Emerging Nanomedicine Therapies to Counter the Rise of Methicillin-Resistant Staphylococcus aureus

Chitosan/Pectin Nanoparticles Encapsulated with Echinacea pallida: a Focus on Antibacterial and Antibiofilm Activity Against Multidrug-Resistant Staphylococcus aureus

In recent years, the alarming spread of antibiotic resistance has posed a grave global threat to public health, resulting in millions of fatalities worldwide. Multidrug-resistant (MDR) microorganisms have emerged due to the broad spread of resistance and the sharing of resistance genes between various varieties of bacteria. A promising strategy for treating difficult-to-treat bacterial infections is the development of nanomaterial-based therapeutics that could circumvent existing pathways linked to acquire drug resistance. The objectives of this study were to prepare chitosan/pectin-encapsulated Echinacea pallida (E. pallida) extract and evaluate its efficacy against MDR isolates. E. pallida extract was encapsulated into chitosan (CS)/pectin (PN) nanoparticles (NPs) using the gelation technique in the present study. The synthesized NPs were analyzed using scanning electron microscopy (SEM), dynamic light scattering (DLS), transmission electron microscopes (TEM), and Fourier transform infrared (FT-IR) spectroscopy. Antibacterial and antibiofilm activity of the nanoparticles against S. aureus has been assessed and explored. In addition, the toxicity of synthetic NPs against HEK 93 cells was evaluated. The interactions between functional groups were confirmed by FT-IR spectroscopy. The CS/PN NPs were spherical with uniform surfaces, and their dimension ranged from 80 to 110 nm. The PDI of the E. pallida extract was 0.521, and its entrapment efficiency (EE%) was 84.35%. The synthesized CS/PN NPs exhibited antibacterial and antibiofilm activity against bacteria relevant to public health. In addition, the results demonstrated that the extract-containing NPs had no toxic impact on HEK-93 cells. The findings presented here should aid the development of novel plant extracts with enhanced stability and antibacterial activity, thereby reducing the need for antibiotics.

Fighting Methicillin-Resistant Staphylococcus aureus with Targeted Nanoparticles

Antimicrobial resistance (AMR) is considered one of the greatest threats to global health. Methicillin-resistant Staphylococcus aureus (MRSA) remains at the core of this threat, accounting for about 90% of S. aureus infections widespread in the community and hospital settings. In recent years, the use of nanoparticles (NPs) has emerged as a promising strategy to treat MRSA infections. NPs can act directly as antibacterial agents via antibiotic-independent activity and/or serve as drug delivery systems (DDSs), releasing loaded antibiotics. Nonetheless, directing NPs to the infection site is fundamental for effective MRSA treatment so that highly concentrated therapeutic agents are delivered to the infection site while directly reducing the toxicity to healthy human cells. This leads to decreased AMR emergence and less disturbance of the individual's healthy microbiota. Hence, this review compiles and discusses the scientific evidence related to targeted NPs developed for MRSA treatment.

Antimicrobial resistance in methicillin-resistant staphylococcus aureus

In the medical community, antibiotics are revered as a miracle because they stop diseases brought on by pathogenic bacteria. Antibiotics have become the cornerstone of contemporary medical advancements ever since penicillin was discovered. Antibiotic resistance developed among germs quickly, placing a strain in the medical field. Methicillin-resistant Staphylococcus aureus (MRSA), Since 1961, has emerged as the major general antimicrobial resistant bacteria (AMR) worldwide. MRSA can easily transmit across the hospital system and has mostly gained resistance to medications called beta-lactamases. This enzyme destroys the cell wall of beta-lactam antibiotics resulting in resistance against that respective antibiotic. Daptomycin, linezolid and vancomycin were previously used to treat MRSA infections. However, due to mutations and Single nucleotide polymorphisms (SNPs) in Open reading frames (ORFs) and SCCmec machinery of respective antibody, MRSA developed resistance against those antibiotics. The MRSA strains (USA300, CC398, CC130 etc.), when their pan-genomes were analyzed were found the genes involved in invoking resistance against the antibiotics as well as the epidemiology of that respective strain. PENC (penicillin plus potassium clavulanate) is the new antibiotic showing potential in treatment of MRSA though it is itself resistant against penicillin alone. In this review, our main focus is on mechanism of development of AMR in MRSA, how different ORFs are involved in evoking resistance in MRSA and what is the core-genome of different antimicrobial resistant MRSA.

