Design of advanced materials and nano delivery approaches for enhancing activity against Methicillin resistant Staphylococcus aureus.

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Introduction

This chapter includes a brief background to the study, indicating the status of infectious diseases and the various challenges with antibiotic therapy. It further provides details on strategic solutions to improve antibiotic therapy, the resulting aims and objectives of the study, as well as novelty of the study and the structure of the following chapters.

Background

One of the serious resistant bacteria that has become a global concern is methicillin-resistant Staphylococcus aureus (MRSA). Among the various nanoparticle drug delivery systems reported to effectively deliver antibiotics, we investigated three new approaches in this study, namely: i) nanovesicles designed from linear polymers-dendrimer hybrids (LPDH) (V-3-mPEA), ii ) pH-responsive liposome (OA-QL lipo) with on and off pH-responsive switches and iii) Fusidic acid nanosuspension (FA-NS) to effectively target and treat methicillin-susceptible and resistant Staphylococcus aureus infections.

Figure 1. Death attributable to AMR compared to major causes of death [10]

Problem statement

Aims and objectives of this study

Determine the in vitro toxicity of the synthesized 3-mPEA safety to confirm its use in biological systems. Determine the in vitro toxicity of the synthesized QL lipid safety to confirm its use in biological systems.

Novelty of the study

Perform molecular dynamics simulation of lipid QL with a model bacterial membrane to determine the binding affinity of lipids to gram-positive bacteria. This research was the first report of the delivery of an antibiotic using a linear dendrimer hybrid star polymer.

Rationale of the study

This is the first report using surfactants available in the market (Poloxamer 188) to improve the water solubility of FA. The newly designed FA-NS could stimulate research in the development of nanosuspensions for other BCS class II drugs, since more than 40% of NCEs developed in the pharmaceutical industry are practically insoluble in water, making it a great challenge to develop dosage forms.

Overview of dissertation

Roy, In vitro antimicrobial activity of nanoconjugated vancomycin against drug-resistant Staphylococcus aureus, International Journal of Pharmaceutics. Vena, Dalbavancin in the treatment of various gram-positive infections: a real-life experience, International Journal of Antimicrobial Agents.

Introduction

Graphical abstract

Book Chapter

INTRODUCTION

This chapter discusses the synthesis and application of these amphiphilic dendrimers for drug and nucleic acid delivery. Emphasis is also placed on studies that will facilitate translation of amphiphilic dendrimers into clinically used novel drug delivery systems.

CLASSIFICATION OF AMPHIPHILIC DENDRIMERS

Amphiphilic layered dendrimers
Amphiphilic diblock or Janus dendrimers
Facially amphiphilic dendrimers
APPLICATIONS IN DRUG DELIVERY
Non-stimuli-responsive (NSR) self-assembling dendrimers

Amphiphilic layered dendrimers based NSR delivery systems
Janus dendrimers based NSR delivery systems
Facially amphiphilic dendrimer based NSR delivery systems

Stimuli-responsive (SR) self-assembling dendrimers

Amphiphilic layered dendrimer based SR delivery systems
Janus dendrimer based SR delivery systems
Facially amphiphilic dendrimer based SR delivery systems

Low molecular weight dendritic amphiphiles in drug delivery

These results can be attributed to the chemical interaction between the dendritic derivatives, the drug and the elongated shape of the micelle (Movellan et al., 2014). Scanning electron microscopy analysis of dendritic derivatives encapsulating chloroquine, primaquine and rhodamine B (Movellan et al., 2014).

Fig 2. Facially amphiphilic dendrimer prepared by Thayumanavan and co-workers consisting of amphiphilic benzylic monomer with hydrophilic carboxylic group and hydrophobic dodecyl chains (Wang and Scott M Grayson, 2012)

