A continuum model for a red blood cell transformation: sphere to crenated sphere

Engineering Photo-Crosslinked Antimicrobial Coating to Tackle Catheter-Associated Infections In Vivo

Microbial colonization on urinary and intravascular catheter surfaces results in steeply rising cases of catheter-associated infections as well as blood stream infections. Currently marketed efforts include impregnation and loading of antimicrobials and antiseptics that leach out into the local environment and inactivate microbes. However, they suffer from uncontrolled release, induction of resistance, and undesired toxicity. Here, in this manuscript, we have developed a photocurable, covalent coating on catheters using quaternary benzophenone-based amide (QSM-1). The coating was found to be active against drug-resistant bacteria and fungi. The coating inactivated stationary and persister cells of superbug MRSA and inhibited the formation of biofilms with retained activity against broad-spectrum bacteria when challenged in realistic urinary conditions. The coating was seen to be biocompatible in vitro and in vivo. Remarkably, the coated catheters showed reduced fouling and >99.9% reduction in bacterial burden when implanted in vivo in a mice model of subcutaneous implantation. We conceive the possibility of application of QSM-1-coated catheters in the healthcare settings to tackle the notorious catheter-associated nosocomial infections.

Echinocyte shapes: bending, stretching, and shear determine spicule shape and spacing

We study the shapes of human red blood cells using continuum mechanics. In particular, we model the crenated, echinocytic shapes and show how they may arise from a competition between the bending energy of the plasma membrane and the stretching/shear elastic energies of the membrane skeleton. In contrast to earlier work, we calculate spicule shapes exactly by solving the equations of continuum mechanics subject to appropriate boundary conditions. A simple scaling analysis of this competition reveals an elastic length Lambda(el), which sets the length scale for the spicules and is, thus, related to the number of spicules experimentally observed on the fully developed echinocyte.

Stability of spiculated red blood cells induced by intercalation of amphiphiles in cell membrane

The stability of spiculated red blood cells, induced by intercalation of amphiphilic molecules into the cell membrane, is studied. It is assumed that the stable red blood cell shape corresponds to the minimum of its membrane elastic energy, which consists of the local and non-local bilayer bending energies and of the skeleton shear elastic energy. The cell, volume and the membrane area are kept constant. It is calculated that the number of spicules of the stable echinocytic shape is larger when the amphiphile concentration is higher, which is in agreement with experimental observations. Also, it is established that, in explaining the stability of the echinocytic shape of the red blood cell, it is necessary to include the membrane skeleton shear elasticity.

A possible mechanism determining the stability of spiculated red blood cells

In this work the stability of spiculated red blood cells, called echinocytes, is studied. It is assumed that the stable echinocyte shape corresponds to the minimum of its membrane elastic energy. It is shown that if the membrane skeleton shear elasticity is not taken into account the calculated stable echinocyte shapes always have only one spicule. However, by considering the skeleton shear elastic energy also, the calculated stable echinocyte shapes have many spicula in agreement with experimental observations.

Vesicle formation in the Golgi apparatus

In this paper we examine the mechanics of vesicle budding from the Golgi apparatus. We propose a model for this process based on the notion that molecular surfactants can release the elastic energy stored in the lipid bilayer. The same physical process may drive other vesiculation processes, including coated vesicle formation and budding of enveloped viruses from the plasma membrane.