Poly-L-Lysine-Poly[HPMA] Block Copolymers Obtained by RAFT Polymerization as Polyplex-Transfection Reagents with Minimal Toxicity

PLL-Poly(HPMA) Bottlebrush-Based Antifouling Coatings: Three Grafting Routes

In this work, we compare three routes to prepare antifouling coatings that consist of poly(l-lysine)-poly(N-(2-hydroxypropyl)methacrylamide) bottlebrushes. The poly(l-lysine) (PLL) backbone is self-assembled onto the surface by charged-based interactions between the lysine groups and the negatively charged silicon oxide surface, whereas the poly(N-(2-hydroxypropyl)methacrylamide) [poly(HPMA)] side chains, grown by reversible addition-fragmentation chain-transfer (RAFT) polymerization, provide antifouling properties to the surface. First, the PLL-poly(HPMA) coatings are synthesized in a bottom-up fashion through a grafting-from approach. In this route, the PLL is self-assembled onto a surface, after which a polymerization agent is immobilized, and finally HPMA is polymerized from the surface. In the second explored route, the PLL is modified in solution by a RAFT agent to create a macroinitiator. After self-assembly of this macroinitiator onto the surface, poly(HPMA) is polymerized from the surface by RAFT. In the third and last route, the whole PLL-poly(HPMA) bottlebrush is initially synthesized in solution. To this end, HPMA is polymerized from the macroinitiator in solution and the PLL-poly(HPMA) bottlebrush is then self-assembled onto the surface in just one step (grafting-to approach). Additionally, in this third route, we also design and synthesize a bottlebrush polymer with a PLL backbone and poly(HPMA) side chains, with the latter containing 5% carboxybetaine (CB) monomers that eventually allow for additional (bio)functionalization in solution or after surface immobilization. These three routes are evaluated in terms of ease of synthesis, scalability, ease of characterization, and a preliminary investigation of their antifouling performance. All three coating procedures result in coatings that show antifouling properties in single-protein antifouling tests. This method thus presents a new, simple, versatile, and highly scalable approach for the manufacturing of PLL-based bottlebrush coatings that can be synthesized partly or completely on the surface or in solution, depending on the desired production process and/or application.

Ring opening polymerization of α-amino acids: advances in synthesis, architecture and applications of polypeptides and their hybrids

This review provides a comprehensive overview of the latest advances in the synthesis, architectural design and biomedical applications of polypeptides and their hybrids.

Impact of Cationic Charge Density and PEGylated Poly(amino acid) Tercopolymer Architecture on Their Use as Gene Delivery Vehicles. Part 1: Synthesis, Self-Assembly, and DNA Complexation

The interaction of PEGylated poly(amino acid)s with their biological targets depends on their chemical nature and spatial arrangement of their building blocks. The synthesis, self-assembly, and DNA complexation of ABC terblock copolymers consisting of poly(ethylene glycol), (PEG), poly(l-lysine), and poly(l-leucine), are reported. Block copolymers are produced by a metal-free, living ring-opening polymerization of respective amino acid N-carboxyanhydrides using amino-terminated PEG as macroinitiator: (PEG-b-p(l-Lys)_x -b-p(l-Leu)_y , PEG-b-p(l-Leu)_x -b-p(l-Lys)_y , and PEG-b-p((l-Lys)_x -co-p(l-Leu)_y ). Sizes of self-assembled nanoparticles depend on the formation method. The nanoprecipitation method proves useful for copolymers with the poly(l-lysine) block protected as trifluoroacetate, effective diameters range between 92 and 132 nm, while direct dissolution in distilled water is suitable for the deprotected copolymers, yielding effective diameters between 52 and 173 nm. Critical micelle concentration (CMC) analyses corroborate particle size analyses and show a distinct impact of the molecular architecture; the lowest CMC (8 µg mL^-1 ) is observed when the poly(l-leucine) segment forms the C-block and the hydrophilic, disassembly driving poly(l-lysine) segment is short. DNA complexation, evaluated by gel motility and RiboGreen analyses, depends strongly on the molecular architecture. A more efficient DNA complexation is observed when poly(l-lysine) and poly(l-leucine) form individual blocks as opposed to them forming a copolymer.

