimization of PEGylated nanoemulsions for improved pharmacokinetics of BCS class II compounds

“…With increase in chain length and density, the PEG chains form brush-like configuration which restricts the mobility of the PEG chains. To achieve improved stealth characteristics, between mushroom and brush-like configuration is necessary which increases the flexibility of most of the chains and optimal density which provides complete surface coverage to prevent binding of opsonin proteins (Owen & Peppas, 2006;Backmann et al, 2010;Wang & Thanou, 2010). Danazol, a synthetic steroid drug was considered water-insoluble because its solubility in water was reported to be 0.59 mg/mL (Erlich et al, 1999) and was used as a model compound.…”