Search Results (69)

Background/Objectives: A nanostructured membrane of polycaprolactone (a synthetic polymer) was synthesized using an electrospinning technique aiming to enhance its hydrophilicity and rate of degradation by surface modification via aminolysis. Since polycaprolactone nanofibrous films are naturally hydrophobic and with slow degradation, which restricts their use in biological systems, amino groups were added to the fiber surface using the aminolysis technique, greatly increasing the wettability of the membranes. Methods: Polycaprolactone nanofibrous membranes were synthesized via the electrospinning technique and surface modification by aminolysis. Trypsin, pepsin, and pancreatin were conjugated onto the aminolyzed PNF surface to further strengthen biocompatibility by enhancing the hydrophilicity, porosity, and biodegradation rate. SEM, FTIR, EDX, and liquid displacement method were performed to investigate proteolytic efficiency and morphological and physical characteristics such as hydrophilicity, porosity, and degradation rates. Results: Enzyme activity tests, which showed a zone of clearance, validated the successful enzyme conjugation and stability over a wide range of pH and temperatures. Scanning electron microscopy (SEM) confirms the smooth morphology of nanofibers with diameters ranging from 150 to 950 nm. Fourier transform infrared spectroscopy (FTIR) revealed the presence of O–H, C–O, C=O, C–N, C–H, and O–H functional groups. Energy-dispersive X-ray (EDX) elemental analysis indicates the presence of carbon, oxygen, and nitrogen atoms owing to the presence of peptide and amide bonds. The liquid displacement technique and contact angle proved that Pepsin-PNFs possess notably increased porosity (88.50% ± 0.31%) and hydrophilicity (57.6° ± 2.3 (L), 57.9° ± 2.5 (R)), respectively. Pancreatin-PNFs demonstrated enhanced enzyme activity and degradation rate on day 28 (34.61%). Conclusions: These enzyme-conjugated PNFs thus show improvements in physicochemical properties, making them ideal candidates for various biomedical applications. Future studies must aim for optimization of enzyme conjugation and in vitro and in vivo performance to investigate the versatility of these scaffolds. Full article

Background/Objectives: Biodegradable polymers have emerged as promising platforms for drug delivery. Produced by microbiomes, polyhydroxyalkanoates (PHAs) offer excellent biocompatibility, biodegradability, and environmental sustainability. In this study, we report the surface functionalization of PHA-based nanoparticles (NPs) using the SpyTag–SpyCatcher system to enhance cellular uptake. Methods: Initial conjugation with mEGFP-SpyTag enabled visualization, followed by decoration with HER2-specific Affibody-SpyCatcher and/or TAT-SpyCatcher peptides. The prepared NPs retained a diameter of <200 nm and a negatively charged surface. Results: Affibody-functionalized NPs significantly enhanced internalization and cytotoxicity in HER2-overexpressing SK-BR-3 cells, whereas TAT-functionalized NPs promoted uptake across various cell types, independently of HER2 expression. Dual-functionalized NPs exhibited synergistic or attenuated effects based on the HER2 expression levels, highlighting the critical role of ligand composition in targeted delivery. Conclusions: The results of this study demonstrate that the SpyTag–SpyCatcher-mediated surface engineering of PHA NPs offers a modular and robust strategy for active targeting in nanomedicine. Full article

Polymer coatings as thin films stand out as a commonly used strategy to modify biosensor surfaces for improving detection performance; however, nonspecific biomolecule interactions and the limited degree of ligand conjugation on the surface have necessitated the development of innovative methods for surface modification. To this end, methacrylated tethered telechelic polyethylene glycol (PEG-diMA) chains of three different molecular weights (2, 6, and 10 kDa) were synthesized herein and used for obtaining thiolated nanoparticles (NPs) upon adding excess amounts of a tetra-thiol crosslinker. Characterized according to their size, surface charge, morphology, and thiol amounts, these nanoparticles were immobilized on gold surfaces that mimicked gold-coated mass sensor platforms. The PEG-based nanoparticles, prepared especially by PEG6K-diMA polymers, were shown to result in the preparation of a monolayer and smooth coating of 80–120 nm thickness. Cysteine-modified NTS(8–13) peptide (RRPYIL) was conjugated to thiolated NP with reversible disulfide bonds and it was demonstrated that its cleavage with a reducing agent such as dithiothreitol (DTT) restores the NP-immobilized gold surface for at least two cycles. Together with its binding studies to NTSR2 antibodies, it was revealed that the peptide-conjugated NP-modified gold surface could be employed as a model for a reusable sensor surface for the detection of biomarkers of same or different types. Full article

