Glycosylated Nanoparticles as Efficient Antimicrobial Delivery Agents

Recent Advances in Polymers Bearing Activated Esters for the Synthesis of Glycopolymers by Postpolymerization Modification

Glycopolymers are functional polymers with saccharide moieties on their side chains and are attractive candidates for biomaterials. Postpolymerization modification can be employed for the synthesis of glycopolymers. Activated esters are useful in various fields, including polymer chemistry and biochemistry, because of their high reactivity and ease of reaction. In particular, the formation of amide bonds caused by the reaction of activated esters with amino groups is of high synthetic chemical value owing to its high selectivity. It has been employed in the synthesis of various functional polymers, including glycopolymers. This paper reviews the recent advances in polymers bearing activated esters for the synthesis of glycopolymers by postpolymerization modification. The development of polymers bearing hydrophobic and hydrophilic activated esters is described. Although water-soluble activated esters are generally unstable and hydrolyzed in water, novel polymer backbones bearing water-soluble activated esters are stable and useful for postpolymerization modification for synthesizing glycopolymers in water. Dual postpolymerization modification can be employed to modify polymer side chains using two different molecules. Thiolactone and glycine propargyl esters on the polymer backbone are described as activated esters for dual postpolymerization modification.

Physical and Functional Characterization of PLGA Nanoparticles Containing the Antimicrobial Peptide SAAP-148

Synthetic antimicrobial and antibiofilm peptide (SAAP-148) commits significant antimicrobial activities against antimicrobial resistant (AMR) planktonic bacteria and biofilms. However, SAAP-148 is limited by its low selectivity index, i.e., ratio between cytotoxicity and antimicrobial activity, as well as its bioavailability at infection sites. We hypothesized that formulation of SAAP-148 in PLGA nanoparticles (SAAP-148 NPs) improves the selectivity index due to the sustained local release of the peptide. The aim of this study was to investigate the physical and functional characteristics of SAAP-148 NPs and to compare the selectivity index of the formulated peptide with that of the peptide in solution. SAAP-148 NPs displayed favorable physiochemical properties [size = 94.1 ± 23 nm, polydispersity index (PDI) = 0.08 ± 0.1, surface charge = 1.65 ± 0.1 mV, and encapsulation efficiency (EE) = 86.7 ± 0.3%] and sustained release of peptide for up to 21 days in PBS at 37 °C. The antibacterial and cytotoxicity studies showed that the selectivity index for SAAP-148 NPs was drastically increased, by 10-fold, regarding AMR Staphylococcus aureus and 20-fold regarding AMR Acinetobacter baumannii after 4 h. Interestingly, the antibiofilm activity of SAAP-148 NPs against AMR S. aureus and A. baumannii gradually increased overtime, suggesting a dose-effect relationship based on the peptide's in vitro release profile. Using 3D human skin equivalents (HSEs), dual drug SAAP-148 NPs and the novel antibiotic halicin NPs provided a stronger antibacterial response against planktonic and cell-associated bacteria than SAAP-148 NPs but not halicin NPs after 24 h. Confocal laser scanning microscopy revealed the presence of SAAP-148 NPs on the top layers of the skin models in close proximity to AMR S. aureus at 24 h. Overall, SAAP-148 NPs present a promising yet challenging approach for further development as treatment against bacterial infections.

Mannosylated Gold Nanoclusters Incorporated with a Repurposed Antihistamine Drug Promethazine for Antibacterial and Antibiofilm Applications

Drug repurposing presents a workable strategy in tackling antibiotic resistance. Many known drugs have been repurposed for their applications against different targets. Antihistamines that are usually used to treat allergy symptoms can be combined with nanoscale materials to enhance their efficiency. Herein, we explored the antimicrobial properties of a common antihistamine drug, promethazine, in Gram-positive and Gram-negative bacteria. Being positively charged, promethazine was easily incorporated into the mannose-conjugated bovine serum albumin-stabilized promethazine hydrochloride gold nanoclusters. Capping with d-mannose helped in targeting the bacteria by inhibiting their adhesive appendage called pili. Following their uptake, drugs released inside the bacteria caused reactive oxygen species production and membrane permeability alteration, ultimately resulting in bacterial inhibition. Additionally, they were also explored for biofilm eradication. As observed through staining assays, the number of dead cells increased with increasing concentration of drug-loaded gold nanoclusters in the biofilm mass. Therefore, the as-synthesized mannosylated gold nanoclusters incorporated with promethazine were analyzed for potential antibacterial and antibiofilm applications.

