Polyethylenimine as a Versatile Simultaneous Reducing and Stabilizing Agent Enabling One-Pot Synthesis of Transition-Metal Nanoparticles: Fundamental Aspects and Practical Implications.

The large surface area of metallic nanoparticles provides them with particular optical, chemical, and biological properties, accordingly enabling their use in a wide array of applications. In this regard, facile and fast synthetic approaches are desirable for ready-to-use functional materials. Following early investigations focused on the direct synthesis of polymer-coated gold nanoparticles, we herein demonstrate that such a strategy can be used to manufacture different types of d-block transition-metal nanoparticles via a one-pot method in aqueous media and mild temperature conditions. Gold (Au3+), palladium (Pd2+), and silver (Ag+) ions could be reduced using only polyethylenimine (PEI) or PEI derivatives acting simultaneously as a reducing and stabilizing agent and without the aid of any other external agent. The process gave rise, for instance, to Pd urchin-like nanostructures with a large surface area which confers to them outstanding catalytic performance compared to AuNPs and AgNPs produced using the same strategy. The polymer-stabilized AgNPs were demonstrated to be biocide against a variety of microorganisms, although AuNPs and PdNPs do not hold such an attribute at least in the probed concentration range. These findings may provide significant advances toward the practical, facile, and ready-to-use manufacturing of transition-metal nanoparticles for a myriad of applications.

Role of Membrane Features on the Permeability Behavior of Polymersomes and the Potential Impacts on Drug Encapsulation and Release.

Self-assembled bilayer structures such as those produced from amphiphilic block copolymers (polymersomes) are potentially useful in a wide array of applications including the production of artificial cells and organelles, nanoreactors, and delivery systems. These constructs are of important fundamental interest, and they are also frequently considered toward advances in bionanotechnology and nanomedicine. In this framework, membrane permeability is perhaps the most important property of such functional materials. Having in mind these considerations, we herein report the manufacturing of intrinsically permeable polymersomes produced using block copolymers comprising poly[2-(diisopropylamino)-ethyl methacrylate] (PDPA) as the hydrophobic segment. Although being water insoluble at pH 7.4, its pKa(PDPA) ∼ 6.8 leads to the presence of a fraction of protonated amino groups close to the physiological pH, thus conducting the formation of relatively swollen hydrophobic segments. Rhodamine B-loaded vesicles demonstrated that this feature confers inherent permeability to the polymeric membrane, which can still be modulated to some extent by the solution pH. Indeed, even at higher pH values where the PDPA chains are fully deprotonated, the experiments demonstrate that the membranes remain permeable. While membrane permeability can be, for instance, regulated by introducing membrane proteins and DNA nanopores, examples of membrane-forming polymers with intrinsic permeability have been seldom reported so far, and the possibility to regulate the flow of chemicals in these compartments by tuning block copolymer features and ambient conditions is of due relevance. The permeable nature of PDPA membranes possibly applies to a wide array of small molecules, and these findings can in principle be translocated to a variety of disparate bio-related applications.

The Protein Corona Conundrum: Exploring the Advantages and Drawbacks of its Presence around Amphiphilic Nanoparticles.

The success of targeted drug delivery systems still requires a detailed understanding about the biological consequences of self-developed biomolecular coronas around them, since this is the surface that interacts with living cells. Herein, we report the behavior of carbohydrate-decorated amphiphilic nanoparticles in a plasma environment with regard to the formation and biological consequences of the protein corona. Naked amphiphilic nanoparticles were produced through the self-assembly of azido-PEO900-docosanoate molecules, and the coupling of N-acetylglucosamine via click chemistry enabled the fabrication of the corresponding bioactive glyco-nanostructures. Light scattering measurements, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, liquid chromatography-mass spectrometry, and the Pierce BCA protein assay all confirmed the presence of protein coronas around the self-assembled nanoparticles, regardless of the presence of the sugar residues, although it reduces the amount of adsorbed proteins. The protein coronas were formed mainly by human serum albumin, complement proteins, apolipoproteins, immunoglobulins, and proteins involved in the coagulation cascade (fibrinogen and prothrombin). While the presence of these protein coronas significantly reduced cellular uptake of the amphiphilic assemblies, they also notably reduced the cytotoxic and hemolytic effects that result from the contact of the nanoparticles with living cells. Accordingly, we highlight that protein coronas should not always be treated as artifacts that have to be avoided because they can also provide beneficial effects.