Background/Objectives: Leukocytes play a significant role in both acute kidney injury (AKI) and chronic kidney disease (CKD), contributing to pathogenesis and tissue damage. The process of leukocyte infiltration into the inflamed tissues is mediated by the interactions between the leukocytes and cell adhesion molecules (CAMs, i.e., E-selectin, P-selectin, and VCAM-1) present on the inner surface of the inflamed vasculature. Directly interfering with these interactions is a viable strategy to limit the extent of excessive inflammation; however, several small-molecule drug candidates failed during clinical translation. We hypothesized that a synthetic polymer presenting multiple copies of the high-affinity E-selecting binding peptide (P-Esbp) could block E-selectin-mediated functions and decrease leukocytes infiltration, thus reducing the extent of inflammatory kidney injury. Methods: P-Esbp was synthesized by conjugating E-selecting binding peptide (Esbp) to N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer with reactive ester groups via aminolysis. The effects of P-Esbp treatment on kidney injury were investigated in two different models: AKI model (renal ischemia—reperfusion injury—RIRI) and CKD model (adenine-induced kidney injury). Results: We found that the mRNA levels of E-selectin were up-regulated in the kidney following acute and chronic tissue injury. P-Esbp demonstrated an extended half-life time in the bloodstream, and the polymer accumulated significantly in the liver, lungs, and kidneys within 4 h post injection. Treatment with P-Esbp suppressed the up-regulation of E-selectin in mice with RIRI and attenuated the inflammatory process. In the adenine-induced CKD model, the use of the E-selectin blocking copolymer had little impact on the progression of kidney injury, owing to the compensating function of P-selectin and VCAM-1. Conclusion: Our findings provide valuable insights into the interconnection between CAMs and compensatory mechanisms in controlling leukocyte migration in AKI and CKD. The combination of multiple CAM blockers, given simultaneously, may provide protective effects for preventing excessive leukocyte infiltration and control renal injury. Full article

As a key means to solve energy and environmental problems, photocatalytic technology has made remarkable progress in recent years. Organic semiconductor materials offer structural diversity and tunable energy levels and thus attracted great attention. Among them, porphyrin and its derivatives show great potential in photocatalytic reactions and light therapy due to their unique large-π conjugation structure, high apparent quantum efficiency, tailorable functionality, and excellent biocompatibility. Compared to unassembled porphyrin molecules, supramolecular porphyrin assemblies facilitate the solar light absorption and improve the charge transfer and thus exhibit enhanced photocatalytic performance. Herein, the research progress of porphyrin-based supramolecular assemblies, including the construction, the regulation of charge separation and transfer, stability, and application in photocatalysis, was systematically reviewed. The construction strategy of porphyrin supramolecules, the mechanism of charge separation, and the intrinsic relationship of assembling structure-charge transfer-photocatalytic performance received special attention. Surfactants, peptide molecules, polymers, and metal ions were introduced to improve the stability of the porphyrin assemblies. Donor-acceptor structure and co-catalysts were incorporated to inhibit the recombination of the photoinduced charges. These increase the understanding of the porphyrin supramolecules and provide ideas for the design of high-performance porphyrin-based photocatalysts. Full article

As a promising polymer for the production of biomaterials and drug delivery systems, poly(lactic acid) (PLA) is characterized by its relative hydrophobicity, as well as its chemical and biological inertness. Here, we aimed to improve the biological properties of PLA-based materials via the covalent attachment of a hydrophilic biocompatible glycopolymer, namely poly(2-deoxy-N-methacrylamido-D-glucose) (PMAG) on their surface. PMAG is a water-soluble polymer that contains glucose units in its side chains, which are responsible for good biocompatibility and the ability to attach bioactive molecules. In the developed protocol, PMAG was synthesized by controlled radical polymerization in the presence of a reversible addition–fragmentation chain transfer (RAFT) agent, followed by the conversion of glycopolymer terminal dithiobenzoate functionality into a primary amino group (PMAG-NH₂). PLA-based films served as model aliphatic polyester materials for developing the surface biofunctionalization protocol. According to that, PMAG-NH₂ covalent immobilization was carried out after alkali treatment, allowing the generation of the surface-located carboxyl groups and their activation. The developed modification method provided a one-point attachment of hydrophilic PMAG to the hydrophobic PLA surface. PMAG samples, which differed by the degree of polymerization, and the variation of polymer concentration in the reaction medium were applied to investigate the modification efficacy and grafting density. The developed single-point polymer grafting approach provided the efficient functionalization with a grafting density in the range of 5–23 nmol/cm². The neat and modified polymer films were characterized by a number of methods, namely atomic force microscopy, thermogravimetric analysis, ellipsometry, and contact angle measurements. In addition, an ArgGlyAsp-containing peptide (RGD peptide) was conjugated to the PMAG macromolecules grafted on the surface of PLA films. It was shown that both surface modification with PMAG and with PMAG-RGD peptide enhanced the adhesion and growth of mesenchymal stem cells as compared to a neat PLA surface. Full article