Mucosomes: Intrinsically Mucoadhesive Glycosylated Mucin Nanoparticles as Multi-Drug Delivery Platform

Mucus is a complex barrier for pharmacological treatments and overcoming it is one of the major challenges faced during transmucosal drug delivery. To tackle this issue, a novel class of glycosylated nanoparticles, named "mucosomes," which are based on the most important protein constituting mucus, the mucin, is introduced. Mucosomes are designed to improve drug absorption and residence time on the mucosal tissues. Mucosomes are produced (150-300 nm), functionalized with glycans, and loaded with the desired drug in a single one-pot synthetic process and, with this method, a wide range of small and macro molecules can be loaded with different physicochemical properties. Various in vitro models are used to test the mucoadhesive properties of mucosomes. The presence of functional glycans is indicated by the interaction with lectins. Mucosomes are proven to be storable at 4 °C after lyophilization, and administration through a nasal spray does not modify the morphology of the mucosomes. In vitro and in vivo tests indicate mucosomes do not induce adverse effects under the investigated conditions. This study proposes mucosomes as a ground-breaking nanosystem that can be applied in several pathological contexts, especially in mucus-related disorders.

Susceptibility Pattern of Caspofungin-Coated Gold Nanoparticles Against Clinically Important Candida Species

Purpose: The present study was performed to examine whether caspofungin-coated gold nanoparticles (CAS-AuNPs) may offer the right platform for sensitivity induction in resistant isolates.

Methods: A total of 58 archived Candida species were enrolled in the research. The identification of Candida spp. was performed using polymerase chain reaction-restriction fragment length polymorphism and HWP1 gene amplification approaches. The conjugated CAS-AuNPs were synthesized and then characterized using transmission electron microscopy (TEM) and Zetasizer system to determine their morphology, size, and charge. Furthermore, the efficacy was assessed based on the Clinical and Laboratory Standards Institute M60. Finally, the interaction of CAS-AuNPs with Candida element was evaluated via scanning electron microscopy (SEM).

Results: According to the TEM results, the synthesized CAS-AuNPs had a spherical shape with an average size of 20 nm. The Zeta potential of CAS-AuNPs was -38.2 mV. Statistical analyses showed that CAS-AuNPs could significantly reduce the minimum inhibitory concentration against C. albicans (P =0.0005) and non-albicans Candida (NAC) species (P < 0.0001). All isolates had a MIC value of ≥ 4 µg/ml for CAS, except for C. glabrata. The results of SEM analysis confirmed the effects of AuNPs on the cell wall structure of C. globrata with the formation of pores.

Conclusion: According to findings, CAS-AuNPs conjugates had significant antifungal effects against Candida spp. Therefore, it can be concluded that the encapsulation of antifungal drugs in combination with NPs not only diminishes side effects but also enhances the effectiveness of the medications.

