Functionalized dendrimers as endotoxin sponges

The Bioactive Core and Corona Synergism of Quantized Gold Enables Slowed Inflammation and Increased Tissue Regeneration in Wound Hypoxia

The progress of wound regeneration relies on inflammation management, while neovascular angiogenesis is a critical aspect of wound healing. In this study, the bioactive core and corona synergism of quantized gold (QG) were developed to simultaneously address these complicated issues, combining the abilities to eliminate endotoxins and provide oxygen. The QG was constructed from ultrasmall nanogold and a loosely packed amine-based corona via a simple process, but it could nonetheless eliminate endotoxins (a vital factor in inflammation also called lipopolysaccharides) and provide oxygen in situ for the remodeling of wound sites. Even while capturing endotoxins through electrostatic interactions, the catalytic active sites inside the nanogold could maintain its surface accessibility to automatically transform the overexpressed hydrogen peroxide in hypoxic wound regions into oxygen. Since the inflammatory stage is an essential stage of wound healing, the provision of endotoxin clearance by the outer organic corona of the QG could slow inflammation in a way that subsequently promoted two other important stages of wound bed healing, namely proliferation and remodeling. Relatedly, the efficacy of two forms of the QG, a liquid form and a dressing form, was demonstrated at wound sites in this study, with both forms promoting the development of granulation, including angiogenesis and collagen deposition. Thus, the simply fabricated dual function nanocomposite presented herein not only offers reduced batch-to-batch variation but also increased options for homecare treatments.

Assessment of interactions of efavirenz solid drug nanoparticles with human immunological and haematological systems

Background

Recent work has developed solid drug nanoparticles (SDNs) of efavirenz that have been demonstrated, preclinically, improved oral bioavailability and the potential to enable up to a 50% dose reduction, and is currently being studied in a healthy volunteer clinical trial. Other SDN formulations are being studied for parenteral administration, either as intramuscular long-acting formulations, or for direct administration intravenously. The interaction of nanoparticles with the immunological and haematological systems can be a major barrier to successful translation but has been understudied for SDN formulations. Here we have conducted a preclinical evaluation of efavirenz SDN to assess their potential interaction with these systems. Platelet aggregation and activation, plasma coagulation, haemolysis, complement activation, T cell functionality and phenotype, monocyte derived macrophage functionality, and NK cell function were assessed in primary healthy volunteer samples treated with either aqueous efavirenz or efavirenz SDN.

Results

Efavirenz SDNs were shown not to interfere with any of the systems studied in terms of immunostimulation nor immunosuppression. Although efavirenz aqueous solution was shown to cause significant haemolysis ex vivo, efavirenz SDNs did not. No other interaction with haematological systems was observed. Efavirenz SDNs have been demonstrated to be immunologically and haematologically inert in the utilised assays.

Conclusions

Taken collectively, along with the recent observation that lopinavir SDN formulations did not impact immunological responses, these data indicate that this type of nanoformulation does not elicit immunological consequences seen with other types of nanomaterial. The methodologies presented here provide a framework for pre-emptive preclinical characterisation of nanoparticle safety.

Electronic supplementary material

The online version of this article (10.1186/s12951-018-0349-y) contains supplementary material, which is available to authorized users.

Invited review: Mechanisms of endotoxin neutralization by synthetic cationic compounds

A basic challenge in the treatment of septic patients in critical care units is the release of bacterial pathogenicity factors such as lipopolysaccharide (LPS, endotoxin) from the cell envelope of Gram-negative bacteria due to killing by antibiotics. LPS aggregates may interact with serum and membrane proteins such as LBP (lipopolysaccharide-binding protein) and CD14 leading to the observed strong reaction of the immune system. Thus, an effective treatment of patients infected by Gram-negative bacteria must comprise beside bacterial killing the neutralization of endotoxins. Here, data are summarized for synthetic compounds indicating the stepwise development to very effective LPS-neutralizing agents. These data include synthetic peptides, based on the endotoxin-binding domains of natural binding proteins such as lactoferrin, Limulus anti-LPS factor, NK-lysin, and cathelicidins or based on LPS sequestering polyamines. Many of these compounds could be shown to act not only in vitro, but also in vivo (e.g . in animal models of sepsis), and might be useful in future clinical trials and in sepsis therapy.