Polyglycidol-Stabilized Nanoparticles as a Promising Alternative to Nanoparticle PEGylation: Polymer Synthesis and Protein Fouling Considerations.

We herein demonstrate the outstanding protein-repelling characteristic of star-like micelles and polymersomes manufactured from amphiphilic block copolymers made by poly(butylene oxide) (PBO) hydrophobic segments and polyglycidol (PGL) hydrophilic outer shells. Although positively charged proteins (herein modeled by lysozyme) may adsorb onto the surface of micelles and polymersomes where the assemblies are stabilized by short PGL chains (degree of polymerization smaller than 15), the protein adsorption vanishes when the degree of polymerization of the hydrophilic segment (PGL) is higher than ∼20, regardless the morphology. This has been probed by using three different model proteins which are remarkably different concerning molecular weight, size, and zeta potential (bovine serum albumin (BSA), lysozyme, and immunoglobulin G (IgG)). Indeed, the adsorption of the most abundant plasma protein (herein modeled as BSA) is circumvented even by using very short PGL shells due to the highly negative zeta potential of the produced assemblies which presumably promote protein-nanoparticle electrostatic repulsion. The negative zeta potential, on the other hand, enables lysozyme adsorption, and the phenomenon is governed by electrostatic forces as evidenced by isothermal titration calorimetry. Nevertheless, the protein coating can be circumvented by slightly increasing the degree of polymerization of the hydrophilic segment. Notably, the PGL length required to circumvent protein fouling is significantly smaller than the one required for PEO. This feature and the safety concerns regarding the synthetic procedures on the preparation of poly(ethylene oxide)-based amphiphilic copolymers might make polyglycidol a promising alternative toward the production of nonfouling spherical particles.

Reactive Oxygen Species (ROS)-Responsive Polymersomes with Site-Specific Chemotherapeutic Delivery into Tumors via Spacer Design Chemistry.

The lack of cellular and tissue specificities in conventional chemotherapies along with the generation of a complex tumor microenvironment (TME) limits the dosage of active agents that reaches tumor sites, thereby resulting in ineffective responses and side effects. Therefore, the development of selective TME-responsive nanomedicines is of due relevance toward successful chemotherapies, albeit challenging. In this framework, we have synthesized novel, ready-to-use ROS-responsive amphiphilic block copolymers (BCs) with two different spacer chemistry designs to connect a hydrophobic boronic ester-based ROS sensor to the polymer backbone. Hydrodynamic flow focusing nanoprecipitation microfluidics (MF) was used in the preparation of well-defined ROS-responsive PSs; these were further characterized by a combination of techniques [1H NMR, dynamic light scattering (DLS), static light scattering (SLS), transmission electron microscopy (TEM), and cryogenic TEM (cryo-TEM)]. The reaction with hydrogen peroxide releases an amphiphilic phenol or a hydrophilic carboxylic acid, which affects polymersome (PS) stability and cargo release. Therefore, the importance of the spacer chemistry in BC deprotection and PS stability and cargo release is herein highlighted. We have also evaluated the impact of spacer chemistry on the PS-specific release of the chemotherapeutic drug doxorubicin (DOX) into tumors in vitro and in vivo. We demonstrate that by spacer chemistry design one can enhance the efficacy of DOX treatments (decrease in tumor growth and prolonged animal survival) in mice bearing EL4 T cell lymphoma. Side effects (weight loss and cardiotoxicity) were also reduced compared to free DOX administration, highlighting the potential of the well-defined ROS-responsive PSs as TME-selective nanomedicines. The PSs could also find applications in other environments with high ROS levels, such as chronic inflammations, aging, diabetes, cardiovascular diseases, and obesity.

Sweetness Reduces Cytotoxicity and Enables Faster Cellular Uptake of Sub-30 nm Amphiphilic Nanoparticles.

