an-injectable-drug-loaded-supramolecular-hydrogel-for-local-catheter

An Injectable and Drug-loaded Supramolecular Hydrogel for Local Catheter Injection into the Pig Heart

Regeneration of lost myocardium is an important goal for future therapies because of the increasing occurrence of chronic ischemic heart failure and the ...

Expression systems based on self-cleavable intein domains allow the generation of recombinant proteins with a C-terminal thioester. This uniquely reactive C-terminus can be used in native chemical ligation reactions to introduce synthetic groups or to immobilize proteins on surfaces and nanoparticles. Unfortunately, common refolding procedures for recombinant proteins that contain disulfide bonds do not preserve the thioester functionality and therefore novel refolding procedures need to be developed.

One-step refolding and purification of disulfide-containing proteins with a C-terminal MESNA thioester.

Phage display is widely used for the selection of target-specific peptide sequences. Presentation of phage peptides on a multivalent platform can be used to (partially) restore the binding affinity. Here, we present a detailed analysis of the effects of valency, linker choice, and receptor density on binding affinity of a multivalent architecture, using streptavidin (SA) as model multivalent receptor. For surfaces with low receptor densities, the SA binding affinity of multivalent dendritic phage peptide constructs increases over 2 orders of magnitude over the monovalent species (e.g., K(d,mono) = 120 μM vs K(d,tetra) = 1 μM), consistent with previous work. However, the affinity of the SA-binding phage presenting the exact same peptides was 16 pM when dense receptor surfaces used for initial phage display were used in assays. The phage affinity for SA-coated surfaces weakens severely toward the nanomolar regime when surface density of SA is decreased. A similarly strong dependence in this respect was observed for dendritic phage analogues. When presented with a dense SA-coated surface, dendrimer display affords up to a 10(4)-fold gain in affinity over the monovalent peptide. The interplay between ligand valency and receptor density is a fundamental aspect of multivalent targeting strategies in biological systems. The perspective offered here suggests that in vivo targeting schemes might best be served to conduct ligand selection under physiologically relevant receptor density surfaces, either by controlling the receptor density placed at the selection surface or by using more biologically relevant intact cells and tissues.

From phage display to dendrimer display: insights into multivalent binding.

A convenient method to prepare supramolecular bioconjugates in a facile and scalable manner is by a modular approach, whereby self-assembling units and peptides are coupled using oxime chemistry. We here report syntheses of bioactive ureidopyrimidinone-based peptide conjugates, and their resultant self-assembly into fibrous structures.

Modular synthesis of supramolecular ureidopyrimidinone-peptide conjugates using an oxime ligation strategy.

A modular one-component supramolecular transient network in water, based on poly(ethylene glycol) and end-capped with four-fold hydrogen bonding units, is reported. Due to its nonlinear structural formation, this system allows active proteins to be added to the hydrogel during formation. Once implanted in vivo it releases the protein by erosion of both the protein and polymer via dissolution.

Hierarchical formation of supramolecular transient networks in water: a modular injectable delivery system.

Minimally invasive intervention strategies after myocardial infarction use state-of-the-art catheter systems that are able to combine mapping of the infarcted area with precise, local injection of drugs. To this end, catheter delivery of drugs that are not immediately pumped out of the heart is still challenging, and requires a carrier matrix that in the solution state can be injected through a long catheter, and instantaneously gelates at the site of injection. To address this unmet need, a pH-switchable supramolecular hydrogel is developed. The supramolecular hydrogel is switched into a liquid at pH > 8.5, with a viscosity low enough to enable passage through a 1-m long catheter while rapidly forming a hydrogel in contact with tissue. The hydrogel has self-healing properties taking care of adjustment to the injection site. Growth factors are delivered from the hydrogel thereby clearly showing a reduction of infarct scar in a pig myocardial infarction model.

A fast pH-switchable and self-healing supramolecular hydrogel carrier for guided, local catheter injection in the infarcted myocardium.