A targeted micellar formation of doxorubicin (Dox) and curcumin (Cur) was evaluated to enhance the efficacy and reduce the toxicity of these drugs in KG1a leukemic stem cells (LSCs) compared to EoL-1 leukemic cells. Dox-Cur-micelle (DCM) was developed to improve the cell uptake of both compounds in LSCs. Cur-micelle (CM) was produced to compare with DCM. DCM and CM were conjugated with two FLT3 (FMS-like tyrosine kinase)-specific peptides (CKR; C and EVQ; E) to increase drug delivery to KG1a via the FLT3 receptor (AML marker). They were formulated using a film-hydration technique together with a pH-induced self-assembly method. The optimal drug-to-polymer weight ratios for the DCM and CM formulations were 1:40. The weight ratio of Dox and Cur in DCM was 1:9. DCM and CM exhibited a particle size of 20–25 nm with neutral charge and a high %EE. Each micelle exhibited colloidal stability and prolonged drug release. Poloxamer 407 (P407) was modified with terminal azides and conjugated to FLT3-targeting peptides with terminal alkynes. DCM and CM coupled with peptides C, E, and C + E exhibited a higher particle size. Moreover, DCM-C + E and CM-C + E showed the highest toxicity in KG-1a and EoL-1 cells. Using two peptides likely improves the probability of micelles binding to the FLT3 receptor and induces cytotoxicity in leukemic stem cells. Full article

Growing resistance to traditional antibiotics poses a global threat to public health. In this regard, modification of known antibiotics, but with limited applications due to side effects, is one of the extremely promising approaches at present. In this study, we proposed the synthesis of novel complex polymeric conjugates of the peptide antibiotic colistin (CT). A biocompatible and water-soluble synthetic glycopolymer, namely, poly(2-deoxy-2-methacrylamido-D-glucose) (PMAG), was used as a polymer carrier. In addition to monoconjugates containing CT linked to PMAG by hydrolyzable and stable bonds, a set of complex conjugates also containing the siderophore deferoxamine (DFOA) and vitamin B12 was developed. The structures of the conjugates were confirmed by ¹H NMR and FTIR-spectroscopy, while the compositions of conjugates were determined by UV–Vis spectrophotometry and HPLC analysis. The buffer media with pH 7.4, corresponding to blood or ileum pH, and 5.2, corresponding to the intestinal pH after ingestion or pH in the focus of inflammation, were used to study the release of CT. The resulting conjugates were examined for cytotoxicity and antimicrobial activity. All conjugates showed less cytotoxicity than free colistin. A Caco-2 cell permeability assay was carried out for complex conjugates to simulate the drug absorption in the intestine. In contrast to free CT, which showed very low permeability through the Caco-2 monolayer, the complex polymeric conjugates of vitamin B12 and CT provided significant transport. The antimicrobial activity of the conjugates depended on the conjugate composition. It was found that conjugates containing CT linked to the polymer by a hydrolyzable bond were found to be more active than conjugates with a non-hydrolyzable bond between CT and PMAG. Conjugates containing DFOA complexed with Fe³⁺ were characterized by enhanced antimicrobial activity against Pseudomonas aeruginosa compared to other conjugates. Full article

