Characterization of nucleic acid molecule/liposome complexes and rheological effects on pluronic/alginate matrices

Gelation Behaviour of Pluronic F127/Polysaccharide Systems Revealed via Thioflavin T Fluorescence

Fast, reliable methods for characterizing the micelle-to-gel transition in emerging Pluronic F127/polysaccharide materials are essential for tailoring their applications as in situ gelling delivery systems. This study describes a simple fluorimetric method based on the response to gelation of the molecular probe thioflavin T (ThT). The techniques employed are (second derivative) steady-state and synchronous fluorescence. The capabilities of ThT as gelation reporter are tested for three model systems: Pluronic F127 (P16.6%), Pluronic F127/alginate (P16.6%ALG2%) and Pluronic F127/hyaluronic acid (P16.6%HA0.5%). We demonstrate that the changes in the short and long wavelength emissions of ThT allow accurate determination of the critical gelation temperatures in the investigated systems. The spectroscopic data providing information at molecular level are complemented with differential scanning microcalorimetric results revealing additional macroscopic insight into the micellization process. The gelation study is preceded by a solvatochromic analysis of ThT.

Dual Action Nitric Oxide and Fluoride Ion-Releasing Hydrogels for Combating Dental Caries

Demineralization and breakdown of tooth enamel are characterized by a condition called dental caries or tooth decay, which is caused by two main factors: (1) highly acidic food intake without proper oral hygiene and (2) overactive oral bacteria generating acidic metabolic byproducts. Fluoride treatments have been shown to help rebuild the hydroxyapatite structures that make up 98% of enamel but do not tackle the bacterial overload that continues to threaten future demineralization. Herein, we have created a dual-function Pluronic F127-alginate hydrogel with nitric oxide (NO)- and fluoride-releasing capabilities for the two-pronged treatment of dental caries. Analysis of the hydrogels demonstrated porous, shear-thinning behaviors with tunable mechanical properties. Varying the weight percent of the NO donor S-nitrosoglutathione (GSNO) within the hydrogel enabled physiologically actionable NO release over 4 h, with the fabricated gels demonstrating storage stability over 21 days. This NO-releasing capability resulted in a 97.59% reduction of viable Streptococcus mutans in the planktonic state over 4 h and reduced the preformed biofilm mass by 48.8% after 24 h. Delivery of fluoride ions was confirmed by a fluoride-sensitive electrode, with release levels resulting in the significant prevention of demineralization of hydroxyapatite discs after treatment with an acidic demineralization solution. Exposure to human gingival fibroblasts and human osteoblasts showed cytocompatibility of the hydrogel, demonstrating the potential for the successful treatment of dental caries in patients.

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.

Recent advances in smart biotechnology: Hydrogels and nanocarriers for tailored bioactive molecules depot

Over the past ten years, the global biopharmaceutical market has remarkably grown, with ten over the top twenty worldwide high performance medical treatment sales being biologics. Thus, biotech R&D (research and development) sector is becoming a key leading branch, with expanding revenues. Biotechnology offers considerable advantages compared to traditional therapeutic approaches, such as reducing side effects, specific treatments, higher patient compliance and therefore more effective treatments leading to lower healthcare costs. Within this sector, smart nanotechnology and colloidal self-assembling systems represent pivotal tools able to modulate the delivery of therapeutics. A comprehensive understanding of the processes involved in the self-assembly of the colloidal structures discussed therein is essential for the development of relevant biomedical applications. In this review we report the most promising and best performing platforms for specific classes of bioactive molecules and related target, spanning from siRNAs, gene/plasmids, proteins/growth factors, small synthetic therapeutics and bioimaging probes.

