Highly Branched Polymers Based on Poly(amino acid)s for Biomedical Application

Recent Advances in Degradable Biomedical Polymers for Prevention, Diagnosis and Treatment of Diseases

Biomedical polymers play a key role in preventing, diagnosing, and treating diseases, showcasing a wide range of applications. Their unique advantages, such as rich source, good biocompatibility, and excellent modifiability, make them ideal biomaterials for drug delivery, biomedical imaging, and tissue engineering. However, conventional biomedical polymers suffer from poor degradation in vivo, increasing the risks of bioaccumulation and potential toxicity. To address these issues, degradable biomedical polymers can serve as an alternative strategy in biomedicine. Degradable biomedical polymers can efficiently relieve bioaccumulation in vivo and effectively reduce patient burden in disease management. This review comprehensively introduces the classification and properties of biomedical polymers and the recent research progress of degradable biomedical polymers in various diseases. Through an in-depth analysis of their classification, properties, and applications, we aim to provide strong guidance for promoting basic research and clinical translation of degradable biomedical polymers.

Aromatic poly (amino acids) as an effective low-temperature demulsifier for treating crude oil-in-water emulsions

Amphiphilic aromatic poly (amino acids) polymers were designed as biodegradability demulsifiers with higher aromaticity, stronger polarity, and side chain-like combs. The effects of demulsifier dosage, structural characteristics and emulsion properties such as pH, salinity, and oil content on the demulsification efficiency were investigated. The results show that the poly (L-glutamic-benzyl ester)-block-poly (L-phenylalanine) (PBLG15-b-PPA15) as the demulsifier can remove more than 99.97% of the oil in a 5.0 wt% oil-in-water (O/W) emulsion at room temperature within 2 min. The poly (L-tyrosine)-block-poly (L-phenylalanine) (PTyr15-b-PPA15) with environmental durability demonstrates high effectiveness, universality, and demulsification speed. It achieves a remarkable demulsification efficiency of up to 99.99% for a 20.0 wt% O/W emulsion at room temperature. The demulsification mechanism indicates that demulsifiers have sufficient interfacial activity can quickly migrate to the oil-water interface after being added to the emulsions. Additionally, when demulsifiers are present in a continuous phase in the molecular form, their "teeth" side chains are beneficial for increasing coalescence and flocculation capacities. Furthermore, according to the Density Functional Theory (DFT) calculations, enhancing the intermolecular interactions between demulsifiers and the primary native surfactants that form an oil-water interfacial film is a more efficient approach to reducing demulsification temperature and improving demulsification efficiency and rate.

A Theoretical Investigation of the Polyaddition of an AB2+A2+B4 Monomer Mixture

Hyperbranched polymers (HBPs) are widely applied nowadays as functional materials for biomedicine needs, nonlinear optics, organic semiconductors, etc. One of the effective and promising ways to synthesize HBPs is a polyaddition of AB2+A2+B4 monomers that is generated in the A2+CB2, AA'+B3, A2+B'B2, and A2+C2+B3 systems or using other approaches. It is clear that all the foundational features of HBPs that are manufactured by a polyaddition reaction are defined by the component composition of the monomer mixture. For this reason, we have designed a structural kinetic model of AB2+A2+B4 monomer mixture polyaddition which makes it possible to predict the impact of the monomer mixture's composition on the molecular weight characteristics of hyperbranched polymers (number average (DPn) and weight average (DPw) degree of polymerization), as well as the degree of branching (DB) and gel point (pg). The suggested model also considers the possibility of a positive or negative substitution effect during polyaddition. The change in the macromolecule parameters of HBPs formed by polyaddition of AB2+A2+B4 monomers is described as an infinite system of kinetic equations. The solution for the equation system was found using the method of generating functions. The impact of both the component's composition and the substitution effect during the polyaddition of AB2+A2+B4 monomers on structural and molecular weight HBP characteristics was investigated. The suggested model is fairly versatile; it makes it possible to describe every possible case of polyaddition with various monomer combinations, such as A2+AB2, AB2+B4, AB2, or A2+B4. The influence of each monomer type on the main characteristics of hyperbranched polymers that are obtained by the polyaddition of AB2+A2+B4 monomers has been investigated. Based on the results obtained, an empirical formula was proposed to estimate the pg = pA during the polyaddition of an AB2+A2+B4 monomer mixture: pg = pA = (-0.53([B]0/[A]0)1/2 + 0.78)υAB2 + (1/3)1/2([B]0/[A]0)1/2, where (1/3)1/2([B]0/[A]0)1/2 is the Flory equation for the A2+B4 polyaddition, [A]0 and [B]0 are the A and B group concentration from A2 and B4, respectively, and υAB2 is the mole fraction of the AB2 monomer in the mixture. The equation obtained allows us to accurately predict the pg value, with an AB2 monomer content of up to 80%.

