Antimicrobial peptide-grafted PLGA-PEG nanoparticles to fight bacterial wound infections

Anti-Candida Activity of Cysteine-Modified Amidated Decoralin in the Presence of Engineered Nanomaterials

Background: Candidiasis remains a chief concern in global healthcare. Drug safety issues and increasing resistance make it urgent to develop alternative antifungal agents, namely antimicrobial peptides. Amidated decoralin (Dec-CONH2) possesses considerable anti-Candida activity, and its association with nanocarriers could help in enhancing efficacy while reducing intrinsic toxicity to the host. Methods: We studied an N-terminal cysteine-modified version of the peptide (Cys-Dec-CONH2) and screened the effects of different nanosystems (polymeric nanoparticles (NPs), liposomes and gold NPs) on its activity against azole-sensitive and azole-resistant Candida species using a clinically relevant in vitro assay. Results: The antifungal activity of Cys-Dec-CONH2 was maintained (minimum inhibitory concentration (MIC) = 16-64 µg/mL), but the presence of poly(d,l-lactic-co-glycolic acid) (PLGA)- and polycaprolactone-based NPs impaired the antifungal effect of the peptide (MIC > 256 µg/mL). This effect was milder for polystyrene-based NPs, liposomes, and gold NPs (MIC ≤ 128 µg/mL). Additionally, the covalent surface functionalization of PLGA-based NPs with Cys-Dec-CONH2 or the presence of relevant biomolecules (albumin and mucin) resulted in complete inhibition of antifungal activity. Conclusions: Our data suggest that Cys-Dec-CONH2 is able to establish strong interfacial interactions with different nanomaterials, which need to be considered when developing nanomedicines based on this peptide for the management of candidiasis.

Antimicrobial peptide biological activity, delivery systems and clinical translation status and challenges

Antibiotic resistance is currently one of the most significant threats to global public health and safety. And studies have found that over the next 25 years, 39 million people will die directly and 169 million indirectly due to antibiotic-resistant diseases. Consequently, the development of new types of antimicrobial drugs is urgently needed. Antimicrobial peptides (AMPs) constitute an essential component of the innate immune response in all organisms. They exhibit a distinctive mechanism of action that endows them with a broad spectrum of biological activities, including antimicrobial, antibiofilm, antiviral, and anti-inflammatory effects. However, AMPs also present certain limitations, such as cytotoxicity, susceptibility to protein hydrolysis, and poor pharmacokinetic properties, which have impeded their clinical application. The development of delivery systems can address these challenges by modifying AMP delivery and enabling precise, controlled release at the site of infection or disease. This review offers a comprehensive analysis of the mechanisms of action and biological advantages of AMPs. and systematically evaluate how emerging drug delivery systems, such as nanoparticles and hydrogels, enhance the stability and bioavailability of AMPs, discussing both their strengths and limitations. Moreover, unlike previous reviews, this review highlight the most recent clinically approved AMP-based drugs and those currently in development, emphasizing the key challenges in translating these drugs into clinical practice. With these perspectives, it is hoped that this review will provide some insights into overcoming translational barriers and advancing AMPs drugs into clinical practice.

Advances in Artificially Designed Antibacterial Active Antimicrobial Peptides

Antibacterial resistance has emerged as a significant global concern, necessitating the urgent development of new antibacterial drugs. Antimicrobial peptides (AMPs) are naturally occurring peptides found in various organisms. Coupled with a wide range of antibacterial activity, AMPs are less likely to develop drug resistance and can act as potential agents for treating bacterial infections. However, their characteristics, such as low activity, instability, and toxicity, hinder their clinical application. Consequently, researchers are inclined towards artificial design and optimization based on natural AMPs. This review discusses the research advancements in the field of artificial designing and optimization of various AMPs. Moreover, it highlights various strategies for designing such peptides, aiming to provide valuable insights for developing novel AMPs.

