The Effect of Prehospital Clinical Trial-Related Procedures on Scene Interval, Cognitive Load, and Error: A Randomized Simulation Study.

INTRODUCTION: Globally, very few settings have undertaken prehospital randomized controlled trials. Given this lack of experience, there is a risk that such trials in these settings may result in protocol deviations, increased prehospital intervals, and increased cognitive load, leading to error. Ultimately, this may affect patient safety and mortality. The aim of this study was to assess the effect of trial-related procedures on simulated scene interval, self-reported cognitive load, medical errors, and time to action. METHODS: This was a prospective simulation study. Using a cross-over design, ten teams of prehospital clinicians were allocated to three separate simulation arms in a random order. Simulations were: (1) Eligibility assessment and administration of freeze-dried plasma (FDP) and a hemoglobin-based oxygen carrier (HBOC), (2) Eligibility assessment and administration of HBOC, (3) Eligibility assessment and standard care. All simulations also required clinical management of hemorrhagic shock. Simulated scene interval, error rates, cognitive load (measured by NASA Task Load Index), and competency in clinical care (assessed using the Simulation Assessment Tool Limiting Assessment Bias (SATLAB)) were measured. Mean differences between simulations with and without trial-related procedures were sought using one-way ANOVA or Kruskal-Wallis test. A p-value of <0.05 within the 95% confidence interval was considered significant. RESULTS: Thirty simulations were undertaken, representing our powered sample size. The mean scene intervals were 00:16:56 for Simulation 1 (FDP and HBOC), 00:17:22 for Simulation 2 (HBOC only), and 00:14:24 for Simulation 3 (standard care). Scene interval did not differ between the groups (p = 0.27). There were also no significant differences in error rates (p = 0.28) or cognitive load (p = 0.67) between the simulation groups. There was no correlation between cognitive load and error rates (r = 0.15, p = 0.42). Competency was achieved in all the assessment criteria for all simulation groups. CONCLUSION: In a simulated environment, eligibility screening, performance of trial-related procedures, and clinical management of patients with hemorrhagic shock can be completed competently by prehospital advanced life support clinicians without delaying transport or emergency care. Future prehospital clinical trials may use a similar approach to help ensure graded and cautious implementation of clinical trial procedures into prehospital emergency care systems.

Emergency medicine doctoral education in Africa: a scoping review of the published literature.

BACKGROUND: While Africa accounts for a significant proportion of world population, and disease and injury burden, it produces less than 1% of the total research output within emergency care. Emergency care research capacity in Africa may be expanded through the development of doctoral programmes that aim to upskill the PhD student into an independent scholar, through dedicated support and structured learning. This study therefore aims to identify the nature of the problem of doctoral education in Africa, thereby informing a general needs assessment within the context of academic emergency medicine. METHODS: A scoping review, utilising an a priori, piloted search strategy was conducted (Medline via PubMed and Scopus) to identify literature published between 2011 and 2021 related to African emergency medicine doctoral education. Failing that, an expanded search was planned that focused on doctoral education within health sciences more broadly. Titles, abstracts, and full texts were screened for inclusion in duplicate, and extracted by the principal author. The search was rerun in September 2022. RESULTS: No articles that focused on emergency medicine/care were found. Following the expanded search, a total of 235 articles were identified, and 27 articles were included. Major domains identified in the literature included specific barriers to PhD success, supervision practices, transformation, collaborative learning, and research capacity improvement. CONCLUSIONS: African doctoral students are hindered by internal academic factors such as limited supervision and external factors such as poor infrastructure e.g. internet connectivity. While not always feasible, institutions should offer environments that are conducive to meaningful learning. In addition, doctoral programmes should adopt and enforce gender policies to help alleviate the gender differences noted in PhD completion rates and research publication outputs. Interdisciplinary collaborations are potential mechanisms to develop well-rounded and independent graduates. Post-graduate and doctoral supervision experience should be a recognised promotion criterion to assist with clinician researcher career opportunities and motivation. There may be little value in attempting to replicate the programmatic and supervision practices of high-income countries. African doctoral programmes should rather focus on creating contextual and sustainable ways of delivering excellent doctoral education.

