Unusual Salt and pH Induced Changes in Polyethylenimine Solutions

Electrolyte-Electrocatalyst Interfacial Effects of Polymeric Materials for Tandem CO2 Capture and Conversion Elucidated Using In Situ Electrochemical AFM

Integrating CO2 capture and electrochemical conversion has been proposed as a strategy to reduce the net energy required for CO2 regeneration in traditional CO2 capture and conversion schemes and can be coupled with carbon-free renewable electricity. Polyethylenimine (PEI)-based materials have been previously studied as CO2 capture materials and can be integrated in these reactive capture processes. PEI-based electrolytes have been found to significantly increase the CO2 loading, and impact selectivity and rate of product formation when compared to the conventional aqueous electrolytes. However, the influence of these materials at the catalyst-electrode interface is currently not well understood. In this study, PEI-based electrolytes were prepared and their impact on the morphology of a silver electrode performing electrochemical CO2 reduction (CO2R) was studied using in situ electrochemical atomic force microscopy (EC-AFM). The presence of PEI on the electrode surface could be distinguished based on nanomechanical properties (DMT modulus), and changes were observed as negative polarization was applied, revealing a reorganization of the PEI chains due to electrostatic interactions. These changes were impacted by the electrolyte composition, including the addition of supporting electrolyte KHCO3 salt, as well as CO2 captured by the PEI-based electrolyte, which minimized the change in surface mechanical properties and degree of PEI alignment on the electrode surface. The changes in surface mechanical properties were also dependent on the PEI polymer length, with higher molecular weight PEI showing different reconfiguration than the shorter polymer brushes. The study highlights that the choice of polymer material, the electrolyte composition, and CO2 captured impact the near-electrode environment, which has implications for CO2R, and presents EC-AFM as a new tool that can be used to probe the dynamic behavior of these interfaces during electrocatalysis.

Mechanoresponsive Protein Crystals for NADH Recycling in Multicycle Enzyme Reactions

NAD(H)-dependent enzymes play a crucial role in the biosynthesis of pharmaceuticals and fine chemicals, but the limited recyclability of the NAD(H) cofactor hinders its more general application. Here, we report the generation of mechano-responsive PEI-modified Cry3Aa protein crystals and their use for NADH recycling over multiple reaction cycles. For demonstration of its practical utility, a complementary Cry3Aa protein particle containing genetically encoded and co-immobilized formate dehydrogenase for NADH regeneration and leucine dehydrogenase for catalyzing the NADH-dependent l-tert-leucine (l-tert-Leu) biosynthesis has been produced. When combined with the PEI-modified Cry3Aa crystal, the resultant reaction system could be used for the efficient biosynthesis of l-tert-Leu for up to 21 days with a 10.5-fold improvement in the NADH turnover number.

Recent Progress in the Endosomal Escape Mechanism and Chemical Structures of Polycations for Nucleic Acid Delivery

Nucleic acid-based therapies are seeing a spiralling surge. Stimuli-responsive polymers, especially pH-responsive ones, are gaining widespread attention because of their ability to efficiently deliver nucleic acids. These polymers can be synthesized and modified according to target requirements, such as delivery sites and the nature of nucleic acids. In this regard, the endosomal escape mechanism of polymer-nucleic acid complexes (polyplexes) remains a topic of considerable interest owing to various plausible escape mechanisms. This review describes current progress in the endosomal escape mechanism of polyplexes and state-of-the-art chemical designs for pH-responsive polymers. The importance is also discussed of the acid dissociation constant (i.e., pKa) in designing the new generation of pH-responsive polymers, along with assays to monitor and quantify the endosomal escape behavior. Further, the use of machine learning is addressed in pKa prediction and polymer design to find novel chemical structures for pH responsiveness. This review will facilitate the design of new pH-responsive polymers for advanced and efficient nucleic acid delivery.

Linear Polyethyleneimine-Based and Metal Organic Frameworks (DUT-67) Composite Hydrogels as Efficient Sorbents for the Removal of Methyl Orange, Copper Ions, and Penicillin V

This research explores the integration of DUT-67 metal organic frameworks into polyethyleneimine-based hydrogels to assemble a composite system with enough mechanical strength, pore structure and chemical affinity to work as a sorbent for water remediation. By varying the solvent-to-modulator ratio in a water-based synthesis path, the particle size of DUT-67 was successfully modulated from 1 μm to 200 nm. Once DUT-67 particles were integrated into the polymeric hydrogel, the composite hydrogel exhibited enhanced mechanical properties after the incorporation of the MOF filler. XPS, NMR, TGA, FTIR, and FT Raman studies confirmed the presence and interaction of the DUT-67 particles with the polymeric chains within the hydrogel network. Adsorption studies of methyl orange, copper(II) ions, and penicillin V on the composite hydrogel revealed a rapid adsorption kinetics and monolayer adsorption according to the Langmuir's model. The composite hydrogel demonstrated higher adsorption capacities, as compared to the pristine hydrogel, showcasing a synergistic effect, with maximum adsorption capacities of 473 ± 21 mg L-1, 86 ± 6 mg L-1, and 127 ± 4 mg L-1, for methyl orange, copper(II) ions, and penicillin V, respectively. This study highlights the potential of MOF-based composite hydrogels as efficient adsorbents for environmental pollutants and pharmaceuticals.