Targeting bacterial biofilms using vancomycin and multivalent cell-penetrating peptide labeled quantum dots

Bacterial biofilms are highly resilient microbial musters that are difficult to eradicate, driving the development of novel therapeutic strategies. The current study aims to investigate the therapeutic efficacy of cell-penetrating peptide-based targeted delivery of vancomycin functionalized quantum dots in eradicating biofilm formation in gram-positive and gram-negative bacterial strains. The conjugate was characterized using fluorimetry, UV-visible spectroscopy, gel electrophoresis, and zeta potential. The conjugate was then tested for antimicrobial and antibiofilm activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli, and it demonstrated excellent antimicrobial as well as antibiofilm activity against all the tested strains. The findings indicated that the conjugate was capable of overcoming bacterial resistance of bacteria in addition to the eradication of biofilms at effective concentrations.

Herbal Fennel Essential Oil Nanogel: Formulation, Characterization and Antibacterial Activity against Staphylococcus aureus

Antimicrobial resistance (AMR) is one of the greatest threats to humanity in the world. Antibiotic-resistant bacteria spread easily in communities and hospitals. Staphylococcus aureus (S. aureus) is a serious human infectious agent with threatening broad-spectrum resistance to many commonly used antibiotics. To prevent the spread of pathogenic microorganisms, alternative strategies based on nature have been developed. Essential oils (EOs) are derived from numerous plant parts and have been described as antibacterial agents against S. aureus. Fennel essential oils were selected as antibacterial agents encapsulated in nanoparticles of polylactic acid and glycolic acid (PLGA). The optimum size of the formulation after loading with the active ingredient was 123.19 ± 6.1595 nm with a zeta potential of 0.051 ± 0.002 (23 ± 1.15 mV). The results of the encapsulation efficiency analysis showed high encapsulation of EOs, i.e., 66.4 ± 3.127. To obtain promising carrier materials for the delivery of fennel EOs, they were incorporated in the form of nanogels. The newly developed fennel oils in PLGANPs nanogels have good drug release and MIC against S. aureus. These results indicate the potential of this novel delivery system for antimicrobial therapy.

Microbial resistance to nanotechnologies: An important but understudied consideration using antimicrobial nanotechnologies in orthopaedic implants

Microbial resistance to current antibiotics therapies is a major cause of implant failure and adverse clinical outcomes in orthopaedic surgery. Recent developments in advanced antimicrobial nanotechnologies provide numerous opportunities to effective remove resistant bacteria and prevent resistance from occurring through unique mechanisms. With tunable physicochemical properties, nanomaterials can be designed to be bactericidal, antifouling, immunomodulating, and capable of delivering antibacterial compounds to the infection region with spatiotemporal accuracy. Despite its substantial advancement, an important, but under-explored area, is potential microbial resistance to nanomaterials and how this can impact the clinical use of antimicrobial nanotechnologies. This review aims to provide a better understanding of nanomaterial-associated microbial resistance to accelerate bench-to-bedside translations of emerging nanotechnologies for effective control of implant associated infections.

Use of Nanoparticles to Prevent Resistance to Antibiotics-Synthesis and Characterization of Gold Nanosystems Based on Tetracycline