Epithelium-Penetrable Nanoplatform with Enhanced Antibiotic Internalization for Management of Bacterial Keratitis

A standardized regimen for addressing the adverse effects of bacterial keratitis on vision remains an intractable challenge due to poor epithelial penetration and a short corneal retention time. In this study, a new strategy is proposed to implement the direct transport of antibiotics to bacteria-infected corneas via topical administration of an epithelium-penetrable biodriven nanoplatform, thereby enabling the efficacious treatment of bacterial keratitis. The nanoplatforms were composed of amphiphilic glycopolymers containing boron dipyrromethene and boronic acid moieties with stable fluorescence characteristics and the ability to potentiate epithelial penetration deep into the cornea. The boronic acid-derived nanoplatforms enabled efficient cellular internalization through the high affinity of boric acid groups for the diol-containing bacterial cell wall, resulting in enhanced drug penetration and retention inside the pathogenic bacteria. The bacterial cells formed agglomerations after incorporating the nanoplatforms along with a special mechanism to release the encapsulated cargo in response to in situ bacteria. Compared with the drug alone, this smart system achieved enhanced bacterial mortality and attenuated inflammation associated with Staphylococcus aureus-induced keratitis in rats, demonstrating a paradigm for targeted ocular drug delivery and an alternative strategy for managing bacterial keratitis or other bacterial infections by heightening corneal permeability and transcorneal bioavailability.

Glycomacromolecules: Addressing challenges in drug delivery and therapeutic development

Carbohydrate-based materials offer exciting opportunities for drug delivery. They present readily available, biocompatible components for the construction of macromolecular systems which can be loaded with cargo, and can enable targeting of a payload to particular cell types through carbohydrate recognition events established in biological systems. These systems can additionally be engineered to respond to environmental stimuli, enabling triggered release of payload, to encompass multiple modes of therapeutic action, or to simultaneously fulfil a secondary function such as enabling imaging of target tissue. Here, we will explore the use of glycomacromolecules to deliver therapeutic benefits to address key health challenges, and suggest future directions for development of next-generation systems.

Multi-Arm Star-Shaped Glycopolymers with Precisely Controlled Core Size and Arm Length

Star-shaped glycopolymers provide very high binding activities toward lectins. However, a straightforward synthesis method for the preparation of multi-arm glycopolymers in a one-pot approach has been challenging. Herein, we report a rapid synthesis of well-defined multi-arm glycopolymers via Cu(0)-mediated reversible deactivation radical polymerization in aqueous media. d-Mannose acrylamide has been homo- and copolymerized with NIPAM to provide linear arms and then core cross-linked with a bisacrylamide monomer. Thus, the arm length and core size of multi-arm glycopolymers were tuned. Moreover, the stability of multi-arm glycopolymers was investigated, and degradation reactions under acidic or basic conditions were observed. The binding activities of the obtained multi-arm glycopolymers with mannose-specific human lectins, DC-SIGN and MBL, were investigated via surface plasmon resonance spectroscopy. Finally, the encapsulation ability of multi-arm glycopolymers was examined using DHA and Saquinavir below and above the lower critical solution temperature (LCST) of P(NIPAM).

Nano-Based Drug Delivery or Targeting to Eradicate Bacteria for Infection Mitigation: A Review of Recent Advances

Pathogenic bacteria infection is a major public health problem due to the high morbidity and mortality rates, as well as the increased expenditure on patient management. Although there are several options for antimicrobial therapy, their efficacy is limited because of the occurrence of drug-resistant bacteria. Many conventional antibiotics have failed to show significant amelioration in overall survival of infectious patients. Nanomedicine for delivering antibiotics provides an opportunity to improve the efficiency of the antibacterial regimen. Nanosystems used for antibiotic delivery and targeting to infection sites render some benefits over conventional formulations, including increased solubility, enhanced stability, improved epithelium permeability and bioavailability, prolonged antibiotic half-life, tissue targeting, and minimal adverse effects. The nanocarriers' sophisticated material engineering tailors the controllable physicochemical properties of the nanoparticles for bacterial targeting through passive or active targeting. In this review, we highlight the recent progress on the development of antibacterial nanoparticles loaded with antibiotics. We systematically introduce the concepts and amelioration mechanisms of the nanomedical techniques for bacterial eradication. Passive targeting by modulating the nanoparticle structure and the physicochemical properties is an option for efficient drug delivery to the bacteria. In addition, active targeting, such as magnetic hyperthermia induced by iron oxide nanoparticles, is another efficient way to deliver the drugs to the targeted site. The nanoparticles are also designed to respond to the change in environment pH or enzymes to trigger the release of the antibiotics. This article offers an overview of the benefits of antibacterial nanosystems for treating infectious diseases.