Synthesis of vancomycin functionalized fluorescent gold nanoparticles and selective sensing of mercury (II)

Mercury ions (Hg2+) are widely found in the environment; it is considered a major pollutant. Therefore, the rapid and reliable detection of Hg2+ is of great technical interest. In this study, a highly fluorescent, sensitive, and selective fluorometric assay for detecting Hg2+ ions was developed using vancomycin functionalized and polyethyleneimine stabilized gold nanoparticles (PEI-f-AuNPs@Van). The as-made gold nanoparticles were highly fluorescent, with excitation and emission maxima occurring at 320 and 418 nm, respectively. The size of nanoparticles was ~7 nm; a zeta potential of ~38.8 mV was determined. The XRD analysis confirmed that the nanoparticles possessed crystalline structure with face centerd cubic symmetry. Using the PEI-f-AuNP@Van probe, the detection limit of Hg2+ ion was achieved up to 0.988 nM (within a linear range) by calculating the KSV. However, the detection limit in a natural environmental sample was shown to be 12.5 nM. Furthermore, the selectivity tests confirmed that the designed probe was highly selective to mercury (II) cations among tested other divalent cations. Owing to its sensitivity and selectivity, this approach for Hg2+ ions detection can be utilized for the analysis of real water samples.

Delivery of Chemotherapy Agents and Nucleic Acids with pH-Dependent Nanoparticles

With less than one percent of systemically injected nanoparticles accumulating in tumors, several novel approaches have been spurred to direct and release the therapy in or near tumors. One such approach depends on the acidic pH of the extracellular matrix and endosomes of the tumor. With an average pH of 6.8, the extracellular tumor matrix provides a gradient for pH-responsive particles to accumulate, enabling greater specificity. Upon uptake by tumor cells, nanoparticles are further exposed to lower pHs, reaching a pH of 5 in late endosomes. Based on these two acidic environments in the tumor, various pH-dependent targeting strategies have been employed to release chemotherapy or the combination of chemotherapy and nucleic acids from macromolecules such as the keratin protein or polymeric nanoparticles. We will review these release strategies, including pH-sensitive linkages between the carrier and hydrophobic chemotherapy agent, the protonation and disruption of polymeric nanoparticles, an amalgam of these first two approaches, and the release of polymers shielding drug-loaded nanoparticles. While several pH-sensitive strategies have demonstrated marked antitumor efficacy in preclinical trials, many studies are early in their development with several obstacles that may limit their clinical use.

Determination of the microscopic acid dissociation constant of piperacillin and identification of dissociated molecular forms

For amphoteric ß-lactam antibiotics, the acid dissociation constant (pK a) is a fundamental parameter to characterize physicochemical and biochemical properties of antibiotics and to predict persistence and removal of drugs. pK a of piperacillin (PIP) is determined by potentiometric titration with a glass electrode. Electrospray ionization mass spectrometry (ESI-MS) is creatively applied to verify the reasonable pK a value at every dissociation step. Two microscopic pK a values (3.37 ± 0.06 and 8.96 ± 0.10) are identified and attributed to the direct dissociation of the carboxylic acid functional group and one secondary amide group, respectively. Different from other ß-lactam antibiotics, PIP presents a dissociation pattern where direct dissociation is involved instead of protonation dissociation. Moreover, the degradation tendency of PIP in an alkaline solution may alter the dissociation pattern or dismiss the corresponding pK a of the amphoteric ß-lactam antibiotics. This work offers a reliable determination of the acid dissociation constant of PIP and a clear interpretation of the effect of stability of antibiotics on the dissociation process.

Immune response and protective efficacy of mannosylated polyethylenimine (PEI) as an antigen delivery vector, administered with a Streptococcus agalactiae DNA vaccine in Nile tilapia (Oreochromis niloticus)

This study examined the effectiveness of a DNA vaccine for S. agalactiae that was delivered by mannose-based polyethyleneimine (Man-PEI). The results showed that Man-PEI/pcDNA-Sip stimulated a higher serum antibody titer compared to control or other vaccine groups (p < 0.05). Additionally, it induced higher expression of immune-related genes, and increased activities of superoxide dismutase (SOD), acid phosphatase (ACP) and alkaline phosphatase (AKP). Furthermore, the Man-PEI/pcDNA-Sip group showed an improved relative percent survival (RPS) of 85.71%. These results demonstrate the potential value of Man-PEI as a vaccine delivery vehicle, and suggest that it can be effective in boosting the immune protective rate induced by pcDNA-Sip vaccines.

Preparation of a Mussel-Inspired Supramolecular Polymer Coating Containing Graphene Oxide on Magnesium Alloys with Anti-Corrosion and Self-Healing Properties

Herein, we present a mussel-inspired supramolecular polymer coating to improve the an-ti-corrosion and self-healing properties of an AZ31B magnesium alloy. A self-assembled coating of polyethyleneimine (PEI) and polyacrylic acid (PAA) is a supramolecular aggregate that takes advantage of the weak interaction of non-covalent bonds between molecules. The cerium-based conversion layers overcome the corrosion problem between the coating and the substrate. Catechol mimics mussel proteins to form adherent polymer coatings. Chains of PEI and PAA interact electrostatically at high density, forming a dynamic binding that causes strand entanglement, enabling the rapid self-healing properties of a supramolecular polymer. The addition of graphene oxide (GO) as an anti-corrosive filler gives the supramolecular polymer coating a superior barrier and impermeability properties. The results of EIS revealed that a direct coating of PEI and PAA accelerates the corrosion of magnesium alloys; the impedance modulus of a PEI and PAA coating is only 7.4 × 10³ Ω·cm², and the corrosion current of a 72 h immersion in a 3.5 wt% NaCl solution is 1.401 × 10^-6 Ω·cm². The impedance modulus of the addition of a catechol and graphene oxide supramolecular polymer coating is up to 3.4 × 10⁴ Ω·cm², outperforming the substrate by a factor of two. After soaking in a 3.5 wt% NaCl solution for 72 h, the corrosion current is 0.942 × 10^-6 A/cm², which is superior to other coatings in this work. Furthermore, it was found that 10-micron scratches were completely healed in all coatings within 20 min, in the presence of water. The supramolecular polymer offers a new technique for the prevention of metal corrosion.

