Jo Demeester

Polyelectrolyte microcapsules for biomedical applications

In this paper we review the recent contributions of polyelectrolyte microcapsules in the biomedical field, comprising in vitro and in vivodrug delivery as well as their applications as biosensors.

mRNA as gene therapeutic: how to control protein expression.

For many years, it was generally accepted that mRNA is too unstable to be efficiently used for gene therapy purposes. In the last decade, however, several research groups faced this challenge and not only proved the feasibility of mRNA-mediated transfection with surprising results regarding transfection efficiency and duration of protein expression, but also were able to demonstrate major advantages over the use of pDNA. These advantages will be the first issue discussed in this review, which first of all addresses the notions that mRNA does not need to cross the nuclear barrier to exert its biological activity and in addition lacks CpG motifs, which reduces its immunogenicity. Secondly, it provides insight in the (in)stability of the mRNA molecule, in how mRNA can be modified to increase its half-life and in the necessities of exogenously produced mRNA to be successfully used in transfection protocols. Furthermore, this review gives an in-depth overview of the different techniques and vehicles for intracellular mRNA delivery exploited by us and other groups, comprising electroporation, gene gun injection, lipo- and polyplexes. Finally, it covers recent literature describing specific applications for mRNA based gene delivery, showing that until now most attention has been paid to vaccination strategies. This review offers a comprehensive overview of current knowledge of the major theoretical as well as practical aspects of mRNA-mediated transfection, showing both its possibilities and its pitfalls and should therefore be useful for a diverse scientific audience.

Particulate vaccines: on the quest for optimal delivery and immune response.

Subunit vaccines offer a safer alternative to traditional organism-based vaccines, but their immunogenicity is impaired. This hurdle might be overcome by the use of micro- and nanodelivery systems carrying the antigen(s). This review discusses the rationale for the use of particulate vaccines and provides an overview of antigen-delivery vehicles currently under investigation. It further highlights the cellular uptake, antigen processing and the presentation by antigen-presenting cells because these processes are partially governed by particle characteristics and eventually determine the immunological outcome. Finally, we address the attractive concept of concomitant delivery of antigens and immunopotentiators. The condensed knowledge could be an asset for rationally designing antigen-delivery vehicles to obtain safe and efficacious vaccines.

Polyelectrolyte Microcapsules as Antigen Delivery Vehicles To Dendritic Cells: Uptake, Processing, and Cross‐Presentation of Encapsulated Antigens

Degradable polyelectrolyte microcapsules (PMs; see picture) as antigen delivery vehicles are taken up by dendritic cells (DCs) by macropinocytosis. Following uptake, the shell of the microcapsules ruptures, resulting in the invasion of the capsules by the cellular cytoplasm, thus allowing DCs to efficiently process encapsulated antigen.

Stimuli-responsive electrospun fibers and their applications

Stimuli-responsive electrospun nanofibers are gaining considerable attention as highly versatile tools which offer great potential in the biomedical field. In this critical review, an overview is given on recent advances made in the development and application of stimuli-responsive fibers. The specific features of these electrospun fibers are highlighted and discussed in view of the properties required for the diverse applications. Furthermore, several novel biomedical applications are discussed and the respective advantages and shortcomings inherent to stimuli-responsive electrospun fibers are addressed (136 references).

Sizing Nanomatter in Biological Fluids by Fluorescence Single Particle Tracking

Accurate sizing of nanoparticles in biological media is important for drug delivery and biomedical imaging applications since size directly influences the nanoparticle processing and nanotoxicity in vivo. Using fluorescence single particle tracking we have succeeded for the first time in following the aggregation of drug delivery nanoparticles in real time in undiluted whole blood. We demonstrate that, by using a suitable surface functionalization, nanoparticle aggregation in the blood circulation is prevented to a large extent.

Lipid and polymer nanoparticles for drug delivery to bacterial biofilms.