Advanced Polymeric Nanoparticles for Cancer Immunotherapy: Materials Engineering, Immunotherapeutic Mechanism and Clinical Translation

Cancer immunotherapy, which leverages immune system components to treat malignancies, has emerged as a cornerstone of contemporary therapeutic strategies. Yet, critical concerns about the efficacy and safety of cancer immunotherapies remain formidable. Nanotechnology, especially polymeric nanoparticles (PNPs), offers unparalleled flexibility in manipulation-from the chemical composition and physical properties to the precision control of nanoassemblies. PNPs provide an optimal platform to amplify the potency and minimize systematic toxicity in a broad spectrum of immunotherapeutic modalities. In this comprehensive review, the basics of polymer chemistry, and state-of-the-art designs of PNPs from a physicochemical standpoint for cancer immunotherapy, encompassing therapeutic cancer vaccines, in situ vaccination, adoptive T-cell therapies, tumor-infiltrating immune cell-targeted therapies, therapeutic antibodies, and cytokine therapies are delineated. Each immunotherapy necessitates distinctively tailored design strategies in polymeric nanoplatforms. The extensive applications of PNPs, and investigation of their mechanisms of action for enhanced efficacy are particularly focused on. The safety profiles of PNPs and clinical research progress are discussed. Additionally, forthcoming developments and emergent trends of polymeric nano-immunotherapeutics poised to transform cancer treatment paradigms into clinics are explored.

Recent Advances in Peptide-Loaded PLGA Nanocarriers for Drug Delivery and Regenerative Medicine

Peptide-loaded poly(lactide-co-glycolide) (PLGA) nanocarriers represent a transformative approach to addressing the challenges of peptide-based therapies. These systems offer solutions to peptide instability, enzymatic degradation, and limited bioavailability by providing controlled release, targeted delivery, and improved stability. The versatility of PLGA nanocarriers extends across therapeutic domains, including cancer therapy, neurodegenerative diseases, vaccine development, and regenerative medicine. Innovations in polymer chemistry, surface functionalization, and advanced manufacturing techniques, such as microfluidics and electrospraying, have further enhanced the efficacy and scalability of these systems. This review highlights the key physicochemical properties, preparation strategies, and proven benefits of peptide-loaded PLGA systems, emphasizing their role in sustained drug release, immune activation, and tissue regeneration. Despite remarkable progress, challenges such as production scalability, cost, and regulatory hurdles remain.

PEG-Polymeric Nanocarriers Alleviate the Immunosuppressive Effects of Free 4-Thiazolidinone-Based Chemotherapeutics on T Lymphocyte Function and Cytokine Production

Purpose

Our study aimed to assess the effects of anticancer 4-thiazolidinone-based free water-insoluble therapeutics Les-3288 and Les-3833 and their waterborne complexes with branched PEG-containing polymeric carriers (A24-PEG550 and A24-PEG750) on immune response.

Methods

Human peripheral blood was used to study in vitro lymphocyte proliferative function, leukocyte phagocytic activity and respiratory burst, and cytokine production.

Results

The binding of the polymer to the anticancer drug Les-3288, which is intended to mitigate the immunosuppressive effects of the free drug on the proliferative activity of T lymphocytes and T-dependent B cells, demonstrated comparable efficacy for both A24-PEG750 and A24-PEG550 nanocarriers. Furthermore, it was observed that the drug-polymer complex significantly increased the reduced levels of IFN-γ and TNF-α resulting from free Les-3288. Conversely, the reduced levels of IL-6 and IL-4 remained unchanged. Administration of either form of Les-3288 had no effect on the phagocytic activity of monocytes, granulocytes or the respiratory burst of granulocytes. Due to the reduced cell viability and increased cytotoxicity associated with Les-3833, tenfold lower doses were selected for the immune assays. The effects of free Les-3833 on lymphocyte proliferative function resulted in significant stimulation of T-dependent B cells. The binding of Les-3833 to the smaller carrier, A24-PEG550 was found to maintain the stimulatory effect on B lymphocytes. While no effect of free Les-3833 on the granulocyte phagocytic activity was observed, binding of Les-3833 to both polymeric carriers resulted in a decrease in granulocyte phagocytic activity and respiratory burst, with no observable effect on monocytes. Monitoring of cytokine production showed no significant effect of either form of Les-3833 on the production of IFN-γ and IL-6. In the context of TNF-α and IL-4, the positive effect of polymer binding on restoring suppressed cytokine levels induced by the Les-3833 free drug was slightly more favorable for A24-PEG750.