Polypeptide-Based Systems: From Synthesis to Application in Drug Delivery

Synthetic polypeptides are biocompatible and biodegradable macromolecules whose composition and architecture can vary over a wide range. Their unique ability to form secondary structures, as well as different pathways of modification and biofunctionalization due to the diversity of amino acids, provide variation in the physicochemical and biological properties of polypeptide-containing materials. In this review article, we summarize the advances in the synthesis of polypeptides and their copolymers and the application of these systems for drug delivery in the form of (nano)particles or hydrogels. The issues, such as the diversity of polypeptide-containing (nano)particle types, the methods for their preparation and drug loading, as well as the influence of physicochemical characteristics on stability, degradability, cellular uptake, cytotoxicity, hemolysis, and immunogenicity of polypeptide-containing nanoparticles and their drug formulations, are comprehensively discussed. Finally, recent advances in the development of certain drug nanoformulations for peptides, proteins, gene delivery, cancer therapy, and antimicrobial and anti-inflammatory systems are summarized.

Morphological Evaluation of Supramolecular Soft Materials Obtained through Co-Assembly Processes

Low-molecular-weight gelators (LMWGs) are compounds with an intrinsic tendency to self-assemble forming various supramolecular architectures via non-covalent interactions. Considering that the development of supramolecular assemblies through the synergy of molecules is not entirely understood at the molecular level, this study introduced a Fmoc-short peptide and four Fmoc-amino acids as building blocks for the self-assembly/co-assembly process. Hence, we investigated the formation of supramolecular gels starting from the molecular aggregation following two triggering approaches: solvent/co-solvent method and pH switch. The complex morphological analysis (POM, AFM, and STEM) offered an insight into the spontaneous formation of well-ordered nanoaggregates. Briefly, POM and AFM images demonstrated that self-assembled gels present various morphologies like dendrimer, spherulite, and vesicle, whereas all co-assembled supramolecular systems exhibit fibrillar morphologies as a result of the interaction between co-partners of each system. STEM study has confirmed that the molecules interact and join together, finally forming a fibrous network, an aspect seen in both self-assembled and co-assembled gels. XRD allowed the determination of the molecular arrangement. The study emphasized that the Fmoc motif protected the amino groups and facilitated gelation through additional π-π interactions.

An immune-enhanced multivalent DNA nanovaccine to prevent H7 and H9 avian influenza virus in mice

H7 avian influenza virus has caused multiple human infections and poses a severe public health threat. In response to the highly variable nature of AIVs, a novel, easily regenerated DNA vaccine has great potential in treating or preventing avian influenza pandemics. Nevertheless, DNA vaccines have many disadvantages, such as weak immunogenicity and poor in vivo delivery. To further characterize and solve these issues and develop a novel H7 AIV DNA vaccine with enhanced stability and immunogenicity, we constructed nine AIV DNA plasmids, and the immunogenicity screened showed that mice immunized with pβH7N2SH9 elicited stronger hemagglutination-inhibiting (HI) antibodies than other eight plasmid DNAs. Then, to address the susceptibility to degradation and low transfection rate of DNA vaccine in vivo, we developed pβH7N2SH9/DGL NPs by encapsulating the pβH7N2SH9 within the dendrigraft poly-l-lysines nanoparticles. As expected, these NPs exhibited excellent physical and chemical properties, were capable of promote lymphocyte proliferation, and induce stronger humoral and cellular responses than the naked pβH7N2SH9, including higher levels of HI antibodies than naked pβH7N2SH9, as well as the production of cytokines, namely, IL-2, IFN-α. Taken together, our results suggest that the construction of an immune-enhanced H7-AIV DNA nanovaccine may be a promising strategy against most influenza viruses.