Antimicrobial resistance (AMR) is a serious public health problem worldwide which, according to the World Health Organization (WHO), requires research into new and more effective drugs. In this work, both gold nanoparticles covered with 16-3-16 cationic gemini surfactant (Au@16-3-16) and DNA/tetracycline (DNA/TC) intercalated complexes were prepared to effectively transport tetracycline (TC). Synthesis of the Au@16-3-16 precursor was carried out by using trihydrated gold, adding sodium borohydride as a reducing agent and the gemini surfactant 16-3-16 as stabilizing agent. Circular dichroism and atomic force microscopy techniques were then used to ascertain the optimal R range of the relationship between the concentrations of Au@16-3-16 and the DNA/TC complex (R = CAu@16-3-16/CDNA) that allow the obtainment of stable and compact nanosystems, these characteristics being fundamental for their use as antibiotic transporters. Stability studies over time were carried out for distinct selected Au@16-3-16 and Au@16-3-16/DNA-TC nanoformulations using the ultraviolet−visible spectrophotometry technique, checking their stability for at least one month. In addition, in order to know the charge and size distribution of the nanocomplexes, DLS and zeta potential measurements were performed in the solution. The results showed that the characterized nanosystems were highly charged, stable and of a reduced size (<100 nm) that allows them to cross bacterial membranes effectively (>1 μm). Once the different physicochemical characteristics of the gold nanosystems were measured, Au@16-3-16 and Au@16-3-16/DNA-TC were tested on Escherichia coli and Staphylococcus aureus to study their antibacterial properties and internalization capacity in microbes. Differences in the interaction of the precursors and the compacted nanosystems generated were observed in Gram-positive and Gram-negative bacteria, possibly due to membrane damage or electrostatic interaction with internalization by endocytosis. In the internalization experiments, depending on the treatment application time, the greatest bacterial destruction was observed for all nanoformulations explored at 18 h of incubation. Importantly, the results obtained demonstrate that both new nanosystems based on TC and Au@16-3-16 precursors have optimal antimicrobial properties and would be beneficial for use in patients, avoiding possible side effects.

A Metal-Containing NP Approach to Treat Methicillin-Resistant Staphylococcus aureus (MRSA): Prospects and Challenges

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of pneumonia in humans, and it is associated with high morbidity and mortality rates, especially in immunocompromised patients. Its high rate of multidrug resistance led to an exploration of novel antimicrobials. Metal nanoparticles have shown potent antibacterial activity, thus instigating their application in MRSA. This review summarizes current insights of Metal-Containing NPs in treating MRSA. This review also provides an in-depth appraisal of opportunities and challenges in utilizing metal-NPs to treat MRSA.

Overcoming Methicillin-Resistance Staphylococcus aureus (MRSA) Using Antimicrobial Peptides-Silver Nanoparticles

Antibiotics are regarded as a miracle in the medical field as it prevents disease caused by pathogenic bacteria. Since the discovery of penicillin, antibiotics have become the foundation for modern medical discoveries. However, bacteria soon became resistant to antibiotics, which puts a burden on the healthcare system. Methicillin-resistant Staphylococcus aureus (MRSA) has become one of the most prominent antibiotic-resistant bacteria in the world since 1961. MRSA primarily developed resistance to beta-lactamases antibiotics and can be easily spread in the healthcare system. Thus, alternatives to combat MRSA are urgently required. Antimicrobial peptides (AMPs), an innate host immune agent and silver nanoparticles (AgNPs), are gaining interest as alternative treatments against MRSA. Both agents have broad-spectrum properties which are suitable candidates for controlling MRSA. Although both agents can exhibit antimicrobial effects independently, the combination of both can be synergistic and complementary to each other to exhibit stronger antimicrobial activity. The combination of AMPs and AgNPs also reduces their own weaknesses as their own, which can be developed as a potential agent to combat antibiotic resistance especially towards MRSA. Thus, this review aims to discuss the potential of antimicrobial peptides and silver nanoparticles towards controlling MRSA pathogen growth.

Emerging concerns of infectious diseases and drug delivery challenges

Emerging infectious diseases are the infections that could be newly appeared or have existed demographic area with rapidly increasing in some geographic range. Among various types of emerging infectious diseases like Ebola, chikungunya, tuberculosis, SARS, MERS, avian flu, swine flu, Zika, and so on, very recently we have witnessed the emergence of recently recognized coronavirus infection as Covid-19 pandemic caused by SARS-CoV-2, which rapidly spread around the world. Various emerging factors precipitating disease emergence include environmental, demographic, or ecological that increase the contact of people with unfamiliar microbial agents or their host or promote dissemination. Here in this chapter, we reviewed the various emerging considerations of infectious diseases including factors responsible for emerging and re-emerging infectious diseases as well as drug delivery challenges to treat infectious diseases and various strategies to deal with these challenges including nanotheranostics. Nanotheranostics are showing potential toward real-time understanding, diagnosis, and monitoring the response of the chemotherapy during treatment with reduced nontarget toxicity and enhanced safety level in the recent research studies.