CONCLUSION AND FUTURE PERSPECTIVE

Nature Publishing Group, 6(June), pp. 2003) 'Dendritic molecular capsules for hydrophobic compounds', Journal of the American Chemical Society, 125(50), pp. 2006) 'Dendrimer-Encapsulated Camptothecins: Increased Solubility, Cellular Uptakility, Cellular and Cellular Retention Provides Enhanced Anticancer Activity in Vitro', Cancer Research. 2005) 'Studies on PEGylated and Drug-Loaded PAMAM Dendrimers', Journal of Bioactive and Compatible Polymers, 20(1), pp. 2013) 'Self-assembled incorporation of modulated block copolymer nanostructures into phase change memory for switching power reduction' , ACS Nano, 7(3), pp. 2013) 'Modular synthesis of amphiphilic Janus glycodendrimers and their self-assembly into glycodendrimersomes and other complex architectures with bioactivity to biomedically relevant lectins', Journal of the American Chemical Society, 135(24) , pp. 2010) 'Self-Assembly of Janus Dendrimers in Uniform Dendrimersomes and Other Complex Architectures', Science. American Association for the Advancement of Science pp. 2013) 'Synthesis and characterization of multifunctional linear-dendritic block copolymer for intracellular delivery of antitumor drugs', International Journal of Pharmaceutics.

2014) 'Enzyme-triggered cascade reactions and assembly of abiotic block copolymers into micellar nanostructures', Journal of the American Chemical Society, 136(16), p. 2010) 'Glycerol-based nonionic dendritic amphiphiles: Novel excipients for the solubilization of the poorly water-soluble anticancer drug Sagopilone', European Journal of Pharmaceutic Sciences.

Introduction

Graphical abstract

Published manuscript

Abstract

Introduction

This strategy embodies some positive properties of both dendrimers and their associated linear polymers for efficient drug delivery [25, 26]. There is therefore a need to develop and implement this strategy for antibacterial delivery as it could provide a biosafe and effective drug delivery system for antibiotics. There are several reports on the administration of antimicrobial drugs using pegylated PAMAM dendrimers to form LPDHs [ 45 , 46 ].

Most dendrimer modification with the linear polymers is through PEGlyation, but we envisioned that using mPEG-b-PCL block polymer would provide a better drug delivery system since the hydrophobic PCL portion attached to the dendrimer core provides stability, mechanical will provide strength of the vesicle membrane and improved loading capacity while the mPEG shell will provide long circulation.

Materials, instrumentation and methods

Results and discussion

Aggregate numbers and Com of Mass (COM) distances between two monomers were calculated using the g_aggregate tool [63] and the in-house Tcl script, respectively. Interaction. The in vitro drug release model of the bare drug and the nanovesicle formulation is shown in Figure 7. Based on the value of the exponent n, more than one mechanism may have been involved in the drug release from the nanovesicles.

Treatment of the biofilm with bare VCM and stained with Syto9 and PI showed a slight decrease in biofilm compared to untreated (Figure 9C), with some PI emission fluorescence emanating from the slide, indicating some penetration of VCM into the biofilm and bacterial killing (Figure 9D).

Figure 2. Mass peaks distribution as determined by MALDI TOF

Conclusions

Park, Polymeric Micelles and Alternative Nanonized Delivery Vehicles for Poorly Soluble Drugs, International Journal of Pharmaceutics. Li, Self-assembly of linear dendritic diblock copolymers: from nanofibers to polymersomes, Journal of the American Chemical Society. Dhakar, Dendrimers in drug delivery, diagnosis and therapy: fundamentals and potential applications, Journal of Drug Delivery and Therapeutics.

Veillard, Non-stealth (poly(lactic acid/albumin)) and stealth (poly(lactic acid-polyethylene glycol)) nanoparticles as injectable drug carriers, Journal of Controlled Release.

Introduction

Graphical abstract

Abstract

Although antimicrobial resistance is a multifaceted problem, the limitations of conventional dosage forms have been one of the underlining contributors to antimicrobial resistance. Liposomes are one of the most widely used nano-drug delivery systems, especially for the delivery of antibiotics, due to their attractive properties, such as membrane fusion ability [12-. However, depending on the log P of the drug, it can partition between the lipid and water phases [19].

A survey of the literature shows that most reports of pH-responsive liposomes have been in the cancer field.