Next Generation Mucosal Vaccine Strategy for Respiratory Pathogens

Inducing humoral and cytotoxic mucosal immunity at the sites of pathogen entry has the potential to prevent the infection from getting established. This is different from systemic vaccination, which protects against the development of systemic symptoms. The field of mucosal vaccination has seen fewer technological advances compared to nucleic acid and subunit vaccine advances for injectable vaccine platforms. The advent of the next-generation adenoviral vectors has given a boost to mucosal vaccine research. Basic research into the mechanisms regulating innate and adaptive mucosal immunity and the discovery of effective and safe mucosal vaccine adjuvants will continue to improve mucosal vaccine design. The results from clinical trials of inhaled COVID-19 vaccines demonstrate their ability to induce the proliferation of cytotoxic T cells and the production of secreted IgA and IgG antibodies locally, unlike intramuscular vaccinations. However, these mucosal vaccines induce systemic immune responses at par with systemic vaccinations. This review summarizes the function of the respiratory mucosa-associated lymphoid tissue and the advantages that the adenoviral vectors provide as inhaled vaccine platforms.

Enhance immune response to H9 AIV DNA vaccine based on polygene expression and DGL nanoparticle encapsulation

DNA vaccination has great potential to treat or prevent avian influenza pandemics, but the technique may be limited by low immunogenicity and gene delivery in clinical testing. Here, to improve the immune efficacy of DNA vaccines against avian influenza, we prepared and tested the immunogenicity of 4 recombinant DNA vaccines containing 2 or 3 AIV antigens. The results revealed that chickens and mice immunized with plasmid DNA containing 3 antigens (HA gene from H9N2, and NA and HA genes from H5N1) exhibited a robust immune response than chickens and mice immunized with plasmid DNAs containing 2 antigenic genes. Subsequently, this study used pβH9N1SH5 as a model antigen to study the effect of dendritic polylysine (DGL) nanoparticles as a gene delivery system and adjuvant on antigen-specific immunity in mice models. At a ratio of 1:3 DGL/pβH9N1SH5 (w/w), the pβH9N1SH5/DGL NPs showed excellent physical and chemical properties, induced higher levels of HI antibodies, and larger CD3+/CD4+ T lymphocyte and CD3+/CD8+ T lymphocyte population, as well as the production of cytokines, namely, interferon (IFN)-γ, interleukin (IL)-2 compared with the naked pβH9N1SH5. Therefore, multiantigen gene expression methods using DGL as a delivery system may have broad application prospects in gene therapy.

Nanoparticle delivery of TFOs is a novel targeted therapy for HER2 amplified breast cancer

PURPOSE

The human EGFR2 (HER2) signaling pathway is one of the most actively studied targets in cancer transformation research. Ttriplex-forming oligonucleotides (TFOs) activate DNA damage and induce apoptosis. We aim to encapsulate TFO-HER2 with nano-particle ZW-128 to suppress breast cell growth in vitro and in vivo.

EXPERIMENTAL DESIGN

We designed a set of TFO fragments targeting HER2 and verified their effectiveness. We encapsulated TFO-HER2 in ZW-128 to form nano-drug TFO@ZW-128. Cell counting kit 8, flow cytometry, and western blotting were used to evaluate the effect of TFO@ZW-128 on cell proliferation and the expressions of related proteins. The ant-itumor effect of TFO@ZW-128 was evaluated in vivo using nude mice breast cancer model.

RESULTS

TFO@ZW-128 had efficient cellular uptake in amplified HER2 breast cancer cells. TFO@ZW-128 showed an 80-fold increase in TFO utilization compared with TFO-HER2 in the nude mouse breast cancer model. Meanwhile, TFO@ZW-128 dramatically inhibited the growth of HER2-overexpressing tumors compared with TFO-HER2 (P < 0.05). Furthermore, TFO@ZW-128-induced cell apoptosis was in a p53-independent manner.

CONCLUSIONS

In this study, we designed nano-drug TFO@ZW-128, which has proven effective and non-toxic in targeted therapy for ectopic HER2-expressing tumors.