Nicotiana spp. for the Expression and Purification of Functional IgG3 Antibodies Directed Against the Staphylococcus aureus Alpha Toxin

Immunoglobulin subclass IgG1 is bound and neutralized effectively by Staphylococcus aureus protein A, allowing the bacterium to evade the host’s adaptive immune response. In contrast, the IgG3 subclass is not bound by protein A and can be used to treat S. aureus infections, including drug-resistant strains such as methicillin-resistant Staphylococcus aureus (MRSA). However, the yields of recombinant IgG3 are generally low because this subclass is prone to degradation, and recovery is hindered by the inability to use protein A as an affinity ligand for antibody purification. Here, we investigated plants (Nicotiana spp.) as an alternative to microbes and mammalian cell cultures for the production of an IgG3 antibody specific for the S. aureus alpha toxin. We targeted recombinant IgG3 to different subcellular compartments and tested different chromatography conditions to improve recovery and purification. Finally, we tested the antigen-binding capacity of the purified antibodies. The highest IgG3 levels in planta (&gt;130 mg kg−1 wet biomass) were achieved by targeting the endoplasmic reticulum or apoplast. Although the purity of IgG3 exceeded 95% following protein G chromatography, product recovery requires further improvement. Importantly, the binding affinity of the purified antibodies was in the nanomolar range and thus comparable to previous studies using murine hybridoma cells as the production system.

Nanomaterials and Essential Oils as Candidates for Developing Novel Treatment Options for Bovine Mastitis

Nanomaterials have been used for diagnosis and therapy in the human medical field, while their application in veterinary medicine and animal production is still relatively new. Nanotechnology, however, is a rapidly growing field, offering the possibility of manufacturing new materials at the nanoscale level, with the formidable potential to revolutionize the agri-food sector by offering novel treatment options for prevalent and expensive illnesses such as bovine mastitis. Since current treatments are becoming progressively more ineffective in resistant bacteria, the development of innovative products based on both nanotechnology and phytotherapy may directly address a major global problem, antimicrobial resistance, while providing a sustainable animal health solution that supports the production of safe and high-quality food products. This review summarizes the challenges encountered presently in the treatment of bovine mastitis, emphasizing the possibility of using new-generation nanomaterials (e.g., biological synthesized nanoparticles and graphene) and essential oils, as candidates for developing novel treatment options for bovine mastitis.

In Vivo and In Vitro Assessments of the Antibacterial Potential of Chitosan-Silver Nanocomposite Against Methicillin-Resistant Staphylococcus aureus-Induced Infection in Rats

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most threatening multidrug-resistant bacteria worldwide. Owing to their efficient antimicrobial properties, nanoparticles have been widely used as an alternative approach for combating the antibiotic-resistant bacteria. Consequently, this study was designed to compare in between the bactericidal effect of low doses (5 mg/kg bwt) of nanoparticles of chitosan (Ch-NPs), silver (Ag-NPs), and chitosan-silver nanocomposites (Ch-Ag NCs) both in vitro and in vivo against experimentally chronic infection induced by methicillin-resistant Staphylococcus aureus (MRSA). The three forms of nanoparticles were tested for their in vitro antimicrobial potential against MRSA by detection of MICs and MBCs using microdilution method. In vivo, thirty-five male albino Wistar rats were used and divided into five groups (n = 7). Group l (negative control), group 2 (MRSA infected and untreated), groups 3, 4, and 5 (MRSA infected then treated with Ch-NPs, Ag-NPs, and Ch-Ag NCs respectively for 7 days). After 6 weeks, blood samples were collected then rats were euthanized to collect different organs (liver, spleen, lungs, and kidneys). Some of them were kept in 10% formalin for histopathological investigations while others used for bacterial re-isolation. Ch-Ag NCs showed the lowest MIC and MBC among the tested nanoparticles. Moreover, the highest histopathological scoring was observed in the infected and untreated group while the lowest scoring was detected in groups treated with Ch-Ag NCs in comparison with the negative control group. The highest bacterial count was noticed in the infected and untreated group followed by those treated with Ch-NPs while the lowest count was observed in group treated with Ch-Ag NCs. Depending on these results, it can be concluded that Ch-Ag NCs have a strong bactericidal effect against MRSA and may be used as alternative option to antibiotics.