Glycoconjugates are versatile entities used for the manufacturing of targeted drug delivery nanocontainers because of their outstanding capability to bind to lectins, which are proteins that can be found overexpressed in the membranes of unhealthy cells. The assisted attachment to pathological cells can further enable a more efficient intracellular delivery of loaded active agents, thereby reducing side effects that commonly compromise chemotherapies. In this framework, azide-terminated polyethylene oxide (PEO) chains coupled to a 22-carbon chain were synthesized (azide-PEO900-docosanoate). The resulting amphiphile was further functionalized by introducing different sugar moieties to the PEO chains via the click chemistry approach. Sub-30 nm, negatively charged, and spherical nanoparticles were prepared in water by self-assembly of the synthesized molecules using the straightforward nanoprecipitation protocol. The produced entities do not induce hemolysis in red blood cells at c ≤ 200 µg mL-1, and they are not cytotoxic to healthy cells [telomerase immortalized rhesus fibroblasts (Telo-RF)] at c ≤ 50 µg mL-1. The sugar-decorated nanoparticles are less cytotoxic compared with their naked counterparts at the concentration range assessed. The kinetics of cellular uptake of both entities into normal (Telo-RF) and tumor (HeLa) cells were monitored via fluorescence microscopy and flow cytometry. The nanoparticles are internalized faster in cancer cells than in normal cells, regardless of functionalization. Moreover, the functionalized nanoparticles are internalized faster in HeLa cells, while the reverse was observed in healthy Telo-RF cells. The distinct surface characteristics of the assemblies create an opportunity to expedite the uptake of nanoparticles particularly by tumor cells, and this accordingly can lead to a more effective intracellular delivery of therapeutic molecules loaded into nanoparticle's reservoirs.

Microfluidic-Assisted Engineering of Quasi-Monodisperse pH-Responsive Polymersomes toward Advanced Platforms for the Intracellular Delivery of Hydrophilic Therapeutics.

The extracellular and subcellular compartments are characterized by specific pH levels that can be modified by pathophysiological states. This scenario encourages the use of environmentally responsive nanomedicines for the treatment of damaged cells. We have engineered doxorubicin (DOX)-loaded pH-responsive polymersomes using poly([ N-(2-hydroxypropyl)]methacrylamide)- b-poly[2-(diisopropylamino)ethyl methacrylate] block copolymers (PHPMA m- b-PDPA n). We demonstrate that, by taking advantage of the microfluidic technology, quasi-monodisperse assemblies can be created. This feature is of due relevance because highly uniform nanoparticles commonly exhibit more consistent biodistribution and cellular uptake. We also report that the size of the polymer vesicles can be tuned by playing with the inherent mechanical parameters of the microfluidic protocol. This new knowledge can be used to engineer size-specific nanomedicines for enhanced tumor accumulation if the manufacturing is performed with previous knowledge of tumor characteristics (particularly the degree of vascularity and porosity). The pH-dependent DOX release was further investigated evidencing the ability of polymersome to sustain encapsulated hydrophilic molecules when circulating in physiological environment (pH 7.4). This suggests nonrelevant drug leakage during systemic circulation. On the other hand, polymersome disassembly in slightly acid environments takes place enabling fast DOX release, thereby making the colloidal carriers highly cytotoxic. These features encourage the use of such advanced pH-responsive platforms to target damaged cells while preserving healthy environments during systemic circulation.

Nanoparticle-Cell Interactions: Surface Chemistry Effects on the Cellular Uptake of Biocompatible Block Copolymer Assemblies.