Predicting Adsorption Affinities of Small Molecules on Carbon Nanotubes Using Molecular Dynamics Simulation

Computational techniques have the potential to accelerate the design and optimization of nanomaterials for applications such as drug delivery and contaminant removal; however, the success of such techniques requires reliable models of nanomaterial surfaces as well as accurate descriptions of their interactions with relevant solutes. In the present work, we evaluate the ability of selected models of naked and hydroxylated carbon nanotubes to predict adsorption equilibrium constants for about 30 small aromatic compounds with a variety of functional groups. The equilibrium constants determined using molecular dynamics coupled with free-energy calculation techniques are directly compared to those derived from experimental measurements. The calculations are highly predictive of the relative adsorption affinities of the compounds, with excellent correlation (r ≥ 0.9) between calculated and measured values of the logarithm of the adsorption equilibrium constant. Moreover, the agreement in absolute terms is also reasonable, with average errors of less than one decade. We also explore possible effects of surface loading, although we demonstrate that they are negligible for the experimental conditions considered. Given the degree of reliability demonstrated, we move on to employing the in silico techniques in the design of nanomaterials, using the optimization of adsorption affinity for the herbacide atrazine as an example. Our simulations suggest that, compared to other modifications of graphenic carbon, polyvinylpyrrolidone conjugation gives the highest affinity for atrazine-substantially greater than that of graphenic carbon alone-and may be useful as a nanomaterial for delivery or sequestration of atrazine.

Perturbation of physiological systems by nanoparticles

Nanotechnology is having a tremendous impact on our society. However, societal concerns about human safety under nanoparticle exposure may derail the broad application of this promising technology. Nanoparticles may enter the human body via various routes, including respiratory pathways, the digestive tract, skin contact, intravenous injection, and implantation. After absorption, nanoparticles are carried to distal organs by the bloodstream and the lymphatic system. During this process, they interact with biological molecules and perturb physiological systems. Although some ingested or absorbed nanoparticles are eliminated, others remain in the body for a long time. The human body is composed of multiple systems that work together to maintain physiological homeostasis. The unexpected invasion of these systems by nanoparticles disturbs normal cell signaling, impairs cell and organ functions, and may even cause pathological disorders. This review examines the comprehensive health risks of exposure to nanoparticles by discussing how nanoparticles perturb various physiological systems as revealed by animal studies. The potential toxicity of nanoparticles to each physiological system and the implications of disrupting the balance among systems are emphasized.

Biocompatibility of engineered nanoparticles for drug delivery

The rapid advancement of nanotechnology has raised the possibility of using engineered nanoparticles that interact within biological environments for treatment of diseases. Nanoparticles interacting with cells and the extracellular environment can trigger a sequence of biological effects. These effects largely depend on the dynamic physicochemical characteristics of nanoparticles, which determine the biocompatibility and efficacy of the intended outcomes. Understanding the mechanisms behind these different outcomes will allow prediction of the relationship between nanostructures and their interactions with the biological milieu. At present, almost no standard biocompatibility evaluation criteria have been established, in particular for nanoparticles used in drug delivery systems. Therefore, an appropriate safety guideline of nanoparticles on human health with assessable endpoints is needed. In this review, we discuss the data existing in the literature regarding biocompatibility of nanoparticles for drug delivery applications. We also review the various types of nanoparticles used in drug delivery systems while addressing new challenges and research directions. Presenting the aforementioned information will aid in getting one step closer to formulating compatibility criteria for biological systems under exposure to different nanoparticles.