Antibiofilm Platform based on the Combination of Antimicrobial Polymers and Essential Oils

The development of potent strategies to counter microbial biofilm is an urgent priority in healthcare. The majority of bacterial infections in humans are biofilm related, however, effective treatments are still lacking especially for combating multidrug-resistant (MDR) strains. Herein, we report an effective antibiofilm platform based on the use of synthetic antimicrobial polymers in combination with essential oils, where the antimicrobial polymers play a secondary role as delivery vehicle for essential oils. Two ternary antimicrobial polymers consisting of cationic primary amines, low-fouling oligo(ethylene glycol) and hydrophobic ethylhexyl groups were synthesized in the form of random and block copolymers, and mixed with either carvacrol or eugenol. Coadministration of these compounds improved the efficacy against Pseudomonas aeruginosa biofilms compared to the individual compounds. We observed about a 60-75% and 70-85% biofilm inhibition effect for all tested combinations against wild-type P. aeruginosa PAO1 and MDR strain PA37, respectively, upon 6.5 h of incubation time. While both random and block copolymers demonstrated similar biofilm inhibition potencies in combination with essential oils, only the block copolymer acted synergistically with essential oils in killing biofilm. Treatment of PAO1 biofilm for 20 min with the block copolymer-oil combinations resulted in the killing of >99.99% of biofilm bacteria. This synergistic bactericidal activity is attributed to the targeted delivery of essential oils to the biofilm, driven by the electrostatic interaction between positively charged delivery vehicles, in the form of polymeric micelles, and negatively charged bacteria. This study thus highlights the advantage of combining essential oils and antimicrobial polymers as an effective avenue for antibacterial applications.

Polydimethylsiloxane-Based Giant Glycosylated Polymersomes with Tunable Bacterial Affinity

A synthetic cell mimic in the form of giant glycosylated polymersomes (GGPs) comprised of a novel amphiphilic diblock copolymer is reported. A synthetic approach involving a poly(dimethylsiloxane) (PDMS) macro-chain transfer agent (macroCTA) and postpolymerization modification was used to marry the hydrophobic and highly flexible properties of PDMS with the biological activity of glycopolymers. 2-Bromoethyl acrylate (BEA) was first polymerized using a PDMS macroCTA ( M_n,th ≈ 4900 g·mol^-1, Đ = 1.1) to prepare well-defined PDMS- b-pBEA diblock copolymers ( Đ = 1.1) that were then substituted with 1-thio-β-d-glucose or 1-thio-β-d-galactose under facile conditions to yield PDMS- b-glycopolymers. Compositions possessing ≈25% of the glycopolymer block (by mass) were able to adopt a vesicular morphology in aqueous solution (≈210 nm in diameter), as indicated by TEM and light scattering techniques. The resulting carbohydrate-decorated polymersomes exhibited selective binding with the lectin concanavalin A (Con A), as demonstrated by turbidimetric experiments. Self-assembly of the same diblock copolymer compositions using an electroformation method yielded GGPs (ranging from 2-20 μm in diameter). Interaction of these cell-sized polymersomes with fimH positive E. coli was then studied via confocal microscopy. The glucose-decorated GGPs were found to cluster upon addition of the bacteria, while galactose-decorated GGPs could successfully interact with (and possibly immobilize) the bacteria without the onset of clustering. This demonstrates an opportunity to modulate the response of these synthetic cell mimics (protocells) toward biological entities through exploitation of selective ligand-receptor interactions, which may be readily tuned through a considered choice of carbohydrate functionality.