The development of nanovehicles for intracellular drug delivery is strongly bound to the understating and control of nanoparticles cellular uptake process, which in turn is governed by surface chemistry. In this study, we explored the synthesis, characterization, and cellular uptake of block copolymer assemblies consisting of a pH-responsive poly[2-(diisopropylamino)ethyl methacrylate] (PDPA) core stabilized by three different biocompatible hydrophilic shells (a zwitterionic type poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) layer, a highly hydrated poly(ethylene oxide) (PEO) layer with stealth effect, and an also proven nontoxic and nonimmunogenic poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA) layer). All particles had a spherical core-shell structure. The largest particles with the thickest hydrophilic stabilizing shell obtained from PMPC40-b-PDPA70 were internalized to a higher level than those smaller in size and stabilized by PEO or PHPMA and produced from PEO122-b-PDPA43 or PHPMA64-b-PDPA72, respectively. Such a behavior was confirmed among different cell lines, with assemblies being internalized to a higher degree in cancer (HeLa) as compared to healthy (Telo-RF) cells. This fact was mainly attributed to the stronger binding of PMPC to cell membranes. Therefore, cellular uptake of nanoparticles at the sub-100 nm size range may be chiefly governed by the chemical nature of the stabilizing layer rather than particles size and/or shell thickness.

Gene Transfection Mediated by Catiomers Requires Free Highly Charged Polymer Chains To Overcome Intracellular Barriers.

The prospective use of the block copolymers poly(ethylene oxide)113-b-poly[2-(diethylamino)ethyl methacrylate]50 (PEO113-b-PDEA50) and poly[oligo(ethylene glycol)methyl ether methacrylate]70-b-poly[oligo(ethylene glycol)methyl ether methacrylate10-co-2-(diethylamino)ethyl methacrylate47-co-2-(diisopropylamino)ethyl methacrylate47] (POEGMA70-b-P(OEGMA10-co-DEA47-co-DPA47)) as nonviral gene vectors was evaluated. The polymers are able to properly condense DNA into nanosized particles (RH ≈ 75 nm), which are marginally cytotoxic and can be uptaken by cells. However, the green fluorescent protein (GFP) expression assays evidenced that DNA delivery is essentially negligible meaning that intracellular trafficking hampers efficient gene release. Subsequently, we demonstrate that cellular uptake and particularly the quantity of GFP-positive cells are substantially enhanced when the block copolymer polyplexes are produced and further supplemented by BPEI chains (branched polyethylenimine). The dynamic light scattering/electrophoretic light scattering/isothermal titration calorimetry data suggest that such a strategy allows the adsorption of BPEI onto the surface of the polyplexes, and this phenomenon is responsible for increasing the size and surface charge of the assemblies. Nevertheless, most of the BPEI chains remain freely diffusing in the systems. The biological assays confirmed that cellular uptake is enhanced in the presence of BPEI and principally, the free highly charged polymer chains play the central role in intracellular trafficking and gene transfection. These investigations pointed out that the transfection efficiency versus cytotoxicity issue can be balanced by a mixture of BPEI and less cytotoxic agents such as for instance the proposed block copolymers.

Efficient Condensation of DNA into Environmentally Responsive Polyplexes Produced from Block Catiomers Carrying Amine or Diamine Groups.

The intracellular delivery of nucleic acids requires a vector system as they cannot diffuse across lipid membranes. Although polymeric transfecting agents have been extensively investigated, none of the proposed gene delivery vehicles fulfill all of the requirements needed for an effective therapy, namely, the ability to bind and compact DNA into polyplexes, stability in the serum environment, endosome-disrupting capacity, efficient intracellular DNA release, and low toxicity. The challenges are mainly attributed to conflicting properties such as stability vs efficient DNA release and toxicity vs efficient endosome-disrupting capacity. Accordingly, investigations aimed at safe and efficient therapies are still essential to achieving gene therapy clinical success. Taking into account the mentioned issues, herein we have evaluated the DNA condensation ability of poly(ethylene oxide)113-b-poly[2-(diisopropylamino)ethyl methacrylate]50 (PEO113-b-PDPA50), poly(ethylene oxide)113-b-poly[2-(diethylamino)ethyl methacrylate]50 (PEO113-b-PDEA50), poly[oligo(ethylene glycol)methyl ether methacrylate]70-b-poly[oligo(ethylene glycol)methyl ether methacrylate10-co-2-(diethylamino)ethyl methacrylate47-co-2-(diisopropylamino)ethyl methacrylate47] (POEGMA70-b-P(OEGMA10-co-DEA47-co-DPA47), and poly[oligo(ethylene glycol)methyl ether methacrylate]70-b-poly{oligo(ethylene glycol)methyl ether methacrylate10-co-2-methylacrylic acid 2-[(2-(dimethylamino)ethyl)methylamino]ethyl ester44} (POEGMA70-b-P(OEGMA10-co-DAMA44). Block copolymers PEO113-b-PDEA50 and POEGMA70-b-P(OEGMA10-co-DEA47-co-DPA47) were evidenced to properly condense DNA into particles with a desirable size for cellular uptake via endocytic pathways (R(H) ≈ 65-85 nm). The structure of the polyplexes was characterized in detail by scattering techniques and atomic force microscopy. The isothermal titration calorimetric data revealed that the polymer/DNA binding is endothermic; therefore, the process in entropically driven. The combination of results supports that POEGMA70-b-P(OEGMA10-co-DEA47-co-DPA47) condenses DNA more efficiently and with higher thermodynamic outputs than does PEO113-b-PDEA50. Finally, circular dichroism spectroscopy indicated that the conformation of DNA remained the same after complexation and that the polyplexes are very stable in the serum environment.