Materials and Methods

Evaluation of the intracellular activity of OA-QL liposomes in MRSA-infected HEK 293 was performed through a previously described method [ 68 ]. Where: n = number of colonies, f = dilution factor and v = culture plate volume 4.6.7.4 Antibacterial activity in vivo. Slides of skin sections were then prepared and stained with hematoxylin and eosin (H&E).

QL lipid with both oleate moiety and positive charge MD simulations were performed on a POPC model membrane to understand the effect of the hydrophobicity and positive charge on the bacterial membrane.

Results and Discussion

The faster release from the OA-QL liposomes at pH 6.0 than pH 7.4 could be used to effectively provide a localized release of the antibiotic. The time evolution of the COM distance between QL-OAD (Figure 6 A–D) and QL-OAP (Figure 6 E–H) revealed that OAD and OAP interacted with QL in six different time periods (Table 2). The increased activity at acidic pH of the OA-QL liposomes can be attributed to the change of the surface charge of the liposome.

The average bacterial load (log10 CFU) of the untreated and bare VCM groups was 7.58±.

Figure 1. Cell viability of A 549, MCF 7 and Hep G2 cells against various concentrations of QL lipid

Conclusion

However, storage conditions at 4oC were considered more stable as the size only increased from 109 nm to 124 nm from time zero to 90 days of storage. These data confirmed the short-term physical stability potential of the VCM-loaded OA-QL liposomes as a drug delivery system. On' and 'Off' pH-responsive switches in the liposomes improved the activity and targeted delivery of the loaded drug, as well as the elimination of the intracellular MRSA infections.

The authors thank the University of KwaZulu-Natal (UKZN), the UKZN Nanotechnology Platform, the Medical Research Council and the National Research Foundation of South Africa for financial support (NRF Grant Nos. 87790 and 88453).

The UKZN Microscopy and Microanalysis and Biomedical Resources Unit is acknowledged for technical assistance, Ms Carrin Martin for proofreading and CHPC Cape Town for its supercomputing resources. Wounds, pH Sensitive Liposomes for Targeted Delivery of Antibiotics to Sites of Localized Internal Bacterial Infections, Rutgers The State University of New Jersey-New Brunswick, 2016.

Introduction

Graphical abstract

Abstract

The development of pharmaceutical dosage forms requires an understanding of the in vitro and in vivo performance of the dosage forms. In vitro studies have proven useful because they: (a) reduce costs, (b) provide the opportunity to more directly assess product performance, and (c) offer advantages in terms of ethical considerations 41. However useful in vitro testing they may fail to replicate the results in an organism's living conditions 42 as some studies have shown that in vivo results were better than in vitro outcomes. There are also reports that in vitro studies have been effective, but when introduced into a living organism trigger a cascade of events that have proven to be toxic and incompatible with the animal43.

In addition to their physicochemical properties and in vitro and in vivo performance, understanding the basic behavior and formation mechanism of drug delivery systems is essential for formulation optimization and requires examination at spatial and sequential resolutions.

Materials and methods

The thermal profiles of the FA, physical mixture P188, and freeze-dried FA-NS were determined by DSC (Shimadzu DSC-60, Japan). A shake flask method was used to determine the solubility of FA-NS and FA in water. Excess amounts of FA and freeze-dried FA-NS were added to the milli-Q water (10 ml) and placed in a shaking incubator at a temperature of 25 oC for 24 h.

50 μL of each FA and FA-NS treated with bacterial cultures in each well was added to the flow.

Figure 2. Structure of A) monomer units of P188, B) FA (PDB:2VUF).

Results

The interaction energy components showed that the spontaneous binding between P188 and FA was largely governed by VdW interactions (Figure 7B, green line). The representative images from the trajectory revealed (Figure 6) that after the binding of FA, P188 rearranged its conformations to establish stable. The polar and nonpolar solvation energy contributions to ΔGtotal were represented by ΔGpolar and ΔGnonpolar, respectively. The P188-FA binding was largely governed by hydrophobic interactions, with ΔEvdw being the most favorable contributor. Biosafety of FA-NS was assessed by quantifying viable mammalian cells after exposure to the synthesized material.

To evaluate the efficacy of the FA-NS, the MIC values of the bare FA and FA-NS MIC values were determined relative to S.