Gentamicin encapsulation in PLA/PLGA microspheres in view of treating Brucella infections

From Polymeric Nanoformulations to Polyphenols-Strategies for Enhancing the Efficacy and Drug Delivery of Gentamicin

Gentamicin is an essential broad-spectrum aminoglycoside antibiotic that is used in over 40 clinical conditions and has shown activity against a wide range of nosocomial, biofilm-forming, multi-drug resistant bacteria. Nevertheless, the low cellular penetration and serious side effects of gentamicin, as well as the fear of the development of antibacterial resistance, has led to a search for ways to circumvent these obstacles. This review provides an overview of the chemical and pharmacological properties of gentamicin and offers six different strategies (the isolation of specific types of gentamicin, encapsulation in polymeric nanoparticles, hydrophobization of the gentamicin molecule, and combinations of gentamicin with other antibiotics, polyphenols, and natural products) that aim to enhance the drug delivery and antibacterial activity of gentamicin. In addition, factors influencing the synthesis of gentamicin-loaded polymeric (poly (lactic-co-glycolic acid) (PLGA) and chitosan) nanoparticles and the methods used in drug release studies are discussed. Potential research directions and future perspectives for gentamicin-loaded drug delivery systems are given.

Nano and microparticle drug delivery systems for the treatment of Brucella infections

Nano-based drug delivery systems are increasingly used for diagnosis, prevention and treatment of several diseases, thanks to several beneficial properties, including the ability to target specific cells or organs, allowing to reduce treatment costs and side effects frequently associated with chemotherapeutic medications, thereby improving treatment compliance of patients. In the field of communicable diseases, especially those caused by intracellular bacteria, the delivery of antibiotics targeting specific cells is of critical importance to maximize their treatment efficacy. Brucella melitensis, an intracellular obligate bacterium surviving and replicating inside macrophages is hard to be eradicated, mainly because of the low ability of antibiotics to enter these phagocityc cells . Although different antibiotics regimens including gentamicin, doxycycline and rifampicin are in fact used against the Brucellosis, no efficient treatment has been attained yet, due to the intracellular life of the respective pathogen. Nano-medicines responding to environmental stimuli allow to maximize drug delivery targeting macropages, thereby boosting treatment efficacy. Several drug delivery nano-technologies, including solid lipid nanoparticles, liposomes, chitosan, niosomes, and their combinations with chitosan sodium alginate can be employed in combination of antibiotics to successfully eradicate Brucellosis infection from patients.

Review on PLGA Polymer Based Nanoparticles with Antimicrobial Properties and Their Application in Various Medical Conditions or Infections

The rise in the resistance to antibiotics is due to their inappropriate use and the use of a broad spectrum of antibiotics. This has also contributed to the development of multidrug-resistant microorganisms, and due to the unavailability of suitable new drugs for treatments, it is difficult to control. Hence, there is a need for the development of new novel, target-specific antimicrobials. Nanotechnology, involving the synthesis of nanoparticles, may be one of the best options, as it can be manipulated by using physicochemical properties to develop intelligent NPs with desired properties. NPs, because of their unique properties, can deliver drugs to specific targets and release them in a sustained fashion. The chance of developing resistance is very low. Polymeric nanoparticles are solid colloids synthesized using either natural or synthetic polymers. These polymers are used as carriers of drugs to deliver them to the targets. NPs, synthesized using poly-lactic acid (PLA) or the copolymer of lactic and glycolic acid (PLGA), are used in the delivery of controlled drug release, as they are biodegradable, biocompatible and have been approved by the USFDA. In this article, we will be reviewing the synthesis of PLGA-based nanoparticles encapsulated or loaded with antibiotics, natural products, or metal ions and their antibacterial potential in various medical applications.