Understanding the structural parameters of biocompatible nanoparticles dictating protein fouling.

The development of nanocarriers for biomedical applications requires that these nanocarriers have special properties, including resistance to nonspecific protein adsorption. In this study, the fouling properties of PLA- and PCL-based block copolymer nanoparticles (NPs) have been evaluated by placing them in contact with model proteins. Block copolymer NPs were produced through the self-assembly of PEOm-b-PLAn and PEOm-b-PCLn. This procedure yielded nanosized objects with distinct structural features dependent on the length of the hydrophobic and hydrophilic blocks and the volume ratio. The protein adsorption events were examined in relation to size, chain length, surface curvature, and hydrophilic chain density. Fouling by BSA and lysozyme was considerably reduced as the length of the hydrophilic PEO-stabilizing shell increases. In contrast to the case of hydrophilic polymer-grafted planar surfaces, the current investigations suggest that the hydrophilic chain density did not markedly influence protein fouling. The protein adsorption took place at the outer surface of the NPs since neither BSA nor lysozyme was able to diffuse within the hydrophilic layer due to geometric restrictions. Protein binding is an exothermic process, and it is modulated mainly by polymer features. The secondary structures of BSA and lysozyme were not affected by the adhesion phenomena.

Evaluation of polymersome permeability as a fundamental aspect towards the development of artificial cells and nanofactories.

Polymersomes are synthetic vesicles with potential use in healthcare, chemical transformations in confined environment (nanofactories), and in the construction of artificial cells and organelles. In this framework, one of the most important features of such supramolecular structures is the permeability behavior allowing for selective control of mass exchange between the inner and outer compartments. The use of biological and synthetic nanopores in this regard is the most common strategy to impart permeability nevertheless, this typically requires fairly complex strategies to enable porosity. Yet, investigations concerning the permeability of polymer vesicles to different analytes still requires further exploration and, taking these considerations into account, we have detailed investigated the permeability behavior of a variety of polymersomes with regard to different analytes (water, protons, and rhodamine B) which were selected as models for solvents, ions, and small molecules. Polymersomes based on hydrophilic blocks of poly[N-(2-hydroxypropyl)methacrylamide] (PHPMA) or PEO (poly(ethylene oxide)) linked to the non-responsive blocks poly[N-(4-isopropylphenylacetamide)ethyl methacrylate] (PPPhA) or poly(methyl methacrylate) (PMMA), or to the stimuli pH-responsive block poly[2-(diisopropylamino)ethyl methacrylate] (PDPA) have been investigated. Interestingly, the produced PEO-based vesicles are notably larger than the ones produced using PHPMA-containing block copolymers. The experimental results reveal that all the vesicles are inherently permeable to some extent with permeability behavior following exponential profiles. Nevertheless, polymersomes based on PMMA as the hydrophobic component were demonstrated to be the least permeable to the small molecule rhodamine B as well as to water. The synthetic vesicles based on the pH-responsive PDPA block exhibited restrictive and notably slow proton permeability as attributed to partial chain protonation upon acidification of the medium. The dye permeability was evidenced to be much slower than ion or solvent diffusion, and in the case of pH-responsive assemblies, it was demonstrated to also depend on the ionic strength of the environment. These findings are understood to be highly relevant towards polymer selection for the production of synthetic vesicles with selective and time-dependent permeability, and it may thus contribute in advancing biomimicry and nanomedicine.