Cationic Silver Nanoclusters as Potent Antimicrobials against Multidrug-Resistant Bacteria

Bacterial multidrug resistance (MDR) is a serious healthcare issue caused by the long-term subtherapeutic clinical treatment of infectious diseases. Nanoscale engineering of metal nanoparticles has great potential to address this issue by tuning the nano-bio interface to target bacteria. Herein, we report the use of branched polyethylenimine-functionalized silver nanoclusters (bPEI-Ag NCs) to selectively kill MDR pathogenic bacteria by combining the antimicrobial activity of silver with the selective toxicity of bPEI toward bacteria. The minimum inhibitory concentration of bPEI-Ag NCs was determined against 12 uropathogenic MDR strains and found to be 10- to 15-fold lower than that of PEI and 2- to 3-fold lower than that of AgNO₃ alone. Cell viability and hemolysis assays demonstrated the biocompatibility of bPEI-Ag NCs with human fibroblasts and red blood cells, with selective toxicity against MDR bacteria.

Synthesis of Sub-100 nm Glycosylated Nanoparticles via a One Step, Free Radical, and Surfactant Free Emulsion Polymerization

The facile synthesis of sub-100 nm glyco nanoparticles is presented via a one-step, free radical, and surfactant free emulsion polymerization. It is shown that by using sterically large, hydrophilic glycomonomers such as a lactose acrylamide with the charged azo initiator 4,4'-azobis(4-cyanovaleric acid), growing particles are stabilized enough to reproducibly produce well defined (PDi ≤ 0.1) glycoparticles with diameters below 100 nm.

Chitosan/Cyclodextrin/TPP Nanoparticles Loaded with Quercetin as Novel Bacterial Quorum Sensing Inhibitors

The widespread emergence of antibiotic-resistant bacteria has highlighted the urgent need of alternative therapeutic approaches for human and animal health. Targeting virulence factors that are controlled by bacterial quorum sensing (QS), seems a promising approach. The aims of this study were to generate novel nanoparticles (NPs) composed of chitosan (CS), sulfo-butyl-ether-β-cyclodextrin (Captisol®) and/or pentasodium tripolyphosphate using ionotropic gelation technique, and to evaluate their potential capacity to arrest QS in bacteria. The resulting NPs were in the size range of 250-400 nm with CS70/5 and 330-600 nm with CS70/20, had low polydispersity index (<0.25) and highly positive zeta potential ranging from ζ ~+31 to +40 mV. Quercetin, a hydrophobic model flavonoid, could be incorporated proportionally with increasing amounts of Captisol® in the NPs formualtion, without altering significantly its physicochemical properties. Elemental analysis and FTIR studies revealed that Captisol® and quercetin were effectively integrated into the NPs. These NPs were stable in M9 bacterial medium for 7 h at 37 °C. Further, NPs containing Captisol® seem to prolong the release of associated drug. Bioassays against an E. coli Top 10 QS biosensor revealed that CS70/5 NPs could inhibit QS up to 61.12%, while CS70/20 NPs exhibited high antibacterial effects up to 88.32%. These results suggested that the interaction between NPs and the bacterial membrane could enhance either anti-QS or anti-bacterial activities.

Antimicrobial Polymers in the Nano-World

Infections are one of the main concerns of our era due to antibiotic-resistant infections and the increasing costs in the health-care sector. Within this context, antimicrobial polymers present a great alternative to combat these problems since their mechanisms of action differ from those of antibiotics. Therefore, the microorganisms' resistance to these polymeric materials is avoided. Antimicrobial polymers are not only applied in the health-care sector, they are also used in many other areas. This review presents different strategies that combine nanoscience and nanotechnology in the polymer world to combat contaminations from bacteria, fungi or algae. It focuses on the most relevant areas of application of these materials, viz. health, food, agriculture, and textiles.

Supramolecular hydrogel based on high-solid-content mPECT nanoparticles and cyclodextrins for local and sustained drug delivery

A novel injectable and high-solid-content drug-loaded supramolecular hydrogel (PTX-mPECT NP/α-CD^gel) was prepared by self-assembly of inclusion complexes based on PTX-loaded mPECT nanoparticles and α-cyclodextrin.