Conclusion

The drug complexation with novel PEGylated carriers is a promising way for efficient therapeutic development.

Dhvar5-chitosan nanogels and their potential to improve antibiotics activity

Infection is one of the main causes of orthopedic implants failure, with antibiotic-resistant bacteria playing a crucial role in this outcome. In this work, antimicrobial nanogels were developed to be applied in situ as implant coating to prevent orthopedic-device-related infections. To that regard, a broad-spectrum antimicrobial peptide, Dhvar5, was grafted onto chitosan via thiol-norbornene "photoclick" chemistry. Dhvar5-chitosan nanogels (Dhvar5-NG) were then produced using a microfluidic system. Dhvar5-NG (1010 nanogels (NG)/mL) with a Dhvar5 concentration of 6 μg/mL reduced the burden of the most critical bacteria in orthopedic infections - methicillin-resistant Staphylococcus aureus (MRSA) - after 24 h in medium supplemented with human plasma proteins. Transmission electron microscopy showed that Dhvar5-NG killed bacteria by membrane disruption and cytoplasm release. No signs of cytotoxicity against a pre-osteoblast cell line were verified upon incubation with Dhvar5-NG. To further explore therapeutic alternatives, the potential synergistic effect of Dhvar5-NG with antibiotics was evaluated against MRSA. Dhvar5-NG at a sub-minimal inhibitory concentration (109 NG/mL) demonstrated synergistic effect with oxacillin (4-fold reduction: from 2 to 0.5 μg/mL) and piperacillin (2-fold reduction: from 2 to 1 μg/mL). This work supports the use of Dhvar5-NG as adjuvant of antibiotics to the prevention of orthopedic devices-related infections.

How can biomaterial-conjugated antimicrobial peptides fight bacteria and be protected from degradation?

The emergence of antibiotic-resistant bacteria is a serious threat to public health. Antimicrobial peptides (AMP) are a powerful alternative to antibiotics due to their low propensity to induce bacterial resistance. However, cytotoxicity and short half-lives have limited their clinical translation. To overcome these problems, AMP conjugation has gained relevance in the biomaterials field. Nevertheless, few studies describe the influence of conjugation on enzymatic protection, mechanism of action and antimicrobial efficacy. This review addresses this gap by providing a detailed comparison between conjugated and soluble AMP. Additionally, commonly employed chemical reactions and factors to consider when promoting AMP conjugation are reviewed. The overall results suggested that AMP conjugated onto biomaterials are specifically protected from degradation by trypsin and/or pepsin. However, sometimes, their antimicrobial efficacy was reduced. Due to limited conformational freedom in conjugated AMP, compared to their soluble forms, they appear to act initially by creating small protuberances on bacterial membranes that may lead to the alteration of membrane potential and/or formation of holes, triggering cell death. Overall, AMP conjugation onto biomaterials is a promising strategy to fight infection, particularly associated to the use of medical devices. Nonetheless, some details need to be addressed before conjugated AMP reach clinical practice. STATEMENT OF SIGNIFICANCE: Covalent conjugation of antimicrobial peptides (AMP) has been one of the most widely used strategies by bioengineers, in an attempt to not only protect AMP from proteolytic degradation, but also to prolong their residence time at the target tissue. However, an explanation for the mode of action of conjugated AMP is still lacking. This review extensively gathers works on AMP conjugation and puts forward a mechanism of action for AMP when conjugated onto biomaterials. The implications of AMP conjugation on antimicrobial activity, cytotoxicity and resistance to proteases are all discussed. A thorough review of commonly employed chemical reactions for this conjugation is also provided. Finally, details that need to be addressed for conjugated AMP to reach clinical practice are discussed.