Biofilms are matrix-enclosed communities of bacteria that show increased antibiotic resistance and the capability to evade the immune system. They can cause recalcitrant infections which cannot be cured with classical antibiotic therapy. Drug delivery by lipid or polymer nanoparticles is considered a promising strategy for overcoming biofilm resistance. These particles are able to improve the delivery of antibiotics to the bacterial cells, thereby increasing the efficacy of the treatment. In this review we give an overview of the types of polymer and lipid nanoparticles that have been developed for this purpose. The antimicrobial activity of nanoparticle encapsulated antibiotics compared to the activity of the free antibiotic is discussed in detail. In addition, targeting and triggered drug release strategies to further improve the antimicrobial activity are reviewed. Finally, ample attention is given to advanced microscopy methods that shed light on the behavior of nanoparticles inside biofilms, allowing further optimization of the nanoformulations. Lipid and polymer nanoparticles were found to increase the antimicrobial efficacy in many cases. Strategies such as the use of fusogenic liposomes, targeting of the nanoparticles and triggered release of the antimicrobial agent ensured the delivery of the antimicrobial agent in close proximity of the bacterial cells, maximizing the exposure of the biofilm to the antimicrobial agent. The majority of the discussed papers still present data on the in vitro anti-biofilm activity of nanoformulations, indicating that there is an urgent need for more in vivo studies in this field.

Exploiting intrinsic nanoparticle toxicity: the pros and cons of nanoparticle-induced autophagy in biomedical research.

Nanoparticle-Induced Autophagy in Biomedical Research Karen Peynshaert,†,‡ Bella B. Manshian, Freya Joris,†,‡ Kevin Braeckmans,†,‡ Stefaan C. De Smedt,*,†,∥ Jo Demeester,† and Stefaan J. Soenen*,†,§ †Lab of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, ‡Centre for Nanoand Biophotonics, and Ghent Research Group on Nanomedicine, Ghent University, B9000 Ghent, Belgium Biomedical MRI Unit/MoSAIC, Department of Imaging and Pathology, Faculty of Medicine, Catholic University of Leuven, B3000 Leuven, Belgium

On the cellular processing of non-viral nanomedicines for nucleic acid delivery: Mechanisms and methods

In the field of nanomedicine, ample attention has been paid to the development of nanocarriers for the intracellular delivery of therapeutic cargo, such as nucleic acids for gene therapy. The efficiency with which these non-viral carriers deliver their payload at the required intracellular site of action remains low. Despite extensive research on cellular attachment, endocytosis and intracellular trafficking of nanocarriers, clear-cut rules for the design of effective nanocarriers to improve nucleic acid transfer are still lacking. This is mainly caused by the cell type-dependence of this highly dynamic cellular processing, and to the lack of reliable methods to study these events. For these reasons there is a strong demand for the development and standardization of such methods in order to better understand the intracellular dynamics of nanomedicine processing and validate cellular and intracellular targeting strategies. This review aims at providing an overview of the different processes that are currently known to be involved in the cellular processing of nanomedicines, with a focus on cellular internalization mechanisms, as this has received a great deal of attention in the last couple of years. Furthermore, the intracellular hurdles that need to be overcome to allow efficient NA transfer will be critically discussed. In addition, an overview will be given of various methodologies that have been applied to unravel these cellular processing mechanisms, with a discussion on their strengths and weaknesses.

Electrospun cellulose acetate phthalate fibers for semen induced anti-HIV vaginal drug delivery

Despite many advances in modern medicine, human immunodeficiency virus (HIV) still affects the health of millions of people world-wide and much effort is put in developing methods to either prevent infection or to eradicate the virus after infection has occurred. Here, we describe the potential use of electrospun cellulose acetate phthalate (CAP) fibers as a tool to prevent HIV transmission. During the electrospinning process, anti-viral drugs can easily be incorporated in CAP fibers. Interestingly, as a result of the pH-dependent solubility of CAP, the fibers are stable in vaginal fluid (the healthy vaginal flora has a pH of below 4.5), whereas the addition of small amounts of human semen (pH between 7.4 and 8.4) immediately dissolves the fibers which results in the release of the encapsulated drugs. The pH-dependent release properties have been carefully studied and we show that the released anti-viral drugs, together with the CAP which has been reported to have intrinsic antimicrobial activity, efficiently neutralize HIV in vitro.