Quantitative nuclear magnetic resonance of chloride by an accurate internal standard approach

Chloride is the most common counterion used to improve aqueous solubility and enhance stability of small molecule active pharmaceutical ingredients. While several analytical techniques, such as titration, HPLC with charged aerosol detection, and ion chromatography, are currently utilized to assay the level of chloride, they have notable limitations, and these instruments may not be readily available. Here, we present a generally applicable ³⁵ Cl solution NMR method to assay the level of chloride in pharmaceutical compounds. The method uses KClO₄ as an internal standard for improved accuracy in comparison with external standard methods, and it was found to be robust, linear over three orders of magnitude, precise (<3% RSD), and accurate (<0.5% absolute error).

Periodic Self-Assembly of Poly(ethyleneimine)-poly(4-styrenesulfonate) Complex Coacervate Membranes

Coacervation is a self-assembly strategy based on the complexation of polyelectrolytes, which is utilized in biomedicine and agriculture, as well as automotive and textile industries. In this paper, we developed a new approach to the on-demand periodic formation of polyelectrolyte complexes through a Liesegang-type hierarchical organization. Adjustment of reaction conditions allows us to assemble materials with a tunable spatiotemporal geometry and establish materials' production cycles with a regulated periodicity. The proposed methodology allows the membrane to self-assemble when striving to reach balance and self-heal after exposure to external stimuli, such as potential difference and high pH. Using chronopotentiometry, K⁺ ion permeability behavior of the PEI-PSS coacervate membranes was demonstrated. The periodically self-assembled polyelectrolyte nanomembranes could further be integrated into novel energy storage devices and intelligent biocompatible membranes for bionics, soft nanorobotics, biosensing, and biocomputing.

Light-responsive self-assembled microstructures of branched polyethyleneimine at low pH

Soft materials comprising polyethyleneimine (PEI), which integrate low pH-stimulated higher-order assemblies (fibres and sheets) with light responsiveness, have been shown. Excitation wavelength light-driven interactions enable the formation of bead-necklace-type structures in fibres or volume collapse of sheets. This work can have significant implications for transfection or encapsulation through PEI-based complexes.

Comparison of tyrosine-modified low molecular weight branched and linear polyethylenimines for siRNA delivery

Polyethylenimines (PEIs) have been previously introduced for siRNA delivery. In particular, in the case of higher molecular weight PEIs, this is associated with toxicity, while low molecular weight PEIs are often insufficient for siRNA complexation. The tyrosine-modification of PEIs has been shown to enhance PEI efficacy and biocompatibility. This paper evaluates a set of tyrosine-modified low molecular weight linear or branched polyethylenimines as efficient carriers of siRNA. Complexation efficacies and biophysical complex properties were analyzed by zeta potential, dynamic light scattering and circular dichroism measurements as well as gel electrophoresis. Biological knockdown was studied in 2 D cell culture and 3 D ex vivo tissue slice air-liquid interface culture. The results demonstrate that siRNAs were able to form stable complexes with all tested polymers. Complexation was able to protect siRNA from degradation by RNase and to mediate target gene knockdown, as determined on the mRNA level and in PC3-Luc3/EGFP and HCT116-Luc3/EGFP expressing reporter cells on the protein level, using flow cytometry and confocal microscopy. The direct comparison of the studied polymers revealed differences in biological efficacies. Moreover, the tyrosine-modified PEIs showed high biocompatibility, as determined by LDH release and mitochondria integrity (J-aggregate assay) as well as caspase 3/7 (apoptosis) and H₂O₂ levels (ROS). In 3 D tissue slices, complexes based on LP10Y proved to be most efficient, by combining tissue penetration with efficient gene expression knockdown.

Preparation of Biocidal Nanocomposites in X-ray Irradiated Interpolyelectolyte Complexes of Polyacrylic Acid and Polyethylenimine with Ag-Ions

Due to the presence of cationic units interpolyelectrolyte complexes (IPECs) can be used as a universal basis for preparation of biocidal coatings on different surfaces. Metallopolymer nanocomposites were successfully synthesized in irradiated solutions of polyacrylic acid (PAA) and polyethylenimine (PEI), and dispersions of non-stoichiometric IPECs of PAA–PEI containing silver ions. The data from turbidimetric titration and dynamic light scattering showed that pH 6 is the optimal value for obtaining IPECs. Metal polymer complexes based on IPEC with a PAA/PEI ratio equal to 3/1 and 1/3 were selected for synthesis of nanocomposites due to their aggregative stability. Studies using methods of UV–VIS spectroscopy and TEM have demonstrated that the size and spatial organization of silver nanoparticles depend on the composition of polymer systems. The average sizes of nanoparticles are 5 nm and 20 nm for complexes with a molar ratio of PAA/PEI units equal to 3/1 and 1/3, respectively. The synthesized nanocomposites were applied to the glass surface and exhibited high antibacterial activity against both gram-positive (Staphylococcus aureus) and gram-negative bacteria (Salmonella). It is shown that IPEC-Ag coatings demonstrate significantly more pronounced biocidal activity not only in comparison with macromolecular complexes of PAA–PEI, but also coatings of PEI and PEI based nanocomposites.

pH-Universal Catechol-Amine Chemistry for Versatile Hyaluronic Acid Bioadhesives

Catechol, a major mussel-inspired underwater adhesive moiety, has been used to develop functional adhesive hydrogels for biomedical applications. However, oxidative catechol chemistry for interpolymer crosslinking and adhesion is exclusively effective under alkaline conditions, with limited applications in non-alkaline conditions. To overcome this limitation, pH-universal catechol-amine chemistry to recapitulate naturally occurring biochemical events induced by pH variation in the mussel foot is suggested. Aldehyde moieties are introduced to hyaluronic acid (HA) by partial oxidation, which enables dual-mode catechol tethering to the HA via both stable amide and reactive secondary amine bonds. Because of the presence of additional reactive amine groups, the resultant aldehyde-modified HA conjugated with catechol (AH-CA) is effectively crosslinked in acidic and neutral pH conditions. The AH-CA hydrogel exhibits not only fast gelation via active crosslinking regardless of pH conditions, but also strong adhesion and excellent biocompatibility. The hydrogel enables rapid and robust wound sealing and hemostasis in neutral and alkaline conditions. The hydrogel also mediates effective therapeutic stem cell and drug delivery even in dynamic and harsh environments, such as a motile heart and acidic stomach. Therefore, the AH-CA hydrogel can serve as a versatile biomaterial in a wide range of pH conditions in vivo.