Nucleopeptides (NPs) represent synthetic polymers created by attaching nucleobases to the side chains of amino acid residues within peptides. These compounds amalgamate the characteristics of peptides and nucleic acids, showcasing a unique ability to recognize RNA structures. In this study, we present the design and synthesis of Fmoc-protected nucleobase amino acids (1,4-TzlNBAs) and a new class of NPs, where canonical nucleobases are affixed to the side chain of L-homoalanine (Hal) through a 1,4-linked-1,2,3-triazole (HalTzl). Fmoc-protected 1,4-TzlNBAs suitable for HalTzl synthesis were obtained via Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) conjugation of Fmoc-L-azidohomoalanine (Fmoc-Aha) and N1- or N9-propargylated nucleobases or their derivatives. Following this, two trinucleopeptides, HalTzl_AAA and HalTzl_AGA, and the hexanucleopeptide HalTzl_TCCCAG, designed to complement bulge and outer loop structures of TAR (trans-activation response element) RNA HIV-1, were synthesized using the classical solid-phase peptide synthesis (SPPS) protocol. The binding between HalTzls and fluorescently labeled 5′-(FAM(6))-TAR UCU and UUU mutant was characterized using circular dichroism (CD) and fluorescence spectroscopy. CD results confirmed the binding of HalTzls to TAR RNA, which was evident by a decrease in ellipticity band intensity around 265 nm during complexation. CD thermal denaturation studies indicated a relatively modest effect of complexation on the stability of TAR RNA structure. The binding of HalTzls at an equimolar ratio only marginally increased the melting temperature (T_m) of the TAR RNA structure, with an increment of less than 2 °C in most cases. Fluorescence spectroscopy revealed that HalTzl_AAA and HalTzl_AGA, complementary to UUU or UCU bulges, respectively, exhibited disparate affinities for the TAR RNA structure (with K_d ≈ 30 and 256 µM, respectively). Hexamer HalTzl_TCCCAG, binding to the outer loop of TAR_UCU, demonstrated a moderate affinity with K_d ≈ 38 µM. This study demonstrates that newly designed HalTzls effectively bind the TAR RNA structure, presenting a potential new class of RNA binders and may be a promising scaffold for the development of a new class of antiviral drugs. Full article

Mucosal vaccines are highly attractive due to high patient compliance and their suitability for mass immunizations. However, all currently licensed mucosal vaccines are composed of attenuated/inactive whole microbes, which are associated with a variety of safety concerns. In contrast, modern subunit vaccines use minimal pathogenic components (antigens) that are safe but typically poorly immunogenic when delivered via mucosal administration. In this study, we demonstrated the utility of various functional polymer-based nanostructures as vaccine carriers. A Group A Streptococcus (GAS)-derived peptide antigen (PJ8) was selected in light of the recent global spread of invasive GAS infection. The vaccine candidates were prepared by either conjugation or physical mixing of PJ8 with rod-, sphere-, worm-, and tadpole-shaped polymeric nanoparticles. The roles of nanoparticle shape and antigen conjugation in vaccine immunogenicity were demonstrated through the comparison of three distinct immunization pathways (subcutaneous, intranasal, and oral). No additional adjuvant or carrier was required to induce bactericidal immune responses even upon oral vaccine administration. Full article

For successful therapeutic interventions in cancer immunotherapy, strong antigen-specific immune responses are required. To this end, immunostimulating cues must be combined with antigens to simultaneously arrive at antigen-presenting cells and initiate cellular immune responses. Recently, imidazoquinolines have shown their vast potential as small molecular Toll-like receptor 7/8 (TLR7/8) agonists for immunostimulation when delivered by nanocarriers. At the same time, peptide antigens are promising antigen candidates but require combination with immune-stimulating adjuvants to boost their immunogenicity and exploit their full potential. Consequently, we herein present biodegradable polycarbonate nanogels as versatile delivery system for adjuvants within the particles’ core as well as for peptide antigens by surface decoration. For that purpose, orthogonally addressable multifunctional polycarbonate block copolymers were synthesized, enabling adjuvant conjugation through reactive ester chemistry and peptide decoration by strain-promoted alkyne-azide cycloaddition (SPAAC). In preparation for SPAAC, CD4⁺-specific peptide sequences of the model protein antigen ovalbumin were equipped with DBCO-moieties by site-selective modification at their N-terminal cysteine. With their azide groups exposed on their surface, the adjuvant-loaded nanogels were then efficiently decorated with DBCO-functional CD4⁺-peptides by SPAAC. In vitro evaluation of the adjuvant-loaded peptide-decorated gels then confirmed their strong immunostimulating properties as well as their high biocompatibility. Despite their covalent conjugation, the CD4⁺-peptide-decorated nanogels led to maturation of primary antigen-presenting cells and the downstream priming of CD4⁺-T cells. Subsequently, the peptide-decorated nanogels loaded with TLR7/8 agonist were successfully processed by antigen-presenting cells, enabling potent immune responses for future application in antigen-specific cancer immunotherapy. Full article