One-Pot Microfluidics to Engineer Chitosan Nanoparticles Conjugated with Antimicrobial Peptides Using "Photoclick" Chemistry: Validation Using the Gastric Bacterium Helicobacter pylori

Surface bioconjugation of antimicrobial peptides (AMP) onto nanoparticles (AMP-NP) is a complex, multistep, and time-consuming task. Herein, a microfluidic system for the one-pot production of AMP-NP was developed. Norbornene-modified chitosan was used for NP production (NorChit-NP), and thiolated-AMP was grafted on their surface via thiol-norbornene "photoclick" chemistry over exposure of two parallel UV LEDs. The MSI-78A was the AMP selected due to its high activity against a high priority (level 2) antibiotic-resistant gastric pathogen: Helicobacter pylori (H. pylori). AMP-NP (113 ± 43 nm; zeta potential 14.3 ± 7 mV) were stable in gastric settings without a cross-linker (up to 5 days in pH 1.2) and bactericidal against two highly pathogenic H. pylori strains (1011 NP/mL with 96 μg/mL MSI-78A). Eradication was faster for H. pylori 26695 (30 min) than for H. pylori J99 (24 h), which was explained by the lower minimum bactericidal concentration of soluble MSI-78A for H. pylori 26695 (32 μg/mL) than for H. pylori J99 (128 μg/mL). AMP-NP was bactericidal by inducing H. pylori cell membrane alterations, intracellular reorganization, generation of extracellular vesicles, and leakage of cytoplasmic contents (transmission electron microscopy). Moreover, NP were not cytotoxic against two gastric cell lines (AGS and MKN74, ATCC) at bactericidal concentrations. Overall, the designed microfluidic setup is a greener, simpler, and faster approach than the conventional methods to obtain AMP-NP. This technology can be further explored for the bioconjugation of other thiolated-compounds.

Immune cell receptor-specific nanoparticles as a potent adjuvant for nasal split influenza vaccine delivery

Mucosal delivery systems have gained much attention as effective way for antigen delivery that induces both systemic and mucosal immunity. However, mucosal vaccination faces the challenges of mucus barrier and effective antigen uptake and presentation. In particular, split, subunit and recombinant protein vaccines that do not have an intact pathogen structure lack the efficiency to stimulate mucosal immunity. In this study, poly (lactic acid-co-glycolic acid-polyethylene glycol) (PLGA-PEG) block copolymers were modified by mannose to form a PLGA-PEG-Man conjugate (mannose modified PLGA-PEG), which were characterized. The novel nanoparticles (NPs) prepared with this material had a particle size of about 150 nm and a zeta potential of -15 mV, and possessed ideal mucus permeability, immune cell targeting, stability and low toxicity. Finally, PLGA-PEG-Man nanoparticles (PLGA-PEG-Man NPs) were successfully applied for intranasal delivery of split influenza vaccine in rat for the first time, which triggered strong systemic and mucosal immune responses. These studies suggest that PLGA-PEG-Man NPs could function as competitive potential nano-adjuvants to address the challenge of inefficient mucosal delivery of non-allopathogenic antigens.

Synthesis of L-Ornithine- and L-Glutamine-Linked PLGAs as Biodegradable Polymers

L-ornithine and L-glutamine are amino acids used for ammonia and nitrogen transport in the human body. Novel biodegradable synthetic poly(lactic-co-glycolic acid) derivatives were synthesized via conjugation with L-ornithine or L-glutamine, which were selected due to their biological importance. L-ornithine or L-glutamine was integrated into a PLGA polymer with EDC coupling reactions as a structure developer after the synthesis of PLGA via the polycondensation and ring-opening polymerization of lactide and glycolide. The chemical, thermal, and degradation property-structure relationships of PLGA, PLGA-L-ornithine, and PLGA-L-glutamine were identified. The conjugation between PLGA and the amino acid was confirmed through observation of an increase in the number of carbonyl carbons in the range of 170-160 ppm in the 13C NMR spectrum and the signal of the amide carbonyl vibration at about 1698 cm-1 in the FTIR spectrum. The developed PLGA-L-ornithine and PLGA-L-glutamine derivatives were thermally stable and energetic materials. In addition, PLGA-L-ornithine and PLGA-L-glutamine, with their unique hydrophilic properties, had faster degradation times than PLGA in terms of surface-type erosion, which covers their requirements. L-ornithine- and L-glutamine-linked PLGAs are potential candidates for development into biodegradable PLGA-derived biopolymers that can be used as raw materials for biomaterials.