Tunable length of cyclic peptide–polymer conjugate self-assemblies in water

Polymers conjugated to cyclic peptides capable of forming strong hydrogen bonds can self-assemble into supramolecular bottlebrushes even in aqueous solutions. However, controlling the aggregation of these supramolecular assemblies remains an obstacle that is yet to be overcome. By introducing pH-responsive poly(dimethylamino ethyl methacrylate) (pDMAEMA) arms, the repulsive forces were tuned by adjusting the degree of protonation on the polymer arms. Neutron scattering experiments demonstrated that conjugates in an uncharged state will self-assemble into supramolecular bottlebrushes. Reducing the pH in the system led to a decrease in the number of aggregation, which was reversible by addition of base. Potentiometric titration showed a correlation between the number of aggregation and the degree of ionization of the pDMAEMA arms. Hence, a balance between the strength of the hydrogen bonds and the repulsive electrostatic interactions determines the number of aggregation and extent of self-assembly. The presented work demonstrates that conjugate self-association can be controlled by tuning the charge density on the conjugated polymer arms, paving the way for the use of responsive cyclic peptide conjugates in pharmaceutical applications

Cyclic peptide-poly(HPMA) nanotubes as drug delivery vectors : in vitro assessment, pharmacokinetics and biodistribution

Size and shape have progressively appeared as some of the key factors influencing the properties of nanosized drug delivery systems. In particular, elongated materials are thought to interact differently with cells and therefore may allow alterations of in vivo fate without changes in chemical composition. A challenge, however, remains the creation of stable self-assembled materials with anisotropic shape for delivery applications that still feature the ability to disassemble, avoiding organ accumulation and facilitating clearance from the system. In this context, we report on cyclic peptide-polymer conjugates that self-assemble into supramolecular nanotubes, as confirmed by SANS and SLS. Their behaviour ex and in vivo was studied: the nanostructures are non-toxic up to a concentration of 0.5 g L and cell uptake studies revealed that the pathway of entry was energy-dependent. Pharmacokinetic studies following intravenous injection of the peptide-polymer conjugates and a control polymer to rats showed that the larger size of the nanotubes formed by the conjugates reduced renal clearance and elongated systemic circulation. Importantly, the ability to slowly disassemble into small units allowed effective clearance of the conjugates and reduced organ accumulation, making these materials interesting candidates in the search for effective drug carriers

Systematic study of the structural parameters affecting the self-assembly of cyclic peptide–poly(ethylene glycol) conjugates

Self-assembling cyclic peptides (CP) consisting of amino acids with alternating D- and L-chirality form nanotubes by hydrogen bonding, hydrophobic interactions, and π–π stacking in solution. These highly dynamic materials are emerging as promising supramolecular systems for a wide range of biomedical applications. Herein, we discuss how varying the polymer conformation (linear vs. brush), as well as the number of polymer arms per peptide unimer affects the self-assembly of PEGylated cyclic peptides in different solvents, using small angle neutron scattering. Using the derived information, strong correlations were drawn between the size of the aggregates, solvent polarity, and its ability to compete for hydrogen bonding interactions between the peptide unimers. Using these data, it could be possible to engineer cyclic peptide nanotubes of a controlled length

Supramolecular cyclic peptide-polymer nanotubes as drug delivery vectors

The objective of this thesis is to develop a range of polymeric nanotubes based on self-assembling cyclic peptides suitable to be used as drug delivery systems, and to investigate their behaviour in vitro and in vivo. The interest for cylindrical structures in a drug delivery context arises from their reported longer circulation times, and enhanced tumour accumulation in vivo compared to spherical nanoparticles. Moreover, supramolecular systems have attracted a lot of attention thanks to their versatility and potential ability to facilitate clearance. The design of polymeric nanotubes constructed around a cyclic peptide scaffold is described, and various systems are developed. Firstly, the two main synthetic routes (grafting-to and grafting-from) yielding peptide-polymer conjugates are compared in a systematic study, which shows that the two approaches present distinct advantages, and are complementary in nature. This information is then used to design cyclic peptide conjugates specifically directed to drug delivery, using a polymer that combines biocompatible properties and functional handles. Analysis of their self-assembly in solution confirms the cylindrical shape of the obtained supramolecular structures, and a study of their behaviour in vitro and in vivo establishes their potential as delivery systems. Subsequently, the complexation of a highly potent organometallic anticancer agent is described. In vitro studies determined that the use of the nanotubes leads to higher potency and enhanced selectivity towards cancer cells. Finally, a core-shell system designed for drug encapsulation and subsequent pH-triggered release is presented. This approach relies on the use of an amphiphilic and pH responsive system, which in addition confers more stability to the obtained nanotubes. The work presented in this thesis provides a bottom-up approach in the design of novel self-assembled cyclic peptide nanotubes highly tuned for drug delivery applications