Multifunctional stimuli-responsive hybrid nanogels for cancer therapy: Current status and challenges

With cancer research shifting focus to achieving multifunctionality in cancer treatment strategies, hybrid nanogels are making a rapid rise to the spotlight as novel, multifunctional, stimuli-responsive, and biocompatible cancer therapeutic strategies. They can possess cancer cell-specific cytotoxic effects themselves, carry drugs or enzymes that can produce cytotoxic effects, improve imaging modalities, and target tumor cells over normal cells. Hybrid nanogels bring together a wide range of desirable properties for cancer treatment such as stimuli-responsiveness, efficient loading and protection of molecules such as drugs or enzymes, and effective crossing of cellular barriers among other properties. Despite their promising abilities, hybrid nanogels are still far from being used in the clinic, and their available data remains relatively limited. However, many studies can be done to facilitate this clinical transition. This review is critically summarizing and analyzing the recent information and progress on the use of hybrid nanogels particularly inorganic nanoparticle-based and organic nanoparticle-based hybrid nanogels in the field of oncology and future directions to aid in transferring those results to the clinic. This work concludes that the future of hybrid nanogels is greatly impacted by therapeutic and non-therapeutic factors. Therapeutic factors include the lack of hemocompatibility studies, acute and chronic toxicological studies, and information on agglomeration capability and extent, tumor heterogeneity, interaction with proteins in physiological fluids, endocytosis-exocytosis, and toxicity of the nanogels' breakdown products. Non-therapeutic factors include the lack of clear regulatory guidelines and standardized assays, limitations of animal models, and difficulties associated with good manufacture practices (GMP).

A Study of the Buffer Capacity of Polyelectrolyte Microcapsules Depending on Their Concentration and the Number of Layers of the Polyelectrolyte Shell

Polyelectrolyte microcapsules are used in the development of new forms of targeted delivery systems, self-healing materials, sensors, and smart materials. Nevertheless, their buffer capacity has not been practically studied, although that characteristic makes it possible to estimate the change in the state of protonation of the entire polyelectrolyte system. This is necessary both for creating a buffer barrier system for pH-sensitive compounds (metals, enzymes, polyelectrolytes, drugs) and for the correct interpretation of the results of research and studying of the PMC structure. The buffer capacity of a PMC can be affected by the concentration of microcapsules in solution and the number of shell layers since the listed parameters affect other physicochemical properties of the PMC shell. This includes, for example, the electrical conductivity, permeability (of ions), osmotic pressure, charge density, etc. In this regard, we studied the change in the buffer capacity of polyelectrolyte microcapsules depending on their concentration and the number of shell layers. As a result, it was found that with an increasing concentration of microcapsules, the buffering capacity of the PMC increases, but at the same time, in the pH range from 4 to 5.5, the calculated buffering capacity of 1 billion capsules decreases with increasing their concentration. This effect may be associated with a decrease in the available -NH2 groups of the PMC’s shell. In addition, it was found that the main contribution to the buffer capacity of a PMC is made by the entire shell of the microcapsule and not just its surface. At the same time, the buffer capacity of the capsules has non-linear growth with an increase in the number of PMC shell layers. It is presumably associated either with a decrease in the polyelectrolyte layer with an increase in their number or with a decrease in the permeability of hydrogen protons.

A Study of the Buffer Capacity of Polyelectrolyte Microcapsules Depending on Their Ionic Environment and Incubation Temperature

Polyelectrolyte microcapsules (PMCs) are used in the development of new forms of drugs, coatings and diagnostic systems. Their buffer capacity, depending on the conditions of the medium, has not been practically studied, although it can affect the structure of both the capsule itself and the encapsulated agents. In this connection, we studied the buffer capacity of polyelectrolyte microcapsules of the composition (polystyrene sulfonate/polyallylamine)₃ ((PSS/PAH)₃) depending on the concentration and the type of salt in solution, as well as the microcapsule incubation temperature. It was found that the buffer capacity of microcapsules in the presence of mono- and di-valent salts of the same ionic strength did not differ practically. Increasing the NaCl concentration to 1 M led to an increase of buffer capacity of PMCs at pH ≥ 5, and an increase in NaCl concentration above 1 M did not change buffer capacity. The study of the buffer capacity of pre-heated PMCs showed that buffer capacity decreased with increasing incubation temperature, which was possibly due to the compaction of the PMCs and an increase in the number of compensated PAH sites. The addition of 1 M sodium chloride to heated PMCs presumably reversed the process described above, since an increase in the ionic strength of the solution led to an increase of the buffer capacity of the PMCs. The effects described above confirm the hypothesis put forward that the buffer properties of microcapsules are determined by uncompensated PAH regions in their composition.

Optimization and Antibacterial Response of N-Halamine Coatings Based on Polydopamine

Due to the ability of microorganisms to first adhere to a material surface and then to lead to the formation of a biofilm, it is essential to develop surfaces that have antimicrobial properties. It is well known that N-halamine coatings allow us to prevent or minimize such phenomena. In the present work, various polydopamine (PDA) coatings containing chloramine functions were studied. In fact, three PDA-based films were formed by the simple immersion of a gold substrate in a dopamine solution, either at pH 8 in the presence or not of polyethyleneimine (PEI), or at pH 5 in the presence of periodate as an oxidant. These films were characterized by polarization modulation reflection absorption infrared spectroscopy and X-ray photoelectron spectroscopy analyses, and by scanning electron microscopy observations. The chlorination of these PDA films was performed by their immersion in a sodium hypochlorite aqueous solution, in order to immobilize Cl(+I) into the (co)polymers (PDA or PDA–PEI). Finally, antibacterial assays towards the Gram-negative bacteria Escherichia coli (E. coli) and the Gram-positive bacteria Staphylococcus epidermidis (S. epidermidis) were conducted to compare the bactericidal properties of these three N-halamine coatings. Regardless of the bacteria tested, the PDA coating with the best antibacterial properties is the coating obtained using periodate.