Balancing gene transfection and cytotoxicity of nucleic acid carriers with focus on ocular and hepatic disorders: evaluation of hydrophobic and hydrophilic polyethyleneimine derivatives.

Polyethyleneimine (PEI) derivatives substituted by lactose, succinic acid or alkyl domains were evaluated as nonviral gene delivery vectors towards balancing gene transfection and cytotoxicity. The investigations were focused on pDNA transfection into arising retinal pigment epithelia (ARPE-19) and human hepatocellular carcinoma (HepG2) cell lines. The first mentioned cell line was chosen as motivated by the non-negligible number of ocular disorders linked to gene aberrations, whereas the second one is a cell line overexpressing the asialoglycoprotein receptor (ASGP-R), which can bind to galactose residues. The presence of short alkyl domains (C4 and C6), and particularly the succinylation of the PEI chains, improved the biological outputs of the gene vectors. The presence of hydrophobic units possibly enhances lytic activity, whereas the incorporation of succinic acid slightly reduces polymer-DNA interaction strength, thereby enabling more efficient intracellular unpacking and cargo release. Succinylation is also supposed to decrease cytotoxicity and avoid protein adsorption to the polyplexes. The presence of long carbon chains (for instance, C12) nevertheless, results in higher levels of cytotoxicity and respective lower transfection rates. The sugar-decorated polyplexes are overall less cytotoxic, but the presence of lactose moieties also leads to larger polyplexes and notably weak polymer-DNA binding, which compromise the transfection efficiency. Yet, along with the presence of short lytic alkyl domains, the double-substitution of PEI synergistically boosts gene transfection probably due to the uptake of higher DNA and polymer amounts without cell damage. Overall, the experimental data suggest that ocular and hepatic gene therapies may be potentialized by fine-tuning the hydrophobic-to-hydrophilic balance, and succinic acid is a favorable motif for the modification of PEI.

Tuning the morphology of block copolymer-based pH-triggered nanoplatforms as driven by changes in molecular weight and protocol of manufacturing.

The ability to tune size and morphology of self-assemblies is particularly relevant in the development of delivery systems. By tailoring such structural parameters, one can provide larger cargo spaces or produce nanocarriers that can be loaded by hydrophilic and hydrophobic molecules starting ideally from the same polymer building unit. We herein demonstrate that the morphology of block copolymer-based pH-triggered nanoplatforms produced from poly(2-methyl-2-oxazoline)m-b-poly[2-(diisopropylamino)-ethyl methacrylate]n (PMeOxm-b-PDPAn) is remarkably influenced by the overall molecular weight of the block copolymer, and by the selected method used to produce the self-assemblies. Polymeric vesicles were produced by nanoprecipitation using a block copolymer of relatively low molecular weight (Mn âˆ¼ 10 kg.mol-1). Very exciting though, despite the high hydrophobic weight ratio (wPDPA > 0.70), this method conducted to the formation of core-shell nanoparticles when block copolymers of higher molecular weight were used, thus suggesting that the fast (few seconds) self-assembly procedure is controlled by kinetics rather than thermodynamics. We further demonstrated the formation of vesicular structures using longer chains via the solvent-switch approach when the "switching" to the bad solvent is performed in a time scale of a few hours (approximately 3 hs). We accordingly demonstrate that using fairly simple methods one can easily tailor the morphology of such block copolymer self-assemblies, thereby producing a variety of structurally different pH-triggered nanoplatforms via a kinetic or thermodynamically-controlled process. This is certainly attractive towards the development of nanotechnology-based cargo delivery systems.

Self-assembly of amphiphilic glycoconjugates into lectin-adhesive nanoparticles.