Liposomes with pH responsive 'on and off' switches for targeted and intracellular delivery of antibiotics.

pH responsive drug delivery systems are one of the new strategies to address the spread of bacterial resistance to currently used antibiotics. The aim of this study was to formulate liposomes with 'On' and 'Off'' pH responsive switches for infection site targeting. The vancomycin (VCM) loaded liposomes had sizes below 100 nm, at pH 7.4. The QL-liposomes had a negative zeta potential at pH 7.4 that switched to a positive charge at acidic pH. VCM release from the liposome was quicker at pH 6 than pH 7.4. The OA-QL-liposome showed 4-fold lower MIC at pH 7.4 and 8- and 16-fold lower at pH 6.0 against both MSSA and MRSA compared to the bare drug. OA-QL liposome had a 1266.67- and 704.33-fold reduction in the intracellular infection for TPH-1 macrophage and HEK293 cells respectively. In vivo studies showed that the amount of MRSA recovered from mice treated with formulations was 189.67 and 6.33-fold lower than the untreated and bare VCM treated mice respectively. MD simulation of the QL lipid with the phosphatidylcholine membrane (POPC) showed spontaneous binding of the lipid to the bilayer membrane both electrostatic and Van der Waals interactions contributed to the binding. These studies demonstrated that the 'On' and 'Off' pH responsive liposomes enhanced the activity targeted and intracellular delivery VCM.

Novel formulation of antimicrobial peptides enhances antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA).

Antimicrobial peptides (AMPs) have the ability to penetrate as well as transport cargo across bacterial cell membranes, and they have been labeled as exceptional candidates to function in drug delivery. The aim of this study was to investigate the effectiveness of novel formulation of AMPs for enhanced MRSA activity. The strategy was carried out through the formulation of liposomes by thin-layer film hydration methodology, containing phosphatidylcholine, cholesterol, oleic acid, the novel AMP, as well as vancomycin (VCM). Characterization of the AMPs and liposomes included HPLC and LCMS for peptide purity and mass determination; DLS (size, polydispersity, zeta potential), TEM (surface morphology), dialysis (drug release), broth dilution, and flow cytometry (antibacterial activity); MTT assay, haemolysis and intracellular antibacterial studies. The size, PDI, and zeta potential of the drug-loaded AMP2-Lipo-1 were 102.6 ± 1.81 nm, 0.157 ± 0.01, and - 9.81 ± 1.69 mV, respectively, while for AMP3-Lipo-2 drug-loaded formulation, it was 146.4 ± 1.90 nm, 0.412 ± 0.05, and - 4.27 ± 1.25 mV respectively at pH 7.4. However, in acidic pH for both formulations, we observed an increase in size, PDI, and a switch to positive zeta potential, which indicated the pH responsiveness of our liposomal systems. The in vitro drug release studies demonstrated that liposomal formulations released VCM-HCl at a faster rate at pH 6.0 compared to pH 7.4. In vitro antibacterial activity against S. aureus and MRSA revealed that liposomes had enhanced activity at pH 6 compared to pH 7.4. The study revealed that the formulation can potentially be used to enhance activity and penetration of AMPs, thereby improving the treatment of bacterial infections.

Formulation and Molecular Dynamics Simulations of a Fusidic Acid Nanosuspension for Simultaneously Enhancing Solubility and Antibacterial Activity.

The aim of the present study was to formulate a nanosuspension (FA-NS) of fusidic acid (FA) to enhance its aqueous solubility and antibacterial activity. The nanosuspension was characterized using various in vitro, in silico, and in vivo techniques. The size, polydispersity index, and zeta potential of the optimized FA-NS were 265 ± 2.25 nm, 0.158 ± 0.026, and -16.9 ± 0.794 mV, respectively. The molecular dynamics simulation of FA and Poloxamer-188 showed an interaction and binding energy of -74.42 kJ/mol and -49.764 ± 1.298 kJ/mol, respectively, with van der Waals interactions playing a major role in the spontaneous binding. There was an 8-fold increase in the solubility of FA in a nanosuspension compared to the bare drug. The MTT assays showed a cell viability of 75-100% confirming the nontoxic nature of FA-NS. In vitro antibacterial activity revealed a 16- and 18-fold enhanced activity against Staphylococcus aureus (SA) and methicillin-resistant SA (MRSA), respectively, when compared to bare FA. Flowcytometry showed that MRSA cells treated with FA-NS had almost twice the percentage of dead bacteria in the population, despite having an 8-fold lower MIC in comparison to the bare drug. The in vivo skin-infected mice showed a 76-fold reduction in the MRSA load for the FA-NS treated group compared to that of the bare FA. These results show that the nanosuspension of antibiotics can enhance their solubility and antibacterial activity simultaneously.