Novel Multi-Responsive Hyperbranched Polyelectrolyte Polyplexes as Potential Gene Delivery Vectors

In this work, we investigate the complexation behavior of poly(oligo(ethylene glycol)methyl methacrylate)-co-poly(2-(diisopropylamino)ethyl methacrylate), P(OEGMA-co-DIPAEMA), hyperbranched polyelectrolyte copolymers, synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization, with short-linear DNA molecules. The synthesized hyperbranched copolymers (HBC), having a different chemical composition, are prepared in order to study their ability to bind with a linear nucleic acid at various N/P ratios (amine over phosphate groups). Specifically, the three pH and thermo-responsive P(OEGMA-co-DIPAEMA) hyperbranched copolymers were able to form polyplexes with DNA, with dimensions in the nanoscale. Using several physicochemical methods, such as dynamic and electrophoretic light scattering (DLS, ELS), as well as fluorescence spectroscopy (FS), the complexation process and the properties of formed polyplexes were explored in response to physical and chemical stimuli such as temperature, pH, and ionic strength. The mass and the size of polyplexes are shown to be affected by the hydrophobicity of the copolymer utilized each time, as well as the N/P ratio. Additionally, the stability of polyplexes in the presence of serum proteins is found to be excellent. Finally, the multi-responsive hyperbranched copolymers were evaluated regarding their cytotoxicity via in vitro experiments on HEK 293 non-cancerous cell lines and found to be sufficiently non-toxic. Based on our results, these polyplexes could be useful candidates for gene delivery and related biomedical applications.

Construction of poly(amino acid)s nano-delivery system and sustained release with redox-responsive

A series of novel poly(amino acid)s materials were designed to prepare drug-loaded nanoparticles by physical encapsulation and chemical bonding. The side chain of the polymer contains a large number of amino groups, which effectively increases the loading rate of doxorubicin (DOX). The structure contains disulfide bonds that showing a strong response to the redox environment, which can achieve targeted drug release in the tumor microenvironment. Nanoparticles mainly present spherical morphology with the suitable size for participating in systemic circulation. cell experiments demonstrate the non-toxicity and good cellular uptake behavior of polymers. In vivo anti-tumor experiments shows nanoparticles could inhibit tumor growth and effectively reduce the side effects of DOX.

Dendrimer: An update on recent developments and future opportunities for the brain tumors diagnosis and treatment

A brain tumor is an uncontrolled cell proliferation, a mass of tissue composed of cells that grow and divide abnormally and appear to be uncontrollable by the processes that normally control normal cells. Approximately 25,690 primary malignant brain tumors are discovered each year, 70% of which originate in glial cells. It has been observed that the blood-brain barrier (BBB) limits the distribution of drugs into the tumour environment, which complicates the oncological therapy of malignant brain tumours. Numerous studies have found that nanocarriers have demonstrated significant therapeutic efficacy in brain diseases. This review, based on a non-systematic search of the existing literature, provides an update on the existing knowledge of the types of dendrimers, synthesis methods, and mechanisms of action in relation to brain tumours. It also discusses the use of dendrimers in the diagnosis and treatment of brain tumours and the future possibilities of dendrimers. Dendrimers are of particular interest in the diagnosis and treatment of brain tumours because they can transport biochemical agents across the BBB to the tumour and into the brain after systemic administration. Dendrimers are being used to develop novel therapeutics such as prolonged release of drugs, immunotherapy, and antineoplastic effects. The use of PAMAM, PPI, PLL and surface engineered dendrimers has proven revolutionary in the effective diagnosis and treatment of brain tumours.

Amphiphilic Polypeptides Obtained by the Post-Polymerization Modification of Poly(Glutamic Acid) and Their Evaluation as Delivery Systems for Hydrophobic Drugs

Synthetic poly(amino acids) are a unique class of macromolecules imitating natural polypeptides and are widely considered as carriers for drug and gene delivery. In this work, we synthesized, characterized and studied the properties of amphiphilic copolymers obtained by the post-polymerization modification of poly(α,L-glutamic acid) with various hydrophobic and basic L-amino acids and D-glucosamine. The resulting glycopolypeptides were capable of forming nanoparticles that exhibited reduced macrophage uptake and were non-toxic to human lung epithelial cells (BEAS-2B). Moreover, the developed nanoparticles were suitable for loading hydrophobic cargo. In particular, paclitaxel nanoformulations had a size of 170-330 nm and demonstrated a high cytostatic efficacy against human lung adenocarcinoma (A549). In general, the obtained nanoparticles were comparable in terms of their characteristics and properties to those based on amphiphilic (glyco)polypeptides obtained by copolymerization methods.