Nanosensing of Acetylcholine Molecules: Influence of the Association Mechanism

A bullet-shaped nanopore surface modified by two polyelectrolyte (PE) layers, an inner polyethyleneimine (PEI) layer and an outer p-sulfonatocalix[4]-arene (SCX4) layer, is applied to sense trace levels of acetylcholine (Ach) molecules. We show that the higher the order of the association reaction of Ach with SCX4, the smaller the difference between the ionic current when Ach is present and that when it is absent, and so is the difference in the space charge density. In addition, the larger the binding constant K of that reaction, the lower the detection limit but narrower the detection range. Choosing pH 7 is most appropriate because if the pH is low, the concentration polarization of H⁺ is significant, and as it gets high, both PE layers become uncharged. At pH 7 and K = 2 × 10⁷ L/mol, the detection limit of the nanopore ranges from 1 to 10 nM, which is orders of magnitude lower than that of the other approaches.

Polyethyleneimine-Based Lipopolyplexes as Carriers in Anticancer Gene Therapies

Recent years have witnessed rapidly growing interest in application of gene therapies for cancer treatment. However, this strategy requires nucleic acid carriers that are both effective and safe. In this context, non-viral vectors have advantages over their viral counterparts. In particular, lipopolyplexes—nanocomplexes consisting of nucleic acids condensed with polyvalent molecules and enclosed in lipid vesicles—currently offer great promise. In this article, we briefly review the major aspects of developing such non-viral vectors based on polyethyleneimine and outline their properties in light of anticancer therapeutic strategies. Finally, examples of current in vivo studies involving such lipopolyplexes and possibilities for their future development are presented.

Modified Gold Nanoparticles to Overcome the Chemoresistance to Gemcitabine in Mutant p53 Cancer Cells

Mutant p53 proteins result from missense mutations in the TP53 gene, the most mutated in human cancer, and have been described to contribute to cancer initiation and progression. Therapeutic strategies for targeting mutant p53 proteins in cancer cells are limited and have proved unsuitable for clinical application due to problems related to drug delivery and toxicity to healthy tissues. Therefore, the discovery of efficient and safe therapeutic strategies that specifically target mutant p53 remains challenging. In this study, we generated gold nanoparticles (AuNPs) chemically modified with low molecular branched polyethylenimine (bPEI) for the efficient delivery of gapmers targeting p53 mutant protein. The AuNPs formulation consists of a combination of polymeric mixed layer of polyethylene glycol (PEG) and PEI, and layer-by-layer assembly of bPEI through a sensitive linker. These nanoparticles can bind oligonucleotides through electrostatic interactions and release them in the presence of a reducing agent as glutathione. The nanostructures generated here provide a non-toxic and powerful system for the delivery of gapmers in cancer cells, which significantly downregulated mutant p53 proteins and altered molecular markers related to cell growth and apoptosis, thus overcoming chemoresistance to gemcitabine.

Tuning Net Charge in Aliphatic Polycarbonates Alters Solubility and Protein Complexation Behavior

A synthetic strategy yielded polyelectrolytes and polyampholytes with tunable net charge for complexation and protein binding. Organocatalytic ring-opening polymerizations yielded aliphatic polycarbonates that were functionalized with both carboxylate and ammonium side chains in a post-polymerization, radical-mediated thiol-ene reaction. Incorporating net charge into the polymer architecture altered the chain dimensions in phosphate buffered solution in a manner consistent with self-complexation and complexation behavior with model proteins. A net cationic polyampholyte with 5% of carboxylate side chains formed large clusters rather than small complexes with bovine serum albumin, while 50% carboxylate polyampholyte was insoluble. Overall, the aliphatic polycarbonates with varying net charge exhibited different macrophase solution behaviors when mixed with protein, where self-complexation appears to compete with protein binding and larger-scale complexation.

The effect of PEGylation on the efficacy and uptake of an immunostimulatory nanoparticle in the tumor immune microenvironment

The efficacy of immunotherapies is often limited by the immunosuppressive tumor microenvironment, which is populated with dysfunctional innate immune cells. To reprogram the tumor-resident innate immune cells, we developed immunostimulatory silica mesoporous nanoparticles (immuno-MSN). The cargo of immuno-MSN is a Stimulator of Interferon Gene (STING) agonist, which activates innate immune cells leading to production of interferon (IFN) β. By proficiently trafficking its cargo into immune cells, the immuno-MSN induced a 9-fold increase of IFN-β secretion compared to free agonist. While an external PEG shield has historically been used to protect nanoparticles from immune recognition, a PEGylated immunostimulatory nanoparticle needs to strike a balance between immune evasion to avoid off-site accumulation and uptake by target immune cells in tumors. Using the 4T1 mouse model of metastatic breast cancer and flow cytometry, it was determined that the degree of PEGylation significantly influenced the uptake of 'empty' MSNs by tumor-resident innate immune cells. This was not the case for the agonist-loaded immuno-MSN variants. It should be noted the surface charge of the 'empty' MSNs was positive rather than neutral for the agonist-loaded immuno-MSNs. However, even though the cellular uptake was similar at 24 h after injection for the three immuno-MSN variants, we observed a significant beneficial effect on the activation and expansion of APCs especially in lung metastasis using the lightly PEGylated immuno-MSN variant.