Enhancing targeted antibiotic therapy via pH responsive solid lipid nanoparticles from an acid cleavable lipid.

An acid cleavable lipid (SA-3M) was synthesized and used to develop pH-responsive solid lipid nanoparticles (SLNs) to deliver vancomycin base (VM-FB) to acidic infection sites. The size, polydispersity index and zeta potential of VM-FB_SA-3M_SLNs were 132.9±9.1nm, 0.159±0.01 and -26±4.4mV respectively, with 57.80±1.1% encapsulation efficiency. VM-FB release was significantly faster at pH6.5 than pH7.4. In vitro antibacterial activity against methicillin-susceptible and resistant Staphylococcus aureus (MSSA and MRSA) revealed that SLNs had enhanced activity at pH6.5 than pH7.4. In vivo study showed that the amount of MRSA remaining in the skin of VM-FB_SA-3M_SLNs treated mice was approximately 22-fold lower than VM-FB treated mice. Histological investigations revealed that signs of inflammation in the skin treated with VM-FB_SA-3M_SLNs were minimal. In conclusion, this study confirmed that SA-3M can form pH-responsive SLNs capable of releasing antibiotic specifically at acidic infection sites.

High-energy ball milling of saquinavir increases permeability across the buccal mucosa.

Saquinavir (SQV), a candidate for buccal drug delivery, is limited by poor solubility. This study identified the effects of high-energy ball milling on the buccal permeability of SQV and compared it to the effects of chemical enhancers, i.e. ethylenediaminetetraacetic acid (EDTA), sodium lauryl sulfate (SLS), polyethylene glycol (PEG) and beta cyclodextrin (ß-cyclodextrin). SQV was ball milled using a high energy planetary mill (1, 3, 15 and 30 h) and permeation studies across porcine buccal mucosa were performed using franz diffusion cells. Drug was quantified by UV spectrophotometry. Both unmilled and milled SQV samples were able to permeate the buccal mucosa. Milled samples of 15 h displayed the greatest flux of 10.40 ± 1.24 µg/cm(2 )h and an enhancement ratio of 2.61. All enhancers were able to increase the buccal permeability of unmilled SQV, with SLS achieving the greatest flux (6.99 ± 0.7 µg/cm(2)) and an enhancement ratio of 1.75. However, all the milled SQV samples displayed greater permeability than SLS, the best chemical enhancer for unmilled SQV. Enhanced permeability by ball milling was attributed to reduction in particle size, formation of solid dispersions and an increase in solubility of milled samples. Microscopical evaluation revealed no significant loss in mucosal cellular integrity treated with either unmilled or milled SQV. Histological studies suggest that SQV uses both the paracellular and transcellular route of transport across the mucosa, with drug treatment having no permanent affects. High-energy ball milling was superior to the chemical enhancers studied for enhancement of SQV buccal permeation.

Comparative buccal permeability enhancement of didanosine and tenofovir by potential multifunctional polymeric excipients and their effects on porcine buccal histology.