Polymer–drug conjugates (PDCs) have shown great promise in enhancing the efficacy and safety of cancer therapy. These conjugates combine the advantageous properties of both polymers and drugs, leading to improved pharmacokinetics, controlled drug release, and targeted delivery to tumor tissues. This review provides a comprehensive overview of recent developments in PDCs for cancer therapy. First, various types of polymers used in these conjugates are discussed, including synthetic polymers, such as poly(↋-caprolactone) (PCL), D-α-tocopheryl polyethylene glycol (TPGS), and polyethylene glycol (PEG), as well as natural polymers such as hyaluronic acid (HA). The choice of polymer is crucial to achieving desired properties, such as stability, biocompatibility, and controlled drug release. Subsequently, the strategies for conjugating drugs to polymers are explored, including covalent bonding, which enables a stable linkage between the polymer and the drug, ensuring controlled release and minimizing premature drug release. The use of polymers can extend the circulation time of the drug, facilitating enhanced accumulation within tumor tissues through the enhanced permeability and retention (EPR) effect. This, in turn, results in improved drug efficacy and reduced systemic toxicity. Moreover, the importance of tumor-targeting ligands in PDCs is highlighted. Various ligands, such as antibodies, peptides, aptamers, folic acid, herceptin, and HA, can be incorporated into conjugates to selectively deliver the drug to tumor cells, reducing off-target effects and improving therapeutic outcomes. In conclusion, PDCs have emerged as a versatile and effective approach to cancer therapy. Their ability to combine the advantages of polymers and drugs offers enhanced drug delivery, controlled release, and targeted treatment, thereby improving the overall efficacy and safety of cancer therapies. Further research and development in this field has great potential to advance personalized cancer treatment options. Full article

To monitor the release of fluorinated drugs from polymeric carriers, a novel ¹⁹F MRI enzyme-responsive contrast agent was developed and tested. This contrast agent was prepared by conjugation of 5-fluorouracil (5-FU) to hyperbranched poly(N,N-dimethylacrylamide) (HB-PDMA) via an enzyme-degradable peptide linker. Due to the different molecular sizes, the release of 5-FU from the 5-FU polymer conjugate resulted in a sufficiently substantial difference in spin-spin T₂ ¹⁹F NMR/MRI relaxation time that enabled differentiating between attached and released drug states. The 5-FU polymer conjugate exhibited a broad signal and short T₂ relaxation time under ¹⁹F NMR analysis. Incubation with the enzyme induced the release of 5-FU, accompanied by an extension of T₂ relaxation times and an enhancement in the ¹⁹F MRI signal. This approach is promising for application in the convenient monitoring of 5-FU drug release and can be used to monitor the release of other fluorinated drugs. Full article

The growing evolution of bacterial resistance to antibiotics represents a global issue that not only impacts healthcare systems but also political and economic processes. This necessitates the development of novel antibacterial agents. Antimicrobial peptides have shown promise in this regard. Thus, in this study, a new functional polymer was synthesized by joining a short oligopeptide sequence (Phe-Lys-Phe-Leu, FKFL) to the surface of a second-generation polyamidoamine (G2 PAMAM) dendrimer as an antibacterial component. This method of synthesis proved simple and resulted in a high conjugation yield of the product FKFL-G2. To determine its antibacterial potential, FKFL-G2 was subsequently analyzed via mass spectrometry, a cytotoxicity assay, bacterial growth assay, colony-forming unit assay, membrane permeabilization assay, transmission electron microscopy, and biofilm formation assay. FKFL-G2 was found to exhibit low toxicity to noncancerous NIH3T3 cells. Additionally, FKFL-G2 had an antibacterial effect on Escherichia coli and Staphylococcus aureus strains by interacting with and disrupting the bacterial cell membrane. Based on these findings, FKFL-G2 shows promise as a potential antibacterial agent. Full article

Over the past few decades, the complexity of molecular entities being advanced for therapeutic purposes has continued to evolve. A main propellent fueling innovation is the perpetual mandate within the pharmaceutical industry to meet the needs of novel disease areas and/or delivery challenges. As new mechanisms of action are uncovered, and as our understanding of existing mechanisms grows, the properties that are required and/or leveraged to enable therapeutic development continue to expand. One rapidly evolving area of interest is that of chemically enhanced peptide and protein therapeutics. While a variety of conjugate molecules such as antibody–drug conjugates, peptide/protein–PEG conjugates, and protein conjugate vaccines are already well established, others, such as antibody–oligonucleotide conjugates and peptide/protein conjugates using non-PEG polymers, are newer to clinical development. This review will evaluate the current development landscape of protein-based chemical conjugates with special attention to considerations such as modulation of pharmacokinetics, safety/tolerability, and entry into difficult to access targets, as well as bioavailability. Furthermore, for the purpose of this review, the types of molecules discussed are divided into two categories: (1) therapeutics that are enhanced by protein or peptide bioconjugation, and (2) protein and peptide therapeutics that require chemical modifications. Overall, the breadth of novel peptide- or protein-based therapeutics moving through the pipeline each year supports a path forward for the pursuit of even more complex therapeutic strategies. Full article