Site-Specific DBCO Modification of DEC205 Antibody for Polymer Conjugation

The design of multifunctional polymer-based vectors, forming pDNA vaccines, offers great potential in cancer immune therapy. The transfection of dendritic immune cells (DCs) with tumour antigen-encoding pDNA leads to an activation of the immune system to combat tumour cells. In this work, we investigated the chemical attachment of DEC205 antibodies (aDEC205) as DC-targeting structures to polyplexes of P(Lys)-b-P(HPMA). The conjugation of a synthetic block copolymer and a biomacromolecule with various functionalities (aDEC205) requires bioorthogonal techniques to avoid side reactions. Click chemistry and in particular the strain-promoted alkyne-azide cycloaddition (SPAAC) can provide the required bioorthogonality. With regard to a SPAAC of both components, we firstly synthesized two different azide-containing block copolymers, P(Lys)-b-P(HPMA)-N₃(stat) and P(Lys)-b-P(HPMA)-N₃(end), for pDNA complexation. In addition, the site-specific incorporation of ring-strained dibenzocyclooctyne (DBCO) moieties to the DEC205 antibody was achieved by an enzymatic strategy using bacterial transglutaminase (BTG). The chemical accessibility of DBCO molecules within aDEC205 as well as the accessibility of azide-functionalities on the polyplex' surface were investigated by various SPAAC experiments and characterized by fluorescence correlation spectroscopy (FCS).

Design of Poly-l-Glutamate-Based Complexes for pDNA Delivery

Due to the polyanionic nature of DNA, typically cationic or neutral delivery vehicles have been used for gene delivery. As a new approach, this study focuses on the design, development, and validation of nonviral polypeptide-based carriers for oligonucleotide delivery based on a negatively charged poly-l-glutamic acid (PGA) backbone partly derivatized with oligoaminoamide residues. To this end, PGA-derivatives modified with different pentameric succinyl tetraethylene pentamines (Stp₅ ) are designed. Optionally, histidines for modulation of endosomal buffer capacity and cysteines for pDNA complex stabilization are included, followed by characterization of biophysical properties and gene transfer efficiency in N2a neuroblastoma or 4T1 breast cancer cells.

Covalent nano delivery systems for selective imaging and treatment of brain tumors

Nanomedicine is a rapidly evolving form of therapy that holds a great promise for superior drug delivery efficiency and therapeutic efficacy than conventional cancer treatment. In this review, we attempt to cover the benefits and the limitations of current nanomedicines with special attention to covalent nano conjugates for imaging and drug delivery in the brain. The improvement in brain tumor treatment remains dismal despite decades of efforts in drug development and patient care. One of the major obstacles in brain cancer treatment is the poor drug delivery efficiency owing to the unique blood-brain barrier (BBB) in the CNS. Although various anti-cancer agents are available to treat tumors outside of the CNS, the majority fails to cross the BBB. In this regard, nanomedicines have increasingly drawn attention due to their multi-functionality and versatility. Nano drugs can penetrate BBB and other biological barriers, and selectively accumulate in tumor cells, while concurrently decreasing systemic toxicity.

Intracellular responsive dual delivery by endosomolytic polyplexes carrying DNA anchored porous silicon nanoparticles

Bioresponsive cytosolic nanobased multidelivery has been emerging as an enormously challenging novel concept due to the intrinsic protective barriers of the cells and hardly controllable performances of nanomaterials. Here, we present a new paradigm to advance nano-in-nano integration technology amenable to create multifunctional nanovehicles showing considerable promise to overcome restrictions of intracellular delivery, solve impediments of endosomal localization and aid effectual tracking of nanoparticles. A redox responsive intercalator chemistry comprised of cystine and 9-aminoacridine is designed as a cross-linker to cap carboxylated porous silicon nanoparticles with DNA. These intelligent nanocarriers are then encapsulated within novel one-pot electrostatically complexed nano-networks made of a zwitterionic amino acid (cysteine), an anionic bioadhesive polymer (poly(methyl vinyl ether-alt-maleic acid)) and a cationic endosomolytic polymer (polyethyleneimine). This combined nanocomposite is successfully tested for the co-delivery of hydrophobic (sorafenib) or hydrophilic (calcein) molecules loaded within the porous core, and an imaging agent covalently integrated into the polyplex shell by click chemistry. High loading capacity, low cyto- and hemo-toxicity, glutathione responsive on-command drug release, and superior cytosolic delivery are shown as achievable key features of the proposed formulation. Overall, formulating drug molecules, DNA and imaging agents, without any interference, in a physico-chemically optimized carrier may open a path towards broad applicability of these cost-effective multivalent nanocomposites for treating different diseases.