This study identified and compared the buccal permeability properties of antiretroviral drugs, didanosine (ddI) and tenofovir (TNF), and the permeability effects of polymeric excipients - i.e. carboxymethylcellulose (CMC), sodium alginate (SA), polyacrylic acid (PAA) and polyethylene glycol (PEG) - as potential multifunctional excipients for buccal drug delivery. Permeation studies across porcine buccal mucosa were performed and the drug was quantified using UV spectrophotometry. The mean flux for both ddI (113-181 µg/cm(2)h) and TNF (40-102 µg/cm(2)h) increased linearly with increasing donor concentration. All polymeric excipients improved permeability of TNF while only PEG was effective for ddI. Permeability enhancement ratios at 20 mg/mL for ddI and TNF were 1.63 and 1.74, respectively, using PEG (0.5% w/v) and CMC (0.5% w/v), respectively. The maximum enhancement ratio of 2.13 for TNF was achieved with 4% w/v PEG. Light and transmission electron microscopy revealed no significant loss in cellular integrity of mucosa treated with either TNF or ddI alone or when coupled with PEG as a polymeric enhancer. Histomorphological observations correlated with flux values obtained for TNF and ddI alone, as well as with PEG's effects on drug mass flux. TNF and ddI have demonstrated buccal delivery potential. Selective polymeric excipients provide an effective means to increase their penetration and may serve as potential formulation multifunctional excipients in a delivery system for delivery via the buccal route.

Safety of Bioplasma FDP and Hemopure in rhesus macaques after 30% hemorrhage.

Objectives: Prehospital transfusion can be life-saving when transport is delayed but conventional plasma, red cells, and whole blood are often unavailable out of hospital. Shelf-stable products are needed as a temporary bridge to in-hospital transfusion. Bioplasma FDP (freeze-dried plasma) and Hemopure (hemoglobin-based oxygen carrier; HBOC) are products with potential for prehospital use. In vivo use of these products together has not been reported. This study assessed the safety of intravenous administration of HBOC+FDP, relative to normal saline (NS), in rhesus macaques (RM). Methods: After 30% blood volume removal and 30 minutes in shock, animals were resuscitated with either NS or two units (RM size adjusted) each of HBOC+FDP during 60 minutes. Sequential blood samples were collected. After neurological assessment, animals were killed at 24 hours and tissues collected for histopathology. Results: Due to a shortage of RM during the COVID-19 pandemic, the study was stopped after nine animals (HBOC+FDP, seven; NS, two). All animals displayed physiologic and tissue changes consistent with hemorrhagic shock and recovered normally. There was no pattern of cardiovascular, blood gas, metabolic, coagulation, histologic, or neurological changes suggestive of risk associated with HBOC+FDP. Conclusion: There was no evidence of harm associated with the combined use of Hemopure and Bioplasma FDP. No differences were noted between groups in safety-related cardiovascular, pulmonary, renal or other organ or metabolic parameters. Hemostasis and thrombosis-related parameters were consistent with expected responses to hemorrhagic shock and did not differ between groups. All animals survived normally with intact neurological function. Level of evidence: Not applicable.

The acceptability of delayed consent for prehospital emergency care research in the Western Cape province of South Africa.

BACKGROUND: Informed consent is an essential prerequisite for enrolling patients into a study. Obtaining informed consent in an emergency is complex and often impossible. Delayed consent has been suggested for emergency care research. This study aims to determine the acceptability of prehospital emergency care research with delayed consent in the Western Cape community of South Africa. METHODS: This study was an online survey of a stratified, representative sample of community members in the Western Cape province of South Africa. We calculated a powered sample size to be 385, and a stratified sampling method was employed. The survey was based on similar studies and piloted. Data were analysed descriptively. RESULTS: A total of 807 surveys were returned. Most respondents felt that enrolment into prehospital research would be acceptable if it offered direct benefit to them (n = 455; 68%) or if their condition was life-threatening and the research would identify improved treatment for future patients with a similar condition (n = 474; 70%). Similar results were appreciable when asked about the participation of their family member (n = 445; 66%) or their child (n = 422; 62%) regarding direct prospects of benefit. Overwhelmingly, respondents indicated that they would prefer to be informed of their own (n = 590; 85%), their family member's (n = 593; 84%) or their child's (n = 587; 86%) participation in a study immediately or as soon as possible. Only 35% (n = 283) agreed to retention data of deceased patients without the next of kin's consent. CONCLUSION: We report majority agreement of respondents for emergency care research with delayed consent if the interventions offered direct benefit to the research participant, if the participant's condition was life-threatening and the work held the prospect of benefit for future patients, and if the protocol for delayed consent was approved by a human research ethics committee. These results should be explored using qualitative methods.