Potential Applications of Nanocellulose-Containing Materials in the Biomedical Field

Because of its high biocompatibility, bio-degradability, low-cost and easy availability, cellulose finds application in disparate areas of research. Here we focus our attention on the most recent and attractive potential applications of cellulose in the biomedical field. We first describe the chemical/structural composition of cellulose fibers, the cellulose sources/features and cellulose chemical modifications employed to improve its properties. We then move to the description of cellulose potential applications in biomedicine. In this field, cellulose is most considered in recent research in the form of nano-sized particle, i.e., nanofiber cellulose (NFC) or cellulose nanocrystal (CNC). NFC is obtained from cellulose via chemical and mechanical methods. CNC can be obtained from macroscopic or microscopic forms of cellulose following strong acid hydrolysis. NFC and CNC are used for several reasons including the mechanical properties, the extended surface area and the low toxicity. Here we present some potential applications of nano-sized cellulose in the fields of wound healing, bone-cartilage regeneration, dental application and different human diseases including cancer. To witness the close proximity of nano-sized cellulose to the practical biomedical use, examples of recent clinical trials are also reported. Altogether, the described examples strongly support the enormous application potential of nano-sized cellulose in the biomedical field.

Development of a simple, biocompatible and cost-effective Inulin-Diethylenetriamine based siRNA delivery system

Small interfering RNAs (siRNAs) have the potential to be of therapeutic value for many human diseases. So far, however, a serious obstacle to their therapeutic use is represented by the absence of appropriate delivery systems able to protect them from degradation and to allow an efficient cellular uptake. In this work we developed a siRNA delivery system based on inulin (Inu), an abundant and natural polysaccharide. Inu was functionalized via the conjugation with diethylenetriamine (DETA) residues to form the complex Inu-DETA. We studied the size, surface charge and the shape of the Inu-DETA/siRNA complexes; additionally, the cytotoxicity, the silencing efficacy and the cell uptake-mechanisms were studied in the human bronchial epithelial cells (16HBE) and in the hepatocellular carcinoma derived cells (JHH6). The results presented here indicate that Inu-DETA copolymers can effectively bind siRNAs, are highly cytocompatible and, in JHH6, can effectively deliver functional siRNAs. Optimal delivery is observed using a weight ratio Inu-DETA/siRNA of 4 that corresponds to polyplexes with an average size of 600nm and a slightly negative surface charge. Moreover, the uptake and trafficking mechanisms, mainly based on micropinocytosis and clatrin mediated endocytosis, allow the homogeneous diffusion of siRNA within the cytoplasm of JHH6. Notably, in 16 HBE where the trafficking mechanism (caveolae mediated endocytosis) does not allow an even distribution of siRNA within the cell cytoplasm, no significant siRNA activity is observed. In conclusion, we developed a novel inulin-based siRNA delivery system able to efficiently release siRNA in JHH6 with negligible cytotoxicity thus opening the way for further testing in more complex in vivo models.

Physical characterization of alginate-Pluronic F127 gel for endoluminal NABDs delivery

Here we focus the attention on the physical characteristics of a highly biocompatible hydrogel made up of crosslinked alginate and Pluronic F127 (PF127). This is a composite polymeric blend we propose for artery endoluminal delivery of an emerging class of molecules named nucleic acid based drugs (NABDs). The physical characterization of our composite gel, i.e. mesh size distribution and PF127-alginate mutual organization after crosslinking, can significantly determine the NABDs release kinetics. Thus, to explore these aspects, different technical approaches, i.e. rheology, low/high field NMR and TEM, were used. While rheology provided information at the macroscopic and nano-level, the other three approaches gave details at the nano-level. We observe that Pluronic micelles, organizing in cubic ordered domains, generate, upon alginate crosslinking, the formation of meshes (≈ 150 nm) larger than those occurring in a Pluronic-free alginate network (≈ 25 nm). Nevertheless, smaller alginate meshes are still on and can just host un-structured Pluronic micelles and water. Accordingly, the gel structure is quite inhomogeneous, where big meshes (filled by crystalline Pluronic) co-exist with smaller meshes (hosting water and un-structured PF127 micelles). While big meshes offer a considerable hindering action on a diffusing solute, smaller ones represent a sort of free space where solute diffusion is faster. The presence of big and small meshes indicates that drug release may follow a double kinetics characterized by a fast and slow release. Notably, this behavior is considered appropriate for endoluminal drug release to the arterial wall.