This work describes the synthesis and self-assembly of carbohydrate-clicked rod-coil amphiphilic systems. Copper-catalyzed Huisgen cycloaddition was efficiently employed to functionalize the hydrophilic extremity of PEG-b-tetra(p-phenylene) conjugates by lactose and N-acetyl-glucosamine ligands. The resulting amphiphilic systems spontaneously self-assembled into nanoparticles when dissolved in aqueous media, as evidenced by dynamic light scattering (DLS), transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS). The formation of highly monodisperse micelles having a mean diameter of 10 nm was observed for systems containing a PEG 900 core, and a decrease in the hydrophilic moiety (PEG 600) led to the formation of vesicles with a broader size distribution. The presence of carbohydrate residues on the surfaces of the micelles and their ability to establish specific interactions with wheat germ agglutinin (WGA) and peanut agglutinin (PNA) were further highlighted by light-scattering measurements, thus confirming the attractive applications of such sugar micelles in biosensor devices.

Protein coronas coating polymer-stabilized silver nanocolloids attenuate cytotoxicity with minor effects on antimicrobial performance.

Silver nanoparticles are versatile platforms with a variety of applications in the biomedical field. In this framework, their presence in biological media inevitably leads to the interaction with proteins thus conducting to the formation of biomolecular coronas. This feature alters the identity of the nanomaterial and may affect many biological events. These considerations motivated the investigation of protein adsorption onto the surface of polymer-stabilized AgNPs. The metallic colloids were coated by polyethyleneimine (PEI), polyvinylpyrrolidone (PVP), and poly(2-vinyl pyridine)-b-poly(ethylene oxide) (PEO-b-P2VP), and nanoparticle-protein interaction was probed by using a library of analytical techniques. The experimental data revealed a higher extent of protein adsorption at the surface of AgNPs@PVP whereas PEO-b-P2VP coating conducted to the least amount. The main component of the protein coronas was evidenced to be bovine serum albumin (BSA), which is indeed the protein at the highest abundancy in the model biological media. We have further demonstrated reduced cytotoxicity of the silver colloids coated by biomolecular coronas as compared to the pristine counterparts. Nevertheless, the protein coatings did not notably reduce the antimicrobial performance of the polymer-stabilized AgNPs. Accordingly, although the protein-repelling property is frequently targeted towards longer in vivo circulation of nanoparticles, we herein underline that protein coatings, which are commonly treated as artifacts to be avoided, may indeed enhance the biological performance of nanomaterials. These findings are expected to be highly relevant in the design of polymer-stabilized metallic colloids intended to be used in healthcare.

Reduced cytotoxicity of nanomaterials driven by nano-bio interactions: Case study of single protein coronas enveloping polymersomes.

The protein adsorption onto poly(acrylic acid)-block-polystyrene (PAA22-b-PS144) polymersomes has been investigated with regard to structural features, thermodynamic aspects and biological consequences. The light scattering measurements revealed the formation of protein coronas enveloping the polymeric capsules regardless of the chemical nature of the biomacromolecules. The experiments were conducted by using lysozyme, immunoglobulin G - IgG and bovine serum albumin - BSA as model proteins due to their differences concerning size and residual surface charge at physiological pH. The protein adsorption was further confirmed by isothermal titration calorimetry, and the experimental data suggest that the phenomenon is mainly governed by hydrogen bonding and van der Waals interactions. The pre-existing protein layer via the pre-incubation in protein environments notably attenuates the cytotoxicity of the nanomaterial compared to the pristine counterparts. This approach can possibly be extended to different types of assemblies when intermolecular interactions are able to induce protein adsorption and the development of protein coronas around nanoparticles. Such fairly simple method may be convenient to engineer safer nanomaterials towards a variety of biomedical applications when the nanotoxicity is an issue. Additionally, the strategy can possibly be used to tailor the surface properties of nanoparticles by adsorbing specific proteins for targeting purposes.

Ready-to-use room temperature one-pot synthesis of surface-decorated gold nanoparticles with targeting attributes.