Novel approaches for the treatment of methicillin-resistant Staphylococcus aureus: Using nanoparticles to overcome multidrug resistance

Methicillin-resistant Staphylococcus aureus (MRSA) causes serious infections in both community and hospital settings, with high mortality rates. Treatment of MRSA infections is challenging because of the rapidly evolving resistance mechanisms combined with the protective biofilms of S. aureus. Together, these characteristic resistance mechanisms continue to render conventional treatment modalities ineffective. The use of nanoformulations with unique modes of transport across bacterial membranes could be a useful strategy for disease-specific delivery. In this review, we summarize treatment approaches for MRSA, including novel techniques in nanoparticulate designing for better therapeutic outcomes; and facilitate an understanding that nanoparticulate delivery systems could be a robust approach in the successful treatment of MRSA.

Nanoparticles for treatment of bovine Staphylococcus aureus mastitis

Staphylococcus aureus (S. aureus) is one of the most important zoonotic bacterial pathogens, infecting human beings and a wide range of animals, in particular, dairy cattle. Globally. S. aureus causing bovine mastitis is one of the biggest problems and an economic burden facing the dairy industry with a strong negative impact on animal welfare, productivity, and food safety. Furthermore, its smart pathogenesis, including facultative intracellular parasitism, increasingly serious antimicrobial resistance, and biofilm formation, make it challenging to be treated by conventional therapy. Therefore, the development of nanoparticles, especially liposomes, polymeric nanoparticles, solid lipid nanoparticles, nanogels, and inorganic nanoparticles, are gaining traction and excellent tools for overcoming the therapeutic difficulty accompanied by S. aureus mastitis. Therefore, in this review, the current progress and challenges of nanoparticles in enhancing the S. aureus mastitis therapy are focused stepwise. Firstly, the S. aureus treatment difficulties by the antimicrobial drugs are analyzed. Secondly, the advantages of nanoparticles in the treatment of S. aureus mastitis, including improving the penetration and accumulation of their payload drugs intracellular, decreasing the antimicrobial resistance, and preventing the biofilm formation, are also summarized. Thirdly, the progression of different types from the nanoparticles for controlling the S. aureus mastitis are provided. Finally, the difficulties that need to be solved, and future prospects of nanoparticles for S. aureus mastitis treatment are highlighted. This review will provide the readers with enough information about the challenges of the nanosystem to help them to design and fabricate more efficient nanoformulations against S. aureus infections.

Levofloxacin-loaded naturally occurring monoterpene-based nanoemulgel: a feasible efficient system to circumvent MRSA ocular infections

Staphylococcus aureus is a leading cause of ocular keratitis worldwide, and the upsurge of Methicillin-resistant Staphylococcus Aureus (MRSA) strains necessitated the development of new antimicrobial agents. D-limonene is the major constituent of oil extracted from citrus peel, which has been utilized for its gastroprotective, antifungal, antitumor, and antibacterial effects. The present study aimed to develop an effective in-situ ocular limonene-based nanoemulgel to enhance the efficacy of fluoroquinolones against MRSA associated ocular biofilm infection. The nanoemulsion composed of limonene, Tween^®80, propylene glycol at a ratio of 5:4:1 loaded with levofloxacin. The formulated levofloxacin-loaded limonene-based nanoemulsion physiochemical properties namely; droplet size, polydispersity index, zeta potential, and in-vitro drug release were studied and stability over three months was assessed. Furthermore, in-vitro antimicrobial susceptibility was investigated on biofilm-forming MRSA strain through kinetics of killing and biofilm assay. The in-situ nanoemulgel ocular irritation was studied by HET-CAM test. The results demonstrated that levofloxacin-loaded limonene-based nanoemulsion had a particle size of 119 ± 0.321 nm with improved eradicating efficacy of MRSA biofilm, where the MIC of the loaded nanoemulgel was 3.12 mg/ml significantly less than that of drug alone (6.25 mg/ml). HET-CAM test showed no signs of hemorrhage, coagulation, or lysis for the loaded nanoemulgel same as sodium chloride solution (negative control) where its irritation score was zero compared to 9.87 for the positive irritant group (1%w/v sodium lauryl sulfate). In conclusion, the current investigation provided a strong foundation for further studies of limonene nanoemulgel as a potential complementary therapeutic agent against resistant bacterial strains.

