Baculovirus transit through insect cell membranes: A mechanistic approach.

Baculovirus systems are used for various purposes, but the kinetics of the infection process is not fully understood yet. We investigated the dynamics of virion movement from a medium toward the interior of insect cells and established a mechanistic model that shows an excellent fit to experimental results. It also makes possible a description of the viral dynamics on the cell surface. A novel measurement method was used to distinguish between infected cells that carry virions on their surfaces, cells that carry virions in their interior, and those carrying virions both inside and on their surface. The maximum number of virions carried by a cell: 55 viruses/cell, and the time required for viral internalization, 0.8 h , are reported. This information is particularly useful for assessing the infection efficacy and the required number of virions needed to infect a given cell population. Although our model specifically concerns the infection process of Sf9 insect cells by baculovirus, it describes general features of viral infection. Some of the model features may eventually be applicable in the studies towards palliation of the COVID-19 outbreak.

New doxorubicin nanoparticles engineered from calcium-crosslinked carbomer and a microemulsion precursor.

The purpose of this study was to investigate a new polymeric system and production process in which self-assembled doxorubicin-loaded nanoparticles were synthetized by using a water-in-oil microemulsion as a template and calcium ions as cross-linkers. The manufacturing process combined cross-linking of carbomer within a W/O microemulsion followed by a phase-separation technique to avoid using organic solvents for extraction. To assess the sustained release behavior of doxorubicin from the nanoparticles, we have developed a new simple method based on the permeability coefficient of a synthetic membrane mounted on Franz diffusion cell system. Franz cells were preferred over the commonly used dialysis tubing because they provide adequate measures of the diffusion area as well as the volumes of the media in both sides of the membrane. The lower permeability values obtained for nanoparticles have shown that the release is a limiting step of the diffusion process, while the calculated straight lines may imply that the apparent release rate of the nanoparticle ensembles is close to a zero-order kinetics. The new drug release method for the evaluation of nano-carriers, utilizing a simple linear model to determine the permeability coefficient, has been proposed for perfect sink and non-sink conditions.

Bubble growth within the skin by rectified diffusion might play a significant role in sonophoresis.

Low frequency ultrasound has successfully been used for enhancing transdermal transport of a variety of different molecules. This phenomenon is referred to as sonophoresis. Several attempts have been made to investigate the enhancing mechanism in order to modulate the overall process. In this study we assess whether rectified diffusion is a process that occurs within the skin, which could eventually lead to channeling and thereby to transdermal sonophoresis. The model presented in this paper is based on the following postulate: gas bubbles are randomly distributed within the lipid bilayers of the stratum corneum (SC). As the skin is subjected to ultrasound, gas bubbles grow by rectified diffusion. During this period, bubbles may merge with the outer or inner boundaries of the SC, or merge with neighboring bubbles. Eventually, channels are created, allowing drugs to easily penetrate through the most significant barrier to transdermal delivery, the SC. As a result, transdermal transport rate is enhanced. In this work, a mathematical model has been formulated, in which permeability enhancement of the SC is linked to channels, possibly created by means of rectified diffusion. Sonophoresis may result from various mechanisms that act in synergy. The present model predicts that rectified diffusion might be one of the factors that lead to sonophoresis during ultrasound treatment.

Harvesting Low Molecular Weight Biomarkers Using Gold Nanoparticles.

We developed and characterized a platform based on gold (Au) nanoparticles (NPs) coated with poly(acrylic acid) (PAA) for harvesting positively charged, low molecular weight (LMW) proteins. The particles are synthesized using a layer by layer (LbL) procedure: first the gold NPs are coated with positively charged polyethylenimine (PEI) and subsequently with PAA. This simple procedure produces stable PAA-PEI-Au (PPAu) NPs with high selectivity and specificity. PPAu NPs successfully harvested, separated, and detected various LMW proteins and peptides from serum containing a complex mixture of abundant high molecular weight (HMW) proteins, including bovine serum albumin (BSA) and Immunoglobulin G (IgG). In addition, PPAu NPs selectively harvested and separated LMW proteins from serum in the presence of another positively charged competing protein. Furthermore, PPAu NPs successfully harvested a LMW biomarker in a mock diseased state. This system can be applied in various biomedical applications where selective harvesting and identifying of LMW proteins is required. A particularly useful application for this system can be found in early cancer diagnosis as described hereinafter.

Ultrasound mediated transdermal drug delivery.

Transdermal drug delivery offers an attractive alternative to the conventional drug delivery methods of oral administration and injections. However, the stratum corneum serves as a barrier that limits the penetration of substances to the skin. Application of ultrasound (US) irradiation to the skin increases its permeability (sonophoresis) and enables the delivery of various substances into and through the skin. This review presents the main findings in the field of sonophoresis in transdermal drug delivery as well as transdermal monitoring and the mathematical models associated with this field. Particular attention is paid to the proposed enhancement mechanisms and future trends in the fields of cutaneous vaccination and gene therapy.

A mathematical model of drug release from liposomes by low frequency ultrasound.

Administration of drugs using small (<100 nm) unilamellar liposomes enables effective targeting of tumors and inflamed tissue. Therapeutic efficacy may be enhanced by triggering liposomal drug release in the desired organ in a controlled manner using a noninvasive external signal. Previous studies have demonstrated that low frequency ultrasound (LFUS) can be used to control the release of drugs from liposomes. LFUS irradiation has a twofold effect: (1) it causes the impermeable liposome membrane to become permeable and (2) it induces liposome disintegration. Immediately upon cessation of LFUS irradiation the membrane resumes its impermeable state and liposome disintegration stops. The mathematical model presented here is aimed at providing a better quantitative and qualitative understanding of LFUS-induced liposomal drug release, which is essential for safe and effective implementation of this technique. The time-dependent release patterns are determined by the liposome disintegration patterns and by two key parameters: (a) the average permeability of the membrane to the drug and (b) the ratio between the volume of the entire dispersion and the initial volume of all the liposomes in the dispersion. The present model implies that LFUS irradiation triggers two liposomal drug-release mechanisms: the predominant one is diffusion through the LFUS-compromised liposome membrane, and the less significant one is liposome disintegration.

A model of the dynamics of insect cell infection at low multiplicity of infection.

In the present paper, we offer a preliminary mathematical model that describes the dynamic process of cell infection with baculovirus at low multiplicity of infection (MOI). The model accounts for the chain of events that follow the infection of insect cells, namely the eclipse period, the budding of viral particles from those cells, their attachment to non-infected cells and the initiation of a new infection cycle. These cycles appear as fluctuations in the viral concentration of actual cell culture media. The potential of the present approach in simulating the in vitro production of biological insecticides is demonstrated. The influence of the shape of the virus-budding function is shown, and parameter sensitivity analysis is carried out. The model provides a quantitative tool for the analysis of this complex dynamic system.

Converging three-dimensional Stokes flow of two fluids in a T-type bifurcation.

Studies of three-dimensional Stokes flow of two Newtonian fluids that converge in a T-type bifurcation have important applications in polymer coextrusion, blood flow through the venous microcirculation, and other problems of science and technology. This flow problem is simulated numerically by means of the finite element method, and the solution demonstrates that the viscosity ratio between the two fluids critically affects flow behaviour. For the parameters investigated, we find that as the viscosity ratio between the side branch and the main branch increases, the interface between the merging fluids bulges away from the side branch. The viscosity ratio also affects the velocity distribution: at the outlet branch, the largest radial gradients of axial velocity appear in the less-viscous fluid. The distribution of wall shear stress is non-axisymmetric in the outlet branch and may be discontinuous at the interface between the fluids.