Size-Controlled and Shelf-Stable DNA Particles for Production of Lentiviral Vectors

Polyelectrolyte complex particles assembled from plasmid DNA (pDNA) and poly(ethylenimine) (PEI) have been widely used to produce lentiviral vectors (LVVs) for gene therapy. The current batch-mode preparation for pDNA/PEI particles presents limited reproducibility in large-scale LVV manufacturing processes, leading to challenges in tightly controlling particle stability, transfection outcomes, and LVV production yield. Here we identified the size of pDNA/PEI particles as a key determinant for a high transfection efficiency with an optimal size of 400-500 nm, due to a cellular-uptake-related mechanism. We developed a kinetics-based approach to assemble size-controlled and shelf-stable particles using preassembled nanoparticles as building blocks and demonstrated production scalability on a scale of at least 100 mL. The preservation of colloidal stability and transfection efficiency was benchmarked against particles generated using an industry standard protocol. This particle manufacturing method effectively streamlines the viral manufacturing process and improves the production quality and consistency.

Mimicking natural strategies to create multi-environment enzymatic reactors: From natural cell compartments to artificial polyelectrolyte reactors

Engineering microenvironments for sequential enzymatic reactions has attracted specific interest within different fields of research as an effective strategy to improve the catalytic performance of enzymes. While in industry most enzymatic reactions occur in a single compartment carrier, living cells are however able to conduct multiple reactions simultaneously within confined sub-compartments, or organelles. Engineering multi-compartments with regulated environments and transformation properties enhances enzyme activity and stability and thus increases the overall yield of final products. In this review, we discuss current and potential methods to fabricate artificial cells for sequential enzymatic reactions, which are inspired by mechanisms and metabolic pathways developed by living cells. We aim to advance the understanding of living cell complexity and its compartmentalization and present solutions to mimic these processes in vitro. Particular attention has been given to layer-by-layer assembly of polyelectrolytes for developing multi-compartments. We hope this review paves the way for the next steps toward engineering of smart artificial multi-compartments with adoptive stimuli-responsive properties, mimicking living cells to improve catalytic properties and efficiency of the enzymes and enhance their stability.

Polymeric Delivery of Therapeutic Nucleic Acids

The advent of genome editing has transformed the therapeutic landscape for several debilitating diseases, and the clinical outlook for gene therapeutics has never been more promising. The therapeutic potential of nucleic acids has been limited by a reliance on engineered viral vectors for delivery. Chemically defined polymers can remediate technological, regulatory, and clinical challenges associated with viral modes of gene delivery. Because of their scalability, versatility, and exquisite tunability, polymers are ideal biomaterial platforms for delivering nucleic acid payloads efficiently while minimizing immune response and cellular toxicity. While polymeric gene delivery has progressed significantly in the past four decades, clinical translation of polymeric vehicles faces several formidable challenges. The aim of our Account is to illustrate diverse concepts in designing polymeric vectors towards meeting therapeutic goals of in vivo and ex vivo gene therapy. Here, we highlight several classes of polymers employed in gene delivery and summarize the recent work on understanding the contributions of chemical and architectural design parameters. We touch upon characterization methods used to visualize and understand events transpiring at the interfaces between polymer, nucleic acids, and the physiological environment. We conclude that interdisciplinary approaches and methodologies motivated by fundamental questions are key to designing high-performing polymeric vehicles for gene therapy.

Chemically Triggered Coalescence and Reactivity of Droplet Fibers

We describe the role of functional polymer surfactants in the construction and triggered collapse of droplet-based fibers and the use of these macroscopic supracolloidal structures for reagent compartmentalization. Copolymer surfactants containing both zwitterionic and tertiary amine pendent groups were synthesized for stabilization of oil-in-water droplets, in which the self-adherent properties of the selected zwitterions impart interdroplet adherence, while the amine groups provide access to pH-triggered coalescence. Macroscopic fibers, obtained by droplet extrusion, were prepared with reagents embedded in spatially distinct components of the fibers. Upon acidification of the continuous aqueous phase, protonation of the polymer surfactants increases their hydrophilicity and causes rapid fiber disruption and collapse. Cross-linked versions of these supracolloidal fibers were stable upon acidification and appeared to direct interdroplet passage of encapsulants along the fiber length. Overall, these functional, responsive emulsions provide a strategy to impart on-demand chemical reactivity to soft materials structures that benefits from the interfacial chemistry of the system.

Gold-seeded Lithium Niobate Nanoparticles: Influence of Gold Surface Coverage on Second Harmonic Properties

Hybrid nanoparticles composed of an efficient nonlinear optical core and a gold shell can enhance and tune the nonlinear optical emission thanks to the plasmonic effect. However the influence of an incomplete gold shell, i.e., isolated gold nano-islands, is still not well studied. Here LiNbO₃ (LN) core nanoparticles of 45 nm were coated with various densities of gold nano-seeds (AuSeeds). As both LN and AuSeeds bear negative surface charge, a positively-charged polymer was first coated onto LN. The number of polymer chains per LN was evaluated at 1210 by XPS and confirmed by fluorescence titration. Then, the surface coverage percentage of AuSeeds onto LN was estimated to a maximum of 30% using ICP-AES. The addition of AuSeeds was also accompanied with surface charge reversal, the negative charge increasing with the higher amount of AuSeeds. Finally, the first hyperpolarizability decreased with the increase of AuSeeds density while depolarization values for Au-seeded LN were close to the one of bare LN, showing a predominance of the second harmonic volumic contribution.