Alginate/PEO-PPO-PEO composite hydrogels with thermally-active plasticity

Stimuli-responsive hydrogels with high strength and toughness have received significant interest in recent years. Here, we report thermally active composite hydrogels comprising alginate and one of two poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers. Temperature-sensitive structural and mechanical changes are probed using calorimetry, neutron scattering, shear rheology, unconfined compression, and fracture. Below the lower gelation temperature, LGT, the mechanical properties are dominated by alginate. As the LGT is reached, the contribution of PEO-PPO-PEO to the mechanical properties is activated, resulting in order-of-magnitude increases in elastic modulus. Under compression, we show the evolution of plasticity for the composite hydrogels as the LGT is approached and surpassed, resulting in dramatic increases in fracture stress compared to neat alginate hydrogels. Plasticity was observed above the LGT and may be attributed to restructuring from the sliding of packed micelles and strain-hardening due to stress concentration on alginate cross-links and junction zones, ultimately leading to fracture.

Role of E2F1-cyclin E1-cyclin E2 circuit in human coronary smooth muscle cell proliferation and therapeutic potential of its downregulation by siRNAs

Aberrant coronary vascular smooth muscle cell (CSMC) proliferation is a pivotal event underlying intimal hyperplasia, a phenomenon impairing the long-term efficacy of bypass surgery and angioplasty procedures. Consequently research has become focused on efforts to identify molecules that are able to control CSMC proliferation. We investigated downregulation of CSMC growth by small interfering RNAs (siRNAs) targeted against E2F1, cyclin E1, and cyclin E2 genes, whose contribution to CSMC proliferation is only now being recognized. Chemically synthesized siRNAs were delivered by two different transfection reagents to asynchronous and synchronous growing human CSMCs cultivated either in normo- or hyperglycemic conditions. The depletion of each of the three target genes affected the expression of the other two genes, demonstrating a close regulatory control. The clearest effects associated with the inhibition of the E2F1-cyclin E1/E2 circuit were the reduction in the phosphorylation levels of the retinoblastoma protein pRB and a decrease in the amount of cyclin A2. At the phenotypic level the downmodulation of CSMC proliferation resulted in a decrease of S phase matched by an increase of G1-G0 phase cell amounts. The antiproliferative effect was cell-donor and transfectant independent, reversible, and effective in asynchronous and synchronous growing CSMCs. Importantly, it was also evident in hyperglycemia, a condition that underlies diabetes. No significant aspecific cytotoxicity was observed. Our data demonstrate the interrelation among E2F1-cyclin E1-cyclin E2 and the pivotal role this circuit exerts in CSMC proliferation. Additionally, our work validates the concept of utilizing anti-E2F1-cyclin E1-cyclin E2 siRNAs to develop a potential novel therapy to control intimal hyperplasia.

Mathematical modelling of NABD release from endoluminal gel paved stent

Coronary restenosis consists of the partial/total re-occlusion of the artery lumen following percutaneous transluminal angioplasty (PTCA). In order to match this pathology, PTCA is followed by the implantation of rigid scaffolds (stent or coated stent) aimed to contrast the most important mechanical (coronary wall elastic recoil and late remodelling) and biological (smooth muscle cells iper-proliferation) factors leading to restenosis. In the light of the clinical problems recently arisen about the use of traditional coated stents, this paper proposes a theoretical study to comprehend the release kinetics of novel anti-proliferative drugs, i.e. nucleic acid based drugs (NABD), complexed with the proper delivery agent (DA). The release of NABD-DA is supposed to occur from a double gel layer adhering to coronary wall and embedding the stent. The proposed mathematical model assumes that diffusion, convection and cellular internalisation/metabolism are the leading mechanisms ruling drug spreading in the coronary wall. In addition, stent void fraction, positioning (totally embedded or totally out of the coronary wall) and continuous or discontinuous character of the gel layer are other three important model parameters. In order to generalise the results, stent geometry is idealised as a series of not connected, equally spaced, rings positioned in the stented zone. In correspondence of stent strut, drug transport cannot occur. The most important outcomes of this study are that, in the usual void fraction range (0.7-0.9), stent presence does not sensibly affect NABD-DA release kinetics. In addition, whereas stent positioning in the continuous gel configuration (totally embedded or totally out of coronary wall) is not very important, in the discontinuous case, it becomes relevant. Finally, this study evidences that a proper mixture of NABD complexed with different (in dimensions and kind) DA can ensure an almost constant NABD coronary concentration for several months, as requested by clinical observations.