In natural systems, highly synergistic non-covalent interactions among biomolecular components exert mesoscopic control over hierarchical assemblies. We herein present a multicomponent self-assembly strategy to tune hierarchical supramolecular polymer architectures in water using highly affine and directional ureidopyrimidinone-poly(ethylene glycol)s (UPy-PEG). Using scattering methods and oscillatory rheology, we observe the structural and mechanical regulation of entangled monofunctional UPy-PEG fibrils by cross-linking bifunctional UPy-PEG fibrils. This supramolecular mixing approach opens the door to a range of subtly distinct materials for chemical and biological applications.

Mesoscale modulation of supramolecular ureidopyrimidinone-based poly(ethylene glycol) transient networks in water.

Activation of endogenous cardiac stem/progenitor cells (eCSCs) can improve cardiac repair after acute myocardial infarction. We studied whether the in situ activation of eCSCs by insulin-like growth factor 1 (IGF-1) and hepatocyte growth factor (HGF) could be increased using a newly developed hydrogel in chronic myocardial infarction (MI). One-month post-MI pigs underwent NOGA-guided intramyocardial injections of IGF-1/HGF (GF: both 0.5 μg/mL, n = 5) or IGF-1/HGF incorporated in UPy hydrogel (UPy-GF; both 0.5 μg/mL, n = 5). UPy hydrogel without added growth factors was administered to four control (CTRL) pigs. Left ventricular ejection fraction was increased in the UPy-GF and GF animals compared to CTRLs. UPy-GF delivery reduced pathological hypertrophy, led to the formation of new, small cardiomyocytes, and increased capillarization. The eCSC population was increased almost fourfold in the border zone of the UPy-GF-treated hearts compared to CTRL hearts. These results show that IGF-1/HGF therapy led to an improved cardiac function in chronic MI and that effect size could be further increased by using UPy hydrogel.

Sustained delivery of insulin-like growth factor-1/hepatocyte growth factor stimulates endogenous cardiac repair in the chronic infarcted pig heart.

Hydrogels and, in particular, supramolecular hydrogels show promising properties for application in regenerative medicine because of their ability to adapt to the natural environment these materials are brought into. However, only few studies focus on the structure-property relationships in supramolecular hydrogels. Here, we study in detail both the structure and the mechanical properties of such a network, composed of poly(ethylene glycol), end-functionalized with ureido-pyrimidinone fourfold hydrogen bonding units. This network is responsive to triggers such as concentration, temperature and pH. To obtain more insight into the sol-gel transition of the system, both rheology and small-angle X-ray scattering (SAXS) are used. We show that the sol-gel transitions based on these three triggers, as measured by rheology, coincide with the appearance of a structural feature in SAXS. We attribute this feature to the presence of hydrophobic domains where cross-links are formed. These results provide more insight into the mechanism of network formation in these materials, which can be exploited for tailoring their behavior for biomedical applications, where one of the triggers discussed might be used.

Article	Year
One-step refolding and purification of disulfide-containing proteins with a C-terminal MESNA thioester. BMC biotechnology\| PubMed ID: 18828922	2008
From phage display to dendrimer display: insights into multivalent binding. Journal of the American Chemical Society\| PubMed ID: 21473586	2011
Modular synthesis of supramolecular ureidopyrimidinone-peptide conjugates using an oxime ligation strategy. Chemical communications (Cambridge, England)\| PubMed ID: 22010132	2012
Hierarchical formation of supramolecular transient networks in water: a modular injectable delivery system. Advanced materials (Deerfield Beach, Fla.)\| PubMed ID: 22528786	2012
A fast pH-switchable and self-healing supramolecular hydrogel carrier for guided, local catheter injection in the infarcted myocardium. Advanced healthcare materials\| PubMed ID: 23788397	2014
Mesoscale modulation of supramolecular ureidopyrimidinone-based poly(ethylene glycol) transient networks in water. Journal of the American Chemical Society\| PubMed ID: 23829684	2013
Sustained delivery of insulin-like growth factor-1/hepatocyte growth factor stimulates endogenous cardiac repair in the chronic infarcted pig heart. Journal of cardiovascular translational research\| PubMed ID: 24395494	2014
Mesoscale characterization of supramolecular transient networks using SAXS and rheology. International journal of molecular sciences\| PubMed ID: 24441567	2014

Maartje M. C. Bastings

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