A Simple Distance Paper-Based Analytical Device for the Screening of Lead in Food Matrices

A simple and rapid distance paper-based analytical device (dPAD) for the detection of lead (Pb) in foods is proposed herein. The assay principle is based on competitive binding between carminic acid (CA) and polyethyleneimine (PEI) to Pb in a food sample. The paper channels were pre-immobilized with PEI, before reacting with a mixture of the sample and CA. Pb can strongly bind to the CA; hence, the length of the red color deposition on the flow channel decreased as a lower amount of free CA bound to PEI. The dPAD exhibited good linear correlation, with ranges of 5-100 µg·mL-1 (R2 = 0.974) of Pb. Although, the limit of detection (LOD) of this platform was rather high, at 12.3 µg·mL-1, a series of standard additions (8.0, 9.0, and 10.0 µg·mL-1) can be used to interpret the cutoff of Pb concentrations at higher or lower than 2 µg·mL-1. The presence of common metal ions such as calcium, magnesium, nickel, and zinc did not interfere with the color distance readout. The validity of the developed dPAD was demonstrated by its applicability to screen the contamination of Pb in century egg samples. The results obtained from the dPAD are in accordance with the concentration measured by atomic absorption spectroscopy (AAS) (n = 9). In conclusion, this proposed dPAD, combined with the standard addition method, could be applied for screening Pb contamination in food matrices. This platform is, therefore, potentially applicable for field measurements of Pb in developing countries, because it is cheap and rapid, and it requires no significant laborious instruments.

Surface modification of silica nanoparticles by hexarhenium anionic cluster complexes for pH-sensing and staining of cell nuclei

The surface deposition of luminescent anionic cluster complex [{Re₆S₈}(OH)₆]^4- advantages to the design and synthesis of composite luminescent silica nanoparticles (SNs) for intracellular imaging and sensing, while the encapsulation of the cluster units into SNs lacks for efficient luminescence. The deposition of the Re₆ clusters resulted from their assembly at the silica surface functionalized by amino-groups provides the synthetic route for the composite SNs with bright cluster-centered luminescence invariable in pH range from 4.0 to 12.0. The pH-dependent supramolecular assembly of the cluster units with polyethyleneimine (PEI) at the silica surface is an alternative route for the synthesis of the composite SNs with high cluster-centered luminescence sensitive to pH-changes within 4.0-6.0. The sensitivity derives from the pH-driven conformational changes of PEI chains resulting in the release of the clusters from the PEI-based confinement under the acidification within pH 6.0-4.0. The potential of the composite SNs in cellular contrasting has been also revealed by the cell viability and flow cytometry measurements. It has been found that the PEI-supported embedding of the cluster units facilitates cell internalization of the composite SNs as well as results in specific intracellular distribution manifested by efficient staining of the cell nuclei in the confocal images.

Method for efficient soluble expression and purification of recombinant hyperactive Tn5 transposase

Efficient preparation of libraries is the key step of next-generation sequencing (NGS) methods. Tn5 transposase enables simple, robust and highly efficient tagmentation-based library construction. Here, we report a simple and reliable expression and purification strategy based on fusing Tn5 to the small B1 immunoglobulin binding domain of Streptococcal protein G (GB1) and high affinity 10× His tag. The purified recombinant Tn5 showed high DNA tagmentation activity and ultra-low nucleic acid contamination. This method greatly cuts the costs of Tn5-based NGS library construction and is beneficial to the development of new NGS methods.

Interaction of hairy carboxyalkyl cellulose nanocrystals with cationic surfactant: Effect of carbon spacer

Tuning the surface chemistry of nanocellulose is essential for developing its end-use applications. Herein, different carboxyalkylated cellulose nanocrystals (CNC) with similar charge densities but with tunable hairy structures were produced. The effect of carbon spacer of the grafted groups on the interaction of the CNC and a cationic surfactant, myristyl trimethyl ammonium bromide (MTAB), at different pH and salinity was explored. The CNC with longer grafted chain length was more hydrophobic, adsorbed more MTAB, and formed a more compact MTAB adlayer than did CNC with the shorter chain length. Also, the adsorption was higher at neutral pH, implying a high electrostatic attraction and hydrophobic interaction between substrates. The hydrophobic interaction of MTAB and hairy CNC in saline systems improved its adsorption. Although MTAB adsorbed more when its concentration was higher than its critical micelle concentration (CMC), the adsorbed adlayer had a less compact structure on the CNC surfaces.

Pre- and Post-Transcriptional Regulation of cFLIP for Effective Cancer Therapy Using pH-Ultrasensitive Nanoparticles

Cellular FLIP (cFLIP) is a crucial player of apoptosis-regulated pathways that is frequently overexpressed in solid cancers. To inhibit c-FLIP, pre- and post-transcriptionally, a multifunctional nanoparticle (NP) was created to deliver cFLIP-specific small interfering RNA (siRNA) into cancer cells. Specifically, Vorinostat (Vor)-loaded mesoporous silica nanoparticles (MSN) were conjugated with polyethylenimine-biotin (PB), followed by electrostatically binding with cFLIP siRNA (Vor/siR@MSN-PB). To stabilize and prolong the circulation time of nanoparticles, a bialdehyde-modified poly(ethylene glycol) (PEG) was cross-linked onto the polyethylenimine (PEI) backbone via the formation of the imine linkage (Schiff base) (Vor/siR@MSN-PB-PEG). The Schiff base is highly stable at physiological pH 7.4 but labile under slightly acidic pH conditions. In the acidic tumor microenvironment (TME), the PEG outer layer could be rapidly cleaved, resulting in the switching of the nanoparticle surface charge to positive, which specifically enhances internalization of the NPs to the biotin-positive tumor cells. Our results demonstrated the successful preparation of Vor/siR@MSN-PB-PEG NPs, in which the siRNA was effectively protected in serum and regulated the expression of cFlip, post-transcriptionally. The presence of the PEG layer resulted in high tumor accumulation and high efficacy in tumor inhibition, which was a result of the efficient cFLIP suppression. Furthermore, in the low-dose regimen of Vorinostat-the pre-transcriptional cFLIP suppressor, treatment with Vor/siR@MSN-PB-PEG NPs was found to be safe with the treated mice, indicating a promising combination regimen for cancer therapy.