Functionalization and antimicrobial evaluation of ampicillin, penicillin and vancomycin with Pyrenacantha grandiflora Baill and silver nanoparticles

Some antibiotics have lost their efficacy over common infections and this has led to the search for new antibiotics and chemically altering existing ones for a better control of infectious diseases. In the present study, Pyrenacantha grandiflora tubers extracts were conjugated with ampicillin, penicillin, vancomycin and silver nanoparticles and their antimicrobial activity was evaluated against Escherichia coli, Staphylococcus aureus and Klebsiella Pneumoniae. The reactions were confirmed by formation of new functional groups that were identified by Fourier transmission infrared spectroscopy (FTIR). Minimum inhibitory concentrations were determined using the microdilution assay. Minimum bactericidal concentrations and the fractional inhibition concentration index were also determined. FTIR analysis indicated different functional group associated with conjugation. The activity of ampicillin was improved when conjugated with silver nanoparticles against K. pneumonia and E. coli. Vancomycin showed improvement of activity when conjugated to silver nanoparticles against K. pneumonia. Penicillin was improved by acetone extracts and vancomycin showed to be more effective when conjugated with silver nanoparticles and water extracts. The conjugation of P. grandiflora with penicillin, ampicillin and vancomycin in the presence of silver nanoparticles improved their biological activities. Therefore, the conjugates are medicinally important and can be used to improve the activity of existing antibiotics.

Tailoring Nanoparticle-Biofilm Interactions to Increase the Efficacy of Antimicrobial Agents Against Staphylococcus aureus

Background

Considering the timeline required for the development of novel antimicrobial drugs, increased attention should be given to repurposing old drugs and improving antimicrobial efficacy, particularly for chronic infections associated with biofilms. Methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) are common causes of biofilm-associated infections but produce different biofilm matrices. MSSA biofilm cells are typically embedded in an extracellular polysaccharide matrix, whereas MRSA biofilms comprise predominantly of surface proteins and extracellular DNA (eDNA). Nanoparticles (NPs) have the potential to enhance the delivery of antimicrobial agents into biofilms. However, the mechanisms which influence the interactions between NPs and the biofilm matrix are not yet fully understood.

Methods

To investigate the influence of NPs surface chemistry on vancomycin (VAN) encapsulation and NP entrapment in MRSA and MSSA biofilms, mesoporous silica nanoparticles (MSNs) with different surface functionalization (bare-B, amine-D, carboxyl-C, aromatic-A) were synthesised using an adapted Stöber method. The antibacterial efficacy of VAN-loaded MSNs was assessed against MRSA and MSSA biofilms.

Results

The two negatively charged MSNs (MSN-B and MSN-C) showed a higher VAN loading in comparison to the positively charged MSNs (MSN-D and MSN-A). Cellular binding with MSN suspensions (0.25 mg mL⁻¹) correlated with the reduced viability of both MSSA and MRSA biofilm cells. This allowed the administration of low MSNs concentrations while maintaining a high local concentration of the antibiotic surrounding the bacterial cells.

Conclusion

Our data suggest that by tailoring the surface functionalization of MSNs, enhanced bacterial cell targeting can be achieved, leading to a novel treatment strategy for biofilm infections.

Lipid-based nanosystems for targeting bone implant-associated infections: current approaches and future endeavors

Bone infections caused by Staphylococcus aureus are a major concern in medical care, particularly when associated with orthopedic-implant devices. The ability of the bacteria to form biofilms and their capacity to invade and persist within osteoblasts turn the infection eradication into a huge challenge. The reduction of antibiotic penetration through bacterial biofilms associated with the presence of persistent cells, ability to survive in the host, and high tolerance to antibiotics are some of the reasons for the difficult treatment of these infections. Effective therapeutic approaches are urgently needed. In this sense, lipid-based nanosystems, such as liposomes, have been investigated as an innovative and alternative strategy for the treatment of implant-associated S. aureus infections, due to their preferential accumulation at infected sites and interaction with S. aureus. This review highlights the recent advances on antibiotic-loaded liposome formulations both in vitro and in vivo and how the interaction with S. aureus biofilms may be improved by modulating the liposomal external surface. Graphical Abstract.