Trivalent PEGylated platform for the conjugation of bioactive compounds

PEGylated multivalent structures are a new class of platform for biological applications due to their biocompatibility properties. Here, we present the synthesis of a trivalent structure 1 based on poly(ethylene glycol) units (PEG) as potential synthetic multifunctional carrier molecule. To evaluate whether this PEGylated platform could be useful for the conjugation of bioactive compounds, a well-known lipopolysaccharide (LPS) inhibitor 2, developed in our laboratory, was selected to be conjugated to 1. The LPS-neutralizing activity of the resulted conjugates and precursors was established using the chromogenic Limulus amebocyte lysate (LAL) assay. The trivalent structure 1 did not show LPS-binding activity, nonconjugate LPS inhibitor 2 showed high LPS-neutralizing activity, and the trivalent conjugate 4 displayed increased LPS-neutralizing activity and a reduced toxicity profile. These results prove the efficacy of this trivalent platform as a multivalent ligand scaffold for biological applications.

Nucleic acid-binding polymers as anti-inflammatory agents

Dead and dying cells release nucleic acids. These extracellular RNAs and DNAs can be taken up by inflammatory cells and activate multiple nucleic acid-sensing toll-like receptors (TLR3, 7, 8, and 9). The inappropriate activation of these TLRs can engender a variety of inflammatory and autoimmune diseases. The redundancy of the TLR family encouraged us to seek materials that can neutralize the proinflammatory effects of any nucleic acid regardless of its sequence, structure or chemistry. Herein we demonstrate that certain nucleic acid-binding polymers can inhibit activation of all nucleic acid-sensing TLRs irrespective of whether they recognize ssRNA, dsRNA or hypomethylated DNA. Furthermore, systemic administration of such polymers can prevent fatal liver injury engendered by proinflammatory nucleic acids in an acute toxic shock model in mice. Therefore these polymers represent a novel class of anti-inflammatory agent that can act as molecular scavengers to neutralize the proinflammatory effects of various nucleic acids.

Do nanomedicines require novel safety assessments to ensure their safety for long-term human use?

Nanomaterials have different chemical, physical and biological characteristics than larger materials of the same chemical composition. These differences give nanotechnology a double identity: their use implies novel and interesting medical and/or industrial applications but also potential danger for human and environmental health. Here, we briefly review the most important types of nanomaterials, the difficulties in assessing safety or toxicity, and describe existing test protocols used in nanomaterial safety evaluation. In general, the big challenge of nanotechnology, particularly for nanomedicine (nano-bioengineering), is to understand which nano-specific characteristics interact with particular biological systems and functions in order to optimize the therapeutic potential and reduce the undesired responses. The evaluation of the safety of medicinal nanomaterials, especially for long-term application, is an important challenge for the near future. At present, it is still too early to predict, on the basis of the characteristics of the nanomaterial, a possible biological response because no reliable database exists. Therefore, a case-by-case approach for hazard identification is still required, so it is difficult to establish a risk assessment framework.

Immunological properties of engineered nanomaterials

Most research on the toxicology of nanomaterials has focused on the effects of nanoparticles that enter the body accidentally. There has been much less research on the toxicology of nanoparticles that are used for biomedical applications, such as drug delivery or imaging, in which the nanoparticles are deliberately placed in the body. Moreover, there are no harmonized standards for assessing the toxicity of nanoparticles to the immune system (immunotoxicity). Here we review recent research on immunotoxicity, along with data on a range of nanotechnology-based drugs that are at different stages in the approval process. Research shows that nanoparticles can stimulate and/or suppress the immune responses, and that their compatibility with the immune system is largely determined by their surface chemistry. Modifying these factors can significantly reduce the immunotoxicity of nanoparticles and make them useful platforms for drug delivery.

Synthesis and screening of a small library of proline-based biodendrimers for use as delivery agents

A small library of defined peptide dendrimers based on polyproline sequences was designed to demonstrate the feasibility of generating a new type of polymeric agent for therapeutic use. Structural modifications to dendrimer surfaces further enriched the diversity of the library. Data show that the prolinerich dendrimers can be internalized in human epithelial (HeLa) cells, demonstrating the importance of the dendrimeric motif. The promising results described herein suggest that controlled modification of the dendrimer surface should eventually yield proline dendrimers with therapeutic potential.