Biophysical studies on collagen-lipid interaction

Size-tunable lipid vectors for controlled local delivery of siRNA from gene activated matrix

Tissue engineering aims to restore or replace different types of biological tissues through the association of cells, biologic factors and biomaterials. Currently, stem cells arise as a major cell source for many therapeutic indications, and their association with 3D scaffolds allow increasing regenerative medicine efficiency. In this context, the use of RNA interference to enhance or control stem cell differentiation into the desired phenotype appears as a promising strategy. However, achieving high transfection efficiency of cells in a 3D structure requires the use of a vector allowing for the spatiotemporally controlled release of the genetic material from these scaffolds. In this study, we report a new siRNA nanovector, called solvent exchange lipoplexe formulation (SELF), which has a tunable size, is stable over time in cell culture conditions and possess a high efficiency to transfect primary human mesenchymal stromal cells (hMSC). We associated SELFs with porous 3D collagen microspheres and demonstrated that the loading capacity and release kinetics were different depending on the size of the associated SELF. Interestingly, these different release profiles resulted in differences in the transfection kinetics of hMSCs. This original and unique type of gene activated matrix, with adaptable release kinetics, could be of interest for long-term and/or sequential transfection profiles of stem cells in 3D culture. STATEMENT OF SIGNIFICANCE: This work combines the use of human mesenchymal stromal cell (hMSC) and gene therapy for tissue engineering. Here, a gene-activated matrix was elaborated with collagen microspheres supporting hMSCs and acting as a reservoir for transfection vectors. This injectable GAM allows for the local and sustained delivery of nucleic acids, hence long-lasting transfection of the supported cells. With the original synthesis protocol presented herein, the size of the nanocarriers can be easily adapted, resulting in different siRNA release profiles from the microspheres. Most interestingly, different siRNA release profiles gave rise to different cell transfection profiles as assessed by the downregulation of a target gene. This highlights the versatility of the system and its suitability for various pathophysiological needs in regenerative medicine.

Investigation of the Structural Mechanism and Film Growth on Cytoprotective Type I Collagen-Based Nanocoating of Individual Cellular Surfaces

Cell surface coating using the layer-by-layer assembly (LbL) method has many advantages for biomedical applications. Because the cell surface is a dynamic and highly complex structure, it is hypothesized that LbL multilayer films on cells have characteristics different from those observed in traditional film characterization results. Here, to demonstrate the mechanism of LbL-film formation on cells, LbL films are prepared on HeLa cells using collagen (Col) and hyaluronic acid (HA). The growth behavior of the film and the main driving forces inducing the formation of an LbL film on the cells are investigated. Col self-assembles via electrostatic and hydrophobic interactions; therefore, the Col-based film on the cells grows laterally rather than volumetrically. For the film construction conditions, the ionic density and chain conformation of the polymers change, resulting in mainly hydrophobic interactions. Additional interactions, such as hydrophobic interactions and biological recognition between the substrate and building blocks, also exist and tightly stabilize the films on the cells. The Col/HA film shows an even distribution on the cell surface as the extracellular matrix, and it activates proliferation and the cytoprotective signaling pathway under harsh conditions, resulting in the focal adhesion kinase signaling pathway and low lactate dehydrogenase release. Therefore, information for film construction on cells is beneficial to understand the effectiveness of an LbL film for cells.

Bioengineered liposome-scaffold composites as therapeutic delivery systems

The therapeutic potential of liposomes can be amplified when combined with biomaterial scaffolds. Such configurations overcome the convergent demands of therapies by enabling enhanced delivery, environmental responsiveness and potency. Liposomes benefit from the increased physical and mechanical strength, favorable rheological properties and natural environment conducive to improved tissue formation that scaffolds provide, while enabling biocompatible delivery of hydrophilic and lipophilic compounds that can be further functionalized to achieve targeted delivery. Topical, ocular, oral, nasal and vaginal applications have been explored using various polymer- or nanofiber-based scaffolds. Mechanistic and rheological findings on complexation between biomaterials, liposomes and cargo have led to multimodal systems with tremendous clinical potential. A review of the key developments in bioengineered liposome-scaffold composites is presented in this manuscript.

Ehrlich tumor inhibition using doxorubicin containing liposomes

Ehrlich tumors were grown in female balb mice by subcutaneous injection of Ehrlich ascites carcinoma cells. Mice bearing Ehrlich tumor were injected with saline, DOX in solution or DOX encapsulated within liposomes prepared from DMPC/CHOL/DPPG/PEG-PE (100:100:60:4) in molar ratio. Cytotoxicity assay showed that the IC50 of liposomes containing DOX was greater than that DOX only. Tumor growth inhibition curves in terms of mean tumor size (cm(3)) were presented. All the DOX formulations were effective in preventing tumor growth compared to saline. Treatment with DOX loaded liposomes displayed a pronounced inhibition in tumor growth than treatment with DOX only. Histopathological examination of the entire tumor sections for the various groups revealed marked differences in cellular features accompanied by varying degrees in necrosis percentage ranging from 12% for saline treated mice to 70% for DOX loaded liposome treated mice. The proposed liposomal formulation can efficiently deliver the drug into the tumor cells by endocytosis (or passive diffusion) and lead to a high concentration of DOX in the tumor cells. The study showed that the formulation of liposomal doxorubicin improved the therapeutic index of DOX and had increased anti-tumor activity against Ehrlich tumor models.

Effect of size at the nanoscale and bilayer rigidity on skin diffusion of liposomes

This study reports the effect of liposome particle size at the nanoscale and bilayer deformability on the permeation through MatTek human skin equivalents and provides a comparative quantitative measure through calculation of diffusion coefficients. Exploring DOPC and DPPC fluorescent liposomes, our results demonstrate the faster diffusion of 50 nm liposomes compared with 100 and 200 nm liposomes when the lipid bilayer remains the same. Diffusion kinetics of the 50 nm particles appear not to depend on the rigidity of the lipid layer, whereas diffusion of particles larger than 100 nm is significantly affected by the rigidity of the bilayer, and DOPC liposomes diffuse faster than their DDPC equivalents. Our results suggest that liposomes composed of a rigid bilayer can be expected to remain intact after passing through the stratum corneum.

A review on applications of liposomes in textile processing

This review discusses the properties of liposomes and their role in the textile process, including textile preparation and dyeing. Liposomes have a surface activity effect due to a hydrophilic head group and hydrophobic hydrocarbon tail. Its preparations do not tend to foam, which advantageously distinguishes them from other textile auxiliaries. According to the carrier role of liposomes, they can be used in several textile processes such as textile finishing and dyeing with several types of dyes and fibers. Each application is discussed in this review paper. Several types of dyes are encapsulated by liposomes in the dyeing process and their presence indicates that they have retardant and leveling effects according to their gradual release of dyes. In addition, the presence of liposomes in the textile process can improve the mechanical properties of textile products, resulting in better wash fastness properties and leveling effect and handle properties. The best character of liposomes is a reduction in temperature of process resulting to save energy and they are environment degradable materials.