Antidiabetic effects of Psidium x durbanensis Baijnath & Ramcharun ined. (Myrtaceae) leaf extract on streptozotocin-induced diabetes in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Psidium guajava L. leaves are used to treat diabetes in South African folkloric medicine and in other parts of the world. Psidium x durbanensis Baijnath & Ramcharun ined. (PD) is a natural sterile hybrid and congener of Psidium guajava that is expected to share the medicinal properties of the genus Psidium and is widely distributed in South Africa. AIM OF THE STUDY: This study investigates the antioxidant, antidiabetic effects, and mechanisms of action of hydro-methanolic leaf extracts of PD on streptozotocin-induced diabetes in rats. MATERIAL AND METHODS: Phytochemical constituents of hydro-methanolic extract of PD were analyzed by gas chromatography-mass spectrometry (GC-MS). Male Wistar rats 250-300 g body weight (BW) were rendered diabetic after a single intraperitoneal injection with streptozotocin, 45 mg/kg BW. The diabetic rats were treated with hydro-methanolic (20:80 v/v) leaf extracts of PD (400 mg/kg/BW) or subcutaneous injections of regular insulin (2.0U/kg/BW, bid) for 56 days. The body weights of the animals were recorded daily. Fasting blood glucose, glucose tolerance tests, and insulin resistance index were measured. The effects of the extracts on total superoxide dismutase, catalase, and reduced glutathione activities, histopathology, and gene expression of insulin receptor substrate 1 and glucose transporter 4 were determined in the liver, pancreas, and gastrocnemius muscles of the rats. RESULTS: In the acute toxicity studies, there were no signs of toxicity observed for PD up to 2000 mg/kg BW doses. Diabetic animals showed significant weight loss, elevated and reduced fasting blood glucose and insulin, respectively, impaired glucose tolerance and diminished antioxidant enzymes' activities compared to controls. Treatment with PD hydro-methanolic leaf extracts improved body weight, glucose tolerance, insulin resistance, and antioxidant enzymes but not plasma insulin in diabetic animals compared to controls, respectively. GC-MS analysis identified organic acids, alcohols, vitamins, terpenoids, and esters in the extracts. Treatment with PD improved glucose uptake by stimulating mRNA expression of GLUT 4 in gastrocnemius muscles of diabetic animals compared to the untreated control and also restored histological aberrations in the pancreas and liver of diabetic rats compared with the untreated control rats. CONCLUSION: Collectively, the present study suggests that treatment with PD leaf extracts significantly ameliorated diabetes symptoms and oxidative stress in rats, and these effects may be linked to the bioactive phytoconstituents present in the plant. This study further suggests that PD improves insulin resistance by increasing glucose uptake in gastrocnemius muscles in an insulin-independent manner.

Chitosan-Based Hydrogel for the Dual Delivery of Antimicrobial Agents Against Bacterial Methicillin-Resistant Staphylococcus aureus Biofilm-Infected Wounds.

Chronic wound infections caused by antibiotic-resistant bacteria have become a global health concern. This is attributed to the biofilm-forming ability of bacteria on wound surfaces, thus enabling their persistent growth. In most cases, it leads to morbidity and in severe cases mortality. Current conventional approaches used in the treatment of biofilm wounds are proving to be ineffective due to limitations such as the inability to penetrate the biofilm matrix; hence, biofilm-related wounds remain a challenge. Therefore, there is a need for more efficient alternate therapeutic interventions. Hydrogen peroxide (HP) is a known antibacterial/antibiofilm agent; however, prolonged delivery has been challenging due to its short half-life. In this study, we developed a hydrogel for the codelivery of HP and antimicrobial peptides (Ps) against bacteria, biofilms, and wound infection associated with biofilms. The hydrogel was prepared via the Michael addition technique, and the physiochemical properties were characterized. The safety, in vitro, and in vivo antibacterial/antibiofilm activity of the hydrogel was also investigated. Results showed that the hydrogel is biosafe. A greater antibacterial effect was observed with HP-loaded hydrogels (CS-HP; hydrogel loaded with HP and CS-HP-P; hydrogel loaded with HP and peptide) when compared to HP as seen in an approximately twofold and threefold decrease in minimum inhibitory concentration values against methicillin-resistant Staphylococcus aureus (MRSA) bacteria, respectively. Similarly, both the HP-releasing hydrogels showed enhanced antibiofilm activity in the in vivo study in mice models as seen in greater wound closure and enhanced wound healing in histomorphological analysis. Interestingly, the results revealed a synergistic antibacterial/antibiofilm effect between HP and P in both in vitro and in vivo studies. The successfully prepared HP-releasing hydrogels showed the potential to combat bacterial biofilm-related infections and enhance wound healing in mice models. These results suggest that the HP-releasing hydrogels may be a superior platform for eliminating bacterial biofilms without using antibiotics in the treatment of chronic MRSA wound infections, thus improving the quality of human health.