Modulating the poly-L-lysine structure through the control of the protonation-deprotonation state of L-lysine

Designing the architecture of L-lysine-based polymeric structures is a highly challenging task that requires careful control of the amino acid reactive groups. Conventional processes to obtain branched polylysine need several steps and the addition of specific catalysts. In the present work, to gain a better understanding and control of the formation of L-lysine-based polymers, we have investigated the correlation between the protonation state of L-lysine and the corresponding hydrothermally grown structures. The samples have been characterized by combining optical spectroscopies, such as UV-Vis, fluorescence, and synchrotron radiation circular dichroism with structural analysis by Nuclear Magnetic Resonance, Fourier Transform Infrared spectroscopy, and dynamic light scattering. We have observed that aqueous precursor solutions with alkaline pHs promote the formation of branched structures. In contrast, high pHs favour the reactivity of the ε-amino groups leading to linear structures, as shown by circular dichroism analyses. On the other hand, acidic conditions trigger the branching of the amino acid. Interestingly, the polymeric forms of L-lysine emit in the blue because the increasing number of intermolecular hydrogen bonds promote the intermolecular charge transfer responsible for the emission. Understanding the correlation between the L-lysine charged states and the polymeric structures that could form controlling the protonation-deprotonation states of the amino acid opens the route to a refined design of polypeptide systems based on L-lysine.

Influence of cationic groups on the antibacterial behavior of cationic nano-sized hyperbranched polymers to enhance bacteria-infected wound healing

With the continuous emergence of drug-resistant pathogens, new strategies with high antibacterial efficacy are urgently needed. Herein, five cationic nano-sized hyperbranched polymers (CNHBPs) with cationic functional groups have been constructed, and their antibacterial mechanism has been studied in detail. CNHBPs bearing secondary ammonium salt groups and long alkyl chains (S₁₂-CNHBP) exhibited weak antibacterial and antibiofilm ability, while CNHBPs bearing quaternary ammonium salt groups and long alkyl chains (Q₁₂-CNHBP) showed the highest antimicrobial and strongest antibiofilm activities. ζ potential and isothermal titration microcalorimetry (ITC) results suggest that the negatively charged surfaces of bacterial cells provided Q₁₂-CNHBP with a higher intrinsic electrostatic driving force for bacterial killing than that with S₁₂-CNHBP. Fluorescent tracing and morphological observations indicate that the bacterial genome might be another antibacterial target for S₁₂-CNHBP in addition to the cell wall and membrane, which are mainly antibacterial targets for Q₁₂-CNHBP, making it less likely to induce bacterial resistance. Surprisingly, Q₁₂-CNHBP exhibited superior in vivo therapeutic efficacy in a mouse wound model of methicillin-resistant Staphylococcus aureus (MRSA) infection with low toxicity during treatment. These advantages and ease of preparation will undoubtedly distinguish Q₁₂-CNHBP as a new class of suitable candidates to combat multidrug-resistant pathogen infections. This study opens up a new avenue for exploiting antibacterial biomaterials to treat infections caused by drug-resistant bacteria.