The Fabrication and in vitro Evaluation of Retinoic Acid-Loaded Electrospun Composite Biomaterials for Tracheal Tissue Regeneration

Although relatively rare, major trauma to the tracheal region of the airways poses a significant clinical challenge with few effective treatments. Bioengineering and regenerative medicine strategies have the potential to create biocompatible, implantable biomaterial scaffolds, with the capacity to restore lost tissue with functional neo-trachea. The main goal of this study was to develop a nanofibrous polycaprolactone-chitosan (PCL-Chitosan) scaffold loaded with a signaling molecule, all-trans retinoic acid (atRA), as a novel biomaterial approach for tracheal tissue engineering. Using the Spraybase® electrospinning platform, polymer concentration, solvent selection, and instrument parameters were optimized to yield a co-polymer with nanofibers of 181-197 nm in diameter that mimicked tracheobronchial tissue architecture. Thereafter, scaffolds were assessed for their biocompatibility and capacity to induce mucociliary functionalization using the Calu-3 cell line. PCL-Chitosan scaffolds were found to be biocompatible in nature and support Calu-3 cell viability over a 14 day time period. Additionally, the inclusion of atRA did not compromise Calu-3 cell viability, while still achieving an efficient encapsulation of the signaling molecule over a range of atRA concentrations. atRA release from scaffolds led to an increase in mucociliary gene expression at high scaffold loading doses, with augmented MUC5AC and FOXJ1 detected by RT-PCR. Overall, this scaffold integrates a synthetic polymer that has been used in human tracheal stents, a natural polymer generally regarded as safe (GRAS), and a drug with decades of use in patients. Coupled with the scalable nature of electrospinning as a fabrication method, all of these characteristics make the biomaterial outlined in this study amenable as an implantable device for an unmet clinical need in tracheal replacement.

Multi-functionalized nanocarriers targeting bacterial reservoirs to overcome challenges of multi drug-resistance

INTRODUCTION

Infectious diseases associated with intracellular bacteria such as Staphylococcus aureus, Salmonella typhimurium and Mycobacterium tuberculosis are important public health concern. Emergence of multi and extensively drug-resistant bacterial strains have made it even more obstinate to offset such infections. Bacteria residing within intracellular compartments provide additional barriers to effective treatment.

METHOD

Information provided in this review has been collected by accessing various electronic databases including Google scholar, Web of science, Scopus, and Nature index. Search was performed using keywords nanoparticles, intracellular targeting, multidrug resistance, Staphylococcus aureus; Salmonella typhimurium; Mycobacterium tuberculosis. Information gathered was categorized into three major sections as 'Intracellular targeting of Staphylococcus aureus, Intracellular targeting of Salmonella typhimurium and Intracellular targeting of Mycobacterium tuberculosis' using variety of nanocarrier systems.

RESULTS

Conventional management for infectious diseases typically comprises of long-term treatment with a combination of antibiotics, which may lead to side effects and decreased patient compliance. A wide range of multi-functionalized nanocarrier systems have been studied for delivery of drugs within cellular compartments where bacteria including Staphylococcus aureus, Salmonella typhimurium and Mycobacterium tuberculosis reside. Such carrier systems along with targeted delivery have been utilized for sustained and controlled delivery of drugs. These strategies have been found useful in overcoming the drawbacks of conventional treatments including multi-drug resistance.

CONCLUSION

Development of multi-functional nanocargoes encapsulating antibiotics that are proficient in targeting and releasing drug into infected reservoirs seems to be a promising strategy to circumvent the challenge of multidrug resistance. Graphical abstract.