Photo-polymerization induced polymersome rupture

Poly(butadiene)-b-poly(ethylene oxide) (PBut2.5-b-PEO1.3) giant polymersomes were prepared using an emulsion-centrifugation method. The impact of a fast decrease of the osmotic pressure inside the lumen of giant PBut-b-PEO vesicles was studied by confocal microscopy. This osmotic imbalance was created by performing the photo-induced polymerization of acrylamide inside these giant polymersomes, mimicking cell-like confinement. Experimental conditions (irradiation time, relative concentration of monomer and photo-initiator) were optimized to induce the fastest and highest osmotic pressure difference in bulk solution. When confined inside polymersomes with low permeability membrane made of PBut-b-PEO copolymers, this hyper-osmotic shock induced a fast disruption of the membrane and polymersome burst. These findings, complementary to hypo-osmotic shock approaches previously reported, are demonstrating the versatility and relevance of controlling and modulating osmotic pressure imbalance in self-assembled artificial cell systems and protocells

pH-Responsive, Amphiphilic Core–Shell Supramolecular Polymer Brushes from Cyclic Peptide–Polymer Conjugates

The synthesis and self-assembly of pH-responsive, amphiphilic cyclic peptide–polymer conjugates are described. The design relies on the introduction of a poly­(2-(diisopropylamino)­ethyl methacrylate) (pDPA) block between the cyclic peptide and a hydrophilic block. These conjugates are disassembled and protonated at low pH but assemble into core–shell nanotubes at physiological pH, as determined by a combination of titration experiments and scattering techniques

Cyclic peptide–polymer nanotubes as efficient and highly potent drug delivery systems for organometallic anticancer complexes

Background and Purpose Risk of cardiac conduction slowing (QRS/PR prolongations) is assessed prior to clinical trials using in vitro and in vivo studies. Understanding the quantitative translation of these studies to the clinical situation enables improved risk assessment in the nonclinical phase. Experimental Approach Four compounds that prolong QRS and/or PR (AZD1305, flecainide, quinidine and verapamil) were characterized using in vitro (sodium/calcium channels), in vivo (guinea pigs/dogs) and clinical data. Concentration-matched translational relationships were developed based on in vitro and in vivo modelling, and the in vitro to clinical translation of AZD1305 was quantified using an in vitro model. Key Results Meaningful (10%) human QRS/PR effects correlated with low levels of in vitro Nav1.5 block (3–7%) and Cav1.2 binding (13–21%) for all compounds. The in vitro model developed using AZD1305 successfully predicted QRS/PR effects for the remaining drugs. Meaningful QRS/PR changes in humans correlated with small effects in guinea pigs and dogs (QRS 2.3–4.6% and PR 2.3–10%), suggesting that worst-case human effects can be predicted by assuming four times greater effects at the same concentration from dog/guinea pig data. Conclusion and Implications Small changes in vitro and in vivo consistently translated to meaningful PR/QRS changes in humans across compounds. Assuming broad applicability of these approaches to assess cardiovascular safety risk for non–arrhythmic drugs, this study provides a means of predicting human QRS/PR effects of new drugs from effects observed in nonclinical studies

Glycosylated Reversible Addition–Fragmentation Chain Transfer Polymers with Varying Polyethylene Glycol Linkers Produce Different Short Interfering RNA Uptake, Gene Silencing, and Toxicity Profiles

Achieving efficient and targeted delivery of short interfering (siRNA) is an important research challenge to overcome to render highly promising siRNA therapies clinically successful. Challenges exist in designing synthetic carriers for these RNAi constructs that provide protection against serum degradation, extended blood retention times, effective cellular uptake through a variety of uptake mechanisms, endosomal escape, and efficient cargo release. These challenges have resulted in a significant body of research and led to many important findings about the chemical composition and structural layout of the delivery vector for optimal gene silencing. The challenge of targeted delivery vectors remains, and strategies to take advantage of nature’s self-selective cellular uptake mechanisms for specific organ cells, such as the liver, have enabled researchers to step closer to achieving this goal. In this work, we report the design, synthesis, and biological evaluation of a novel polymeric delivery vector incorporating galactose moieties to target hepatic cells through clathrin-mediated endocytosis at asialoglycoprotein receptors. An investigation into the density of carbohydrate functionality and its distance from the polymer backbone is conducted using reversible addition–fragmentation chain transfer polymerization and postpolymerization modification