AB2-type amphiphilic block copolymer containing a pH-cleavable hydrazone linkage for targeted antibiotic delivery.

A novel AB2-type amphiphilic block copolymer [OA-CN-NH-(PEG)2] with hydrazone linkage was synthesized and explored for pH-triggered antibiotic delivery. Vancomycin (VCM) loaded micelles of the polymer [OA-CN-NH-(PEG)2-VCM] were spherical in shape with size, polydispersity index, zeta potential and entrapment efficiency of 130.33 ± 7.36 nm, 0.163 ± 0.009, -4.33 ± 0.55 mV and 39.61 ± 4.01% respectively. The dilution stability study exhibited no significant change in the size distribution of OA-CN-NH-(PEG)2-VCM micelles up to 320-fold dilution. An in vitro drug release assay confirmed greater release of VCM from OA-CN-NH-(PEG)2-VCM at pH 6, compared to pH 7.4. An in vitro antibacterial activity evaluation of OA-CN-NH-(PEG)2-VCM showed 2-fold enhancement in antibacterial activity of VCM after 54 h of incubation against Staphylococcus aureus (S. aureus) and methicillin-resistant S. aureus (MRSA) at acidic pH compared to physiological pH. An in vivo antibacterial activity of OA-CN-NH-(PEG)2-VCM further proved the enhanced activity of OA-CN-NH-(PEG)2-VCM against MRSA. In conclusion, micelles from pH-responsive OA-CN-NH-(PEG)2 could be utilized for site-specific delivery of VCM at the infection site.

Delivery of novel vancomycin nanoplexes for combating methicillin resistant Staphylococcus aureus (MRSA) infections.

The development of novel antibiotic systems is needed to address the methicillin-resistant Staphylococcus aureus (MRSA) infections. The aim of the study was to explore the novel nanoplex delivery method for vancomycin (VCM) against MRSA using dextran sulfate sodium salt (DXT) as a polyelectrolyte complexing agent. Nanoplexes were formulated by the self-assembling amphiphile polyelectrolyte complexation method and characterized. The size, polydispersity index (PDI), and zeta potential (ZP) of the optimized VCM nanoplexes were 84.6 ±â€¯4.248 nm, 0.449 ±â€¯0.024 and -33.0 ±â€¯4.87 mV respectively, with 90.4 ±â€¯0.77% complexation efficiency (CE %) and 62.3 ±â€¯0.23% drug loading. The in vitro (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide)tetrazolium (MTT) studies of the nanoplexes were found to be non-toxic against different mammalian cell lines tested and may confirm its biosafety. While the in vitro drug release studies demonstrated sustained slower release. The in silico study confirmed the spontaneous interaction of VCM with DXT in the presence of sodium chloride. A 6.24-fold enhancement was observed for VCM nanoplexes via in vitro antibacterial studies. Flow-cytometric analysis showed effective cell killing of 67% from VCM nanoplexes compared to 32.98% from the bare vancomycin at the minimum inhibitory concentration (MIC) of 1.25 µg/mL. The in vivo studies using BALB/c mouse skin infection model revealed that nanoplexes reduced MRSA burden by 2.3-folds compared to bare VCM. The novel nanoplexes have potential to be a promising delivery system to combat MRSA infections for improved treatment of bacterial infections.

Novel two-chain fatty acid-based lipids for development of vancomycin pH-responsive liposomes against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA).