Carbapenem-Resistant Klebsiella pneumoniae Clinical Isolates: In Vivo Virulence Assessment in Galleria mellonella and Potential Therapeutics by Polycationic Oligoethyleneimine

Klebsiella pneumoniae, one of the most common pathogens found in hospital-acquired infections, is often resistant to multiple antibiotics. In fact, multidrug-resistant (MDR) K. pneumoniae producing KPC or OXA-48-like carbapenemases are recognized as a serious global health threat. In this sense, we evaluated the virulence of K. pneumoniae KPC(+) or OXA-48(+) aiming at potential antimicrobial therapeutics. K. pneumoniae carbapenemase (KPC) and the expanded-spectrum oxacillinase OXA-48 isolates were obtained from patients treated in medical care units in Lisbon, Portugal. The virulence potential of the K. pneumonia clinical isolates was tested using the Galleria mellonella model. For that, G. mellonella larvae were inoculated using patients KPC(+) and OXA-48(+) isolates. Using this in vivo model, the KPC(+) K. pneumoniae isolates showed to be, on average, more virulent than OXA-48(+). Virulence was found attenuated when a low bacterial inoculum (one magnitude lower) was tested. In addition, we also report the use of a synthetic polycationic oligomer (L-OEI-h) as a potential antimicrobial agent to fight infectious diseases caused by MDR bacteria. L-OEI-h has a broad-spectrum antibacterial activity and exerts a significantly bactericidal activity within the first 5-30 min treatment, causing lysis of the cytoplasmic membrane. Importantly, the polycationic oligomer showed low toxicity against in vitro models and no visible cytotoxicity (measured by survival and health index) was noted on the in vivo model (G. mellonella), thus L-OEI-h is foreseen as a promising polymer therapeutic for the treatment of MDR K. pneumoniae infections.

Graphene oxide chemically reduced and functionalized with KOH-PEI for efficient Cr(VI) adsorption and reduction in acidic medium

In this study, graphene oxide (GO), polyethyleneimine (PEI) and potassium hydroxide (KOH) were used to synthesize reduced graphene oxide (rGO/PEI-KOH) nanocomposite. The presence and grafting of PEI molecules on the reduced GO surface were assessed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) analyses. The rGO/PEI-KOH nanocomposite was successfully applied for hexavalent chromium, Cr(VI), wastewater elimination. The resulting rGO/PEI-KOH adsorbent was found to be highly effective for Cr(VI) removal at low pH values and achieved a maximum capacity of experimental adsorption of 398.9 mg/g, which is one of the highest sorption capacity of most GO- and PEI-based adsorbents reported in the literature up to date. Studying the adsorption mechanism, the sorption isotherm revealed that the modified-Langmuir model was the best fit and Cr(VI) removal follows a pseudo-second-order kinetics, with the predominance of intraparticle diffusion during the first step of adsorption. XPS analysis indicated the presence of appreciable amount of Cr(III) on the adsorbent surface, which suggests that the adsorbed Cr(VI) ions were effectively reduced to Cr(III) on the rGO/PEI-KOH adsorbent surface (∼70% of the total adsorbed Cr). Cr(VI) adsorption and subsequent reduction to Cr(III) both contributed to the Cr(VI) removal. The results of the present study highlight the benefits of rGO/PEI-KOH like low cost, environmentally friendly, large toxic Cr(VI) ions adsorption capacity and its effective reduction to less-toxic Cr(III).

Metabolite-Based Modification of Poly(l-lysine) for Improved Gene Delivery

Synthetic gene delivery systems employ multiple functions to enable safe and effective transport of DNA to target cells. Here, we describe metabolite-based poly(l-lysine) (PLL) modifiers that improve transfection by imparting both pH buffering and nanoparticle stabilization functions within a single molecular unit. PLL modifiers were based on morpholine (M), morpholine and niacin (MN), or thiomorpholine (TM). PLL modification with (MN) or (TM) imparted buffering function over the pH range of 5-7 both in solution and live cells and enhanced the stability of PLL DNA nanoparticles, which exhibited higher resistance to polyanion exchange and prolonged blood circulation. These properties translated into increased transfection efficiency in vitro coupled with reduced toxicity compared to unmodified PLL and PLL(M). Furthermore, PEG-PLL(MN) DNA nanoparticles transfected muscle tissue in vivo for >45 days following intramuscular injection. These polymer modifiers demonstrate the successful design of multifunctional units that improve transfection of synthetic gene delivery systems while maintaining biocompatibility.

Probing the Molecular Structure of Coadsorbed Polyethylenimine and Charged Surfactants at the Nanoemulsion Droplet Surface

Nanoemulsions, nanoscale oil droplets dispersed in an aqueous medium, can be stabilized by polymer-surfactant (PS) mixtures, making them ubiquitous in commercial, industrial, and pharmaceutical applications. It is well-known that the presence of PS layers coadsorbed at the droplet surface plays a significant role in droplet stability and functionality; however, little is understood about the molecular nature of this coadsorption. Such insights are especially important for application in drug delivery where physiological conditions can vary the environmental pH and significantly impact stabilization. Hence, the focus of this study examines the surface properties of ∼300 nm nanoemulsions stabilized by the coadsorption of polyethylenimine (PEI) and charged alkyl surfactants sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium bromide (DTAB). PEI is a common charge-tunable polymer used in nanocarrier templates. This study employs vibrational sum frequency scattering spectroscopy, coupled with ζ-potential and surface pressure measurements performed as a function of varying concentrations and pH. The surface specific spectroscopic results reported herein reveal that PEI adsorption and molecular ordering is influenced by both electrostatic and hydrophobic interactions. While the degree of PEI adsorption is stronger in the presence of anionic SDS than cationic DTAB, for both surfactants, PEI is molecularly disordered in acidic conditions and adopts a persistent net ordering as the solution pH becomes more basic. Both surfactants also display degrees of interfacial conformational ordering that is altered by the presence of the coadsorbed polymer. These results demonstrate the molecular-level diversity in PEI behavior at the droplet interface and provide insight into how such behavior can be controlled to yield nanocarrier technology with specific functions and enhanced efficacy.