Co-delivery of free vancomycin and transcription factor decoy-nanostructured lipid carriers can enhance inhibition of methicillin resistant Staphylococcus aureus (MRSA)

Bacterial resistance to antibiotics is widely regarded as a major public health concern with last resort MRSA treatments like vancomycin now encountering resistant strains. TFDs (Transcription Factor Decoys) are oligonucleotide copies of the DNA-binding sites for transcription factors. They bind to and sequester the targeted transcription factor, thus inhibiting transcription of many genes. By developing TFDs with sequences aimed at inhibiting transcription factors controlling the expression of highly conserved bacterial cell wall proteins, TFDs present as a potential method for inhibiting microbial growth without encountering typical resistance mechanisms. However, the efficient protection and delivery of the TFDs inside the bacterial cells is a critical step for the success of this technology. Therefore, in our study, specific TFDs against S. aureus were complexed with two different types of nanocarriers: cationic nanostructured lipid carriers (cNLCs) and chitosan-based nanoparticles (CS-NCs). These TFD-carrier nanocomplexes were characterized for size, zeta potential and TFD complexation or loading efficiency in a variety of buffers. In vitro activity of the nanocomplexes was examined alone and in combination with vancomycin, first in methicillin susceptible strains of S. aureus with the lead candidate advancing to tests against MRSA cultures. Results found that both cNLCs and chitosan-based carriers were adept at complexing and protecting TFDs in a range of physiological and microbiological buffers up to 72 hours. From initial testing, chitosan-TFD particles demonstrated no visible improvements in effect when co-administered with vancomycin. However, co-delivery of cNLC-TFD with vancomycin reduced the MIC of vancomycin by over 50% in MSSA and resulted in significant decreases in viability compared with vancomycin alone in MRSA cultures. Furthermore, these TFD-loaded particles demonstrated very low levels of cytotoxicity and haemolysis in vitro. To our knowledge, this is the first attempt at a combined antibiotic/oligonucleotide-TFD approach to combatting MRSA and, as such, highlights a new avenue of MRSA treatment combining traditional small molecules drugs and bacterial gene inhibition.

The Continuing Threat of Methicillin-Resistant Staphylococcus aureus

Staphylococcus aureus has been an exceptionally successful pathogen, which is still relevant in modern age-medicine due to its adaptability and tenacity. This bacterium may be a causative agent in a plethora of infections, owing to its abundance (in the environment and in the normal flora) and the variety of virulence factors that it possesses. Methicillin-resistant S. aureus (MRSA) strains—first described in 1961—are characterized by an altered penicillin-binding protein (PBP2a/c) and resistance to all penicillins, cephalosporins, and carbapenems, which makes the β-lactam armamentarium clinically ineffective. The acquisition of additional resistance determinants further complicates their eradication; therefore, MRSA can be considered as the first representative of multidrug-resistant bacteria. Based on 230 references, the aim of this review is to recap the history, the emergence, and clinical features of various MRSA infections (hospital-, community-, and livestock-associated), and to summarize the current advances regarding MRSA screening, typing, and therapeutic options (including lipoglycopeptides, oxazolidinones, anti-MRSA cephalosporins, novel pleuromutilin-, tetracycline- and quinolone-derivatives, daptomycin, fusidic acid, in addition to drug candidates in the development phase), both for an audience of clinical microbiologists and infectious disease specialists.

Recent advances in the treatment of pathogenic infections using antibiotics and nano-drug delivery vehicles

The worldwide misuse of antibiotics and the subsequent rise of multidrug-resistant pathogenic bacteria have prompted a paradigm shift in the established view of antibiotic and bacterial-human relations. The clinical failures of conventional antibiotic therapies are associated with lengthy detection methods, poor penetration at infection sites, disruption of indigenous microflora and high potential for mutational resistance. One of the most promising strategies to improve the efficacy of antibiotics is to complex them with micro or nano delivery materials. Such materials/vehicles can shield antibiotics from enzyme deactivation, increasing the therapeutic effectiveness of the drug. Alternatively, drug-free nanomaterials that do not kill the pathogen but target virulent factors such as adhesins, toxins, or secretory systems can be used to minimize resistance and infection severity. The main objective of this review is to examine the potential of the aforementioned materials in the detection and treatment of antibiotic-resistant pathogenic organisms.