The development of bacterial resistance against antibiotics is attributed to poor localisation of lethal antibiotic dose at the infection site. This study reports on the synthesis and use of novel two-chain fatty acid-based lipids (FAL) containing amino acid head groups in the formulation of pH-responsive liposomes for the targeted delivery of vancomycin (VAN). The formulated liposomes were characterised for their size, polydispersity index (PDI), surface charge and morphology. The drug-loading capacity, drug release, cell viability, and in vitro and in vivo efficacy of the formulations were investigated. A sustained VAN release profile was observed and in vitro antibacterial studies against S. aureus and MRSA showed superior and prolonged activity over 72 h at both pH 7.4 and 6.0. Enhanced antibacterial activity at pH 6.0 was observed for the DOAPA-VAN-Lipo and DLAPA-VAN-Lipo formulations. Flow cytometry studies indicated a high killing rate of MRSA cells using DOAPA-VN-Lipo (71.98%) and DLAPA-VN-Lipo (73.32%). In vivo studies showed reduced MRSA recovered from mice treated with formulations by four- and two-folds lower than bare VN treated mice, respectively. The targeted delivery of VAN can be improved by novel pH-responsive liposomes from the two-chain (FAL) designed in this study.

Fatty acid conjugated pyridinium cationic amphiphiles as antibacterial agents and self-assembling nano carriers.

Most of the bacteria are on the verge of becoming resistant to available potential antibiotics. Novel approaches to combat these drug resistant bacteria are turning out to be crucial. This study aimed to synthesize novel fatty acid based cationic amphiphiles (FCA) that would serve as nano-drug carrier having intrinsic antibacterial activity. Three fatty acids oleic acid, linoleic acid and linolenic acid based cationic amphiphiles were synthesized and evaluated for antibacterial activity and cytotoxicity. The application in the delivery of vancomycin (VCM) was demonstrated using oleic based cationic amphiphilic (OCA). OCA was self-assembled in aqueous media to prepare VCM loaded OCA vesicles. The particle size, polydispersity index, zeta potential and entrapment efficiency were found to be 132.9 ±â€¯2.5 nm, 0.167 ±â€¯0.02, 18.9 ±â€¯1.2 mV and 61.24 ±â€¯1.8% respectively. The images from transmission electron microscopy (TEM) revealed that the vesicles were spherical and bilayered. The release of VCM from OCA vesicles was sustained throughout the studied period of 72 h. From in vitro studies, a significant antibacterial activity was observed for all three FCAs and it was found that, VCM loaded OCA vesicles displayed indifference and synergism against Gram positive methicillin susceptible and resistant staphylococcus aureus respectively (MRSA). In contrast to minimum inhibitory concentration (MIC) of VCM against Gram negative Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa), the synthesized FCAs were more potent against both the strains, further there was no synergism observed against either of the strains when VCM was encapsulated in OCA vesicles. The synergism against MRSA was further confirmed in in vivo studies using mouse infection model. These findings therefore suggest that, FCAs can make promising nano-carrier systems for the delivery of antibiotics to treat infections caused by multi drug resistant bacteria.

A hybrid of mPEG-b-PCL and G1-PEA dendrimer for enhancing delivery of antibiotics.