Gold nanoparticles (AuNPs) can be used in diagnostic and therapeutic applications. The development of facile and fast synthetic approaches is accordingly desirable towards ready-to-use biomedical materials. We report a practical one-pot method for the synthesis in aqueous media and room temperature of surface-decorated AuNPs with enhanced biological responses. The gold ions could be reduced using only polyethyleneimine (PEI) derivatives containing sugar and-or alkyl chains acting simultaneously as reducing and stabilizing agent, without the aid of any other mediator. The process is possibly potentialized by the presence of the amino groups in the polymer chains which further confer colloidal stability. The kinetics of AuNPs nucleation and growth depends on the chemical nature of the polymer chains. Particularly, the presence of lactose moieties conjugated to the PEI chains conducted to surface-decorated AuNPs with low cytotoxicity that are remarkably faster uptaken by HepG2 cells. These cells overexpress asialoglycoprotein (ASGP-R), a galactose receptor. These findings may kick off significant advances towards the practical and ready-to-use manufacturing of functionalized AuNPs towards cell-targeting since the methodology is applicable for a large variety of other ligands that can be conjugated to the same polymer chains.

Current Designs of Polymeric Platforms Towards the Delivery of Nucleic Acids Inside the Cells with Focus on Polyethylenimine.

BACKGROUND: Gene delivery is a promising technology for treating diseases linked to abnormal gene expression. Since nucleic acids are the therapeutic entities in such approach, a transfecting vector is required because the macromolecules are not able to efficiently enter the cells by themselves. Viral vectors have been evidenced to be highly effective in this context; however, they suffer from fundamental drawbacks, such as the ability to stimulate immune responses. The development of synthetic vectors has accordingly emerged as an alternative. OBJECTIVES: Gene delivery by using non-viral vectors is a multi-step process that poses many challenges, either regarding the extracellular or intracellular media. We explore the delivery pathway and afterwards, we review the main classes of non-viral gene delivery vectors. We further focus on the progresses concerning polyethylenimine-based polymer-nucleic acid polyplexes, which have emerged as one of the most efficient systems for delivering genetic material inside the cells. DISCUSSION: The complexity of the whole transfection pathway, along with a lack of fundamental understanding, particularly regarding the intracellular trafficking of nucleic acids complexed to non-viral vectors, probably justifies the current (beginning of 2021) limited number of formulations that have progressed to clinical trials. Truly, successful medical developments still require a lot of basic research. CONCLUSION: Advances in macromolecular chemistry and high-resolution imaging techniques will be useful to understand fundamental aspects towards further optimizations and future applications. More investigations concerning the dynamics, thermodynamics and structural parameters of polyplexes would be valuable since they can be connected to the different levels of transfection efficiency hitherto evidenced.

Evidence of protein coronas around soft nanoparticles regardless of the chemical nature of the outer surface: structural features and biological consequences.

The formation of biomolecular coronas around nanoparticles as soon as they come in contact with biological media is nowadays well accepted. The self-developed biological outer surfaces can affect the targeting capability of the colloidal carriers as well as their cytotoxicity and cellular uptake behavior. In this framework, we explored the structural features and biological consequences of protein coronas around block copolymer assemblies consisting of a common pH-responsive core made by poly[2-(diisopropylamino) ethyl methacrylate] (PDPA) and hydrophilic shells of different chemical natures: zwitterionic poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) or highly hydrophilic poly(ethylene oxide) (PEO) and poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA). We demonstrated the presence of ∼50 nm protein coronas around the nanoparticles regardless of the chemical nature of the polymeric shells. The thickness is understood as the sum of the soft and hard layers and it is the actual interface seen by the cells. Although the soft corona composition is difficult to determine because the proteins are loosely bound to the outer surface of the assemblies, the tightly bound proteins (hard corona) could be identified and quantified. The compositional analysis of the hard corona demonstrated that human serum albumin (HSA), immunoglobulin G (IgG) and fibrinogen are the main components of the protein coronas, and serotransferrin is present particularly in the protein corona of the zwitterionic-stabilized assemblies. The protein coronas substantially reduce the cellular uptake of the colloidal particles due to their increased size and the presence of HSA which is known to reduce nanoparticle-cell adhesion. On the other hand, their existence also reduces the levels of cytotoxicity of the polymeric assemblies, highlighting that protein coronas should not be always understood as artifacts that need to be eliminated due to their positive outputs.