New Fmoc-Amino Acids/Peptides-Based Supramolecular Gels Obtained through Co-Assembly Process: Preparation and Characterization

One of the methods of obtaining supramolecular gels consists of the possibility of self-assembly of low molecular weight gelators (LMWGs). However, LMWG-based gels are often difficult to handle, easy to destroy and have poor rheological performance. In order to improve the gels’ properties, the LMWGs molecules are co-assembled, which induces more cross-links with more stable structures. Starting from these aspects, the present study refers to the preparation of a bionic hydrogel stabilized with a physiologically occurring, bifunctional biomolecule, L-lysine, co-assembled with other amino acids or peptides (such as a modified amino acid (Fmoc-serine or Fmoc-glutamic acid) or a tripeptide (Fmoc-Gly-Gly-Gly)) with the potential to support the repair of injuries or the age-related impaired structures or functions of living tissues. The introduction of a copartner aims to improve hydrogel characteristics from a morphological, rheological and structural point of view. On the other hand, the process will allow the understanding of the phenomenon of specific self-association and molecular recognition. Various characterization techniques were used to assess the ability to co-assemble: DLS, FT-IR, SEM and fluorescence microscopy, rheology and thermal analysis. Studies have confirmed that the supramolecular structure occurs through the formation of inter- and intramolecular physical bonds that ensure the formation of fibrils organized into 3D networks. The rheological data, namely the G′ > G″ and tan δ approximately 0.1−0.2 gel-like behavior observed for all studied samples, demonstrate and sustain the appearance of the co-assembly processes and the ability of the samples to act as LMWG. From the studied systems, the Fmoc−Lys−Fmoc_ Fmoc−Glu sample presented the best rheological characteristics that are consistent with the observations that resulted from the dichroism, fluorescence and SEM investigations.

Secondary Ammonium-Based Hyperbranched Poly(amidoamine) with Excellent Membrane-Active Property for Multidrug-Resistant Bacterial Infection

With the rapid emergence of microbial infections induced by "superbugs", public health and the global economy are threatened by the lack of effective and biocompatible antibacterial agents. Herein, we systematically design a series of secondary ammonium-based hyperbranched poly(amidoamine) (SAHBP) with different alkyl chain lengths for probing high-efficacy antibacterial agents. SAHBP modified with alkyl tails at the hyperbranched core could efficiently kill Escherichia coli and Staphylococcus aureus, two types of clinically important bacteria worldwide. The best SAHBP with 12-carbon-long alkyl tails (SAHBP-12) also showed high activity against problematic multidrug-resistant bacteria, including Pseudomonas aeruginosa and methicillin-resistant S. aureus (MRSA). Based on ζ potential, isothermal titration microcalorimetry (ITC), and membrane integrity assays, it is found that SAHBP-12 could attach to the cell membrane via electrostatic adsorption and hydrophobic interactions, following which the integrity of the bacterial cell wall and the cell membrane is disrupted, resulting in severe cell membrane damage and the leakage of cytoplasmic contents, finally causing bacterial cell death. Impressively, benefiting from excellent membrane-active property, SAHBP-12 exhibited robust therapeutic efficacy in MRSA-infected mice wounds. Moreover, SAHBP-12 also showed excellent biosafety in vitro and in vivo, which undoubtedly distinguished it as a potent weapon in combating the growing threat of problematic multidrug-resistant bacterial infections.

Blocking viral infections by Lysine-based polymeric nanostructures. A critical review

The outbreak of the Covid-19 pandemic due to the SARS-CoV-2 coronavirus has accelerated the search for innovative antivirals with possibly broad-spectrum efficacy. One of the possible strategies is to inhibit...

Triggered and monitored drug release from bifunctional hybrid nanocomposites

Polymer-coated carbon dot-containing calcium carbonate nanoparticles are reported as unique nanocomposites capable of encapsulating a chemotherapeutic drug and displaying afterglow behaviour.

A Guideline for the Synthesis of Amino-Acid-Functionalized Monomers and Their Polymerizations

Amino acids have emerged as a sustainable source for the design of functional polymers. Besides their wide availability, especially their high degree of biocompatibility makes them appealing for a broad range of applications in the biomedical research field. In addition to these favorable characteristics, the versatility of reactive functional groups in amino acids (i.e., carboxylic acids, amines, thiols, and hydroxyl groups) makes them suitable starting materials for various polymerization approaches, which include step- and chain-growth reactions. This review aims to provide an overview of strategies to incorporate amino acids into polymers. To this end, it focuses on the preparation of polymerizable monomers from amino acids, which yield main chain or side chain-functionalized polymers. Furthermore, postpolymerization modification approaches for polymer side chain functionalization are discussed. Amino acids are presented as a versatile platform for the development of polymers with tailored properties.