The development of novel materials is essential for the efficient delivery of drugs. Therefore, the aim of the study was to synthesize a linear polymer dendrimer hybrid star polymer (3-mPEA) comprising of a generation one poly (ester-amine) dendrimer (G1-PEA) and a diblock copolymer of methoxy poly (ethylene glycol)-b-poly(ε-caprolactone) (mPEG-b-PCL) for formulation of nanovesicles for efficient drug delivery. The synthesized star polymer was characterized by FTIR, 1H and 13C NMR, HRMS, GPC and its biosafety was confirmed by MTT assays. Thereafter it was evaluated as a nanovesicle forming polymer. Vancomycin loaded nanovesicles were characterized using in vitro, molecular dynamics (MD) simulations and in vivo techniques. MTT assays confirmed the nontoxic nature of the synthesized polymer, the cell viability was 77.23 to 118.6%. The nanovesicles were prepared with size, polydispersity index and zeta potential of 52.48 ±â€¯2.6 nm, 0.103 ±â€¯0.047, -7.3 ±â€¯1.3 mV respectively, with the encapsulation efficiency being 76.49 ±â€¯2.4%. MD simulations showed spontaneous self-aggregation of the dendritic star polymer and the interaction energy between the two monomers was -146.07 ±â€¯4.92, Van der Waals interactions playing major role for the aggregates stability. Human serum albumin (HSA) binding studies with Microscale Thermophoresis (MST) showed that the 3-mPEA did not have any binding affinity to the HSA, which showed potential for long systemic circulation. The vancomycin (VCM) release from the drug loaded nanovesicles was found to be slower than bare VCM, with an 65.8% release over a period of 48 h. The in vitro antibacterial test revealed that the drug loaded nanovesicles had 8- and 16-fold lower minimum inhibitory concentration (MIC) against methicillin sensitive Staphylococcus aureus and methicillin-resistant S. aureus strains (MRSA) compared to free drug. The flow cytometry study showed 3.9-fold more dead cells of MRSA in the population when samples were treated with the drug loaded nanovesicles than the bare VCM at concentration 0.488 µg/mL. An in vivo skin infection mice model showed a 20-fold reduction in the MRSA load in the drug loaded nanovesicles treated groups compared to bare VCM. These findings confirmed the potential of 3-mPEA as a promising biocompatible effective nanocarrier for antibiotic delivery.

Novel lipids with three C18-fatty acid chains and an amino acid head group for pH-responsive and sustained antibiotic delivery.

The acidic environment at bacterial infection sites is a potential external stimulus for targeted antibiotic delivery. This paper reports new biocompatible pH-sensitive lipids (PSLs) with three hydrocarbon tails, and a head group with a secondary amine and carboxylate function for site-specific nano delivery of vancomycin (VCM). PSLs formed stable liposomes with mean vesicle diameters and polydispersity indices between 99.38 ±â€¯6.59 nm to 105.60 ±â€¯5.38 nm and 0.161 ±â€¯0.003 to 0.219 ±â€¯0.05 respectively. The zeta potential values were negative at physiological pH (7.4) and shifted towards positivity with a decrease in pH. The encapsulation efficiency and loading capacity were in the range of 29-45% and 2.8-4.5% respectively. The VCM release increased and was more sustained at acidic pH than at the physiological pH. The molecular modeling studies revealed that structural changes in lipids at acidic pH could have caused the deformation of liposome structure and subsequent fast release. In vitro antibacterial activity revealed that the minimum inhibitory concentrations (MICs) of prepared liposomes at pH 6.5 were lower than the MICs at pH 7.4 against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) respectively. In addition, in vivo antibacterial activity study performed on two of the most active formulations showed that log10 CFU/mL of MRSA recovered from TOAPA-VCM-Lipo and the TLAPA-VCM-Lipo treated mice were 1.5- and 1.8-fold lower than that found in bare VCM treated ones respectively.

Synthesis of an oleic acid based pH-responsive lipid and its application in nanodelivery of vancomycin.

Stimuli-responsive nano-drug delivery systems can optimize antibiotic delivery to infection sites. Identifying novel lipids for pH responsive delivery to acidic conditions of infection sites will enhance the performance of nano-drug delivery systems. The aim of the present investigation was to synthesize and characterize a biosafe novel pH-responsive lipid for vancomycin delivery to acidic conditions of infection sites. A pH-responsive solid lipid, N-(2-morpholinoethyl) oleamide (NMEO) was synthesized and used to prepare vancomycin (VCM)-loaded solid lipid nanoparticles (VCM_NMEO SLNs). The particle size (PS), polydispersity index (PDI), zeta potential (ZP) and entrapment efficiency (EE) of the formulation were 302.8 ±â€¯0.12 nm, 0.23 ±â€¯0.03, -6.27 ±â€¯0.017 mV and 81.18 ±â€¯0.57% respectively. The study revealed that drug release and antibacterial activity were significantly greater at pH 6.0 than at pH 7.4, while the in silico studies exposed the molecular mechanisms for improved stability and drug release. Moreover, the reduction of MRSA load was 4.14 times greater (p < 0.05) in the skin of VCM_NMEO SLNs treated mice than that of bare VCM treated specimens. Thus, this study confirmed that NMEO can successfully be used to formulate pH-responsive SLNs with potential to enhance the treatment of bacterial infections.