Composite Polyurethane-Polylactide (PUR/PLA) Flexible Filaments for 3D Fused Filament Fabrication (FFF) of Antibacterial Wound Dressings for Skin Regeneration

This paper addresses the potential application of flexible thermoplastic polyurethane (TPU) and poly(lactic acid) (PLA) compositions as a material for the production of antibacterial wound dressings using the Fused Filament Fabrication (FFF) 3D printing method. On the market, there are medical-grade polyurethane filaments available, but few of them have properties required for the fabrication of wound dressings, such as flexibility and antibacterial effects. Thus, research aimed at the production, characterization and modification of filaments based on different TPU/PLA compositions was conducted. The combination of mechanical (tensile, hardness), structural (FTIR), microscopic (optical and SEM), degradation (2 M HCl, 5 M NaOH, and 0.1 M CoCl₂ in 20% H₂O₂) and printability analysis allowed us to select the most promising composition for further antibacterial modification (COMP-7,5PLA). The thermal stability of the chosen antibiotic—amikacin—was tested using processing temperature and HPLC. Two routes were used for the antibacterial modification of the selected filament—post-processing modification (AMI-1) and modification during processing (AMI-2). The antibacterial activity and amikacin release profiles were studied. The postprocessing modification method turned out to be superior and suitable for wound dressing fabrication due to its proven antimicrobial activity against E. coli, P. fluorescens, S. aureus and S. epidermidis bacteria.

Encapsulation of Amikacin into Microparticles Based on Low-Molecular-Weight Poly(lactic acid) and Poly(lactic acid-co-polyethylene glycol)

The aim of this study was to fabricate novel microparticles (MPs) for efficient and long-term delivery of amikacin (AMI). The emulsification method proposed for encapsulating AMI employed low-molecular-weight poly(lactic acid) (PLA) and poly(lactic acid-co-polyethylene glycol) (PLA-PEG), both supplemented with poly(vinyl alcohol) (PVA). The diameters of the particles obtained were determined as less than 30 μm. Based on an in-vitro release study, it was proven that the MPs (both PLA/PVA- and PLA-PEG/PVA-based) demonstrated long-term AMI release (2 months), the kinetics of which adhered to the Korsmeyer-Peppas model. The loading efficiencies of AMI in the study were determined at the followings levels: 36.5 ± 1.5 μg/mg for the PLA-based MPs and 106 ± 32 μg/mg for the PLA-PEG-based MPs. These values were relatively high and draw parallels with studies published on the encapsulation of aminoglycosides. The MPs provided antimicrobial action against the Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae bacterial strains. The materials were also comprehensively characterized by the following methods: differential scanning calorimetry; gel permeation chromatography; scanning electron microscopy; Fourier transform infrared spectroscopy-attenuated total reflectance; energy-dispersive X-ray fluorescence; and Brunauer-Emmett-Teller surface area analysis. The findings of this study contribute toward discerning new means for conducting targeted therapy with polar, broad spectrum antibiotics.

Development of polycationic micelles as an efficient delivery system of antibiotics for overcoming the biological barriers to reverse multidrug resistance in Escherichia coli

Highly pathogenic Gram-negative bacteria (G-) are tenacious and pose a serious threat to public health, mainly because of three biological barriers: cell envelope blockages, biofilm protection, and macrophages shelter. One strategy to bypass the biological barriers and consequently achieve a satisfying G- bactericidal effect is to utilize polymeric micelles with superior bacterial recognition and binding capabilities. In the current study, we explored the biological barriers penetration ability of a traditional polycationic micellar system (PP-PEI) based on a copolymer of polylactide-poly (ethylene glycol)-polyethylenimine (PLA5K-PEG2K-PEI2K). Subsequently, tetracycline (TC) with good fluorescence property was encapsulated into the PLA core of the micelle (PP-PEI/TC) through hydrophobic interaction. The combination of a PEI shell and loaded antibiotic drug endowed the polycationic micelles with a greater capacity for killing drug-resistant bacteria, destructing biofilms, and eradicating intracellular bacteria, compared with free TC and micelles without the inoculation of a PEI moiety. Confocal laser scanning microscopy (CLSM) and flow cytometry illustrated that PP-PEI/TC could completely penetrate and accumulate in drug-resistant E. coli, biofilms, and infected macrophages. The efficient biological barrier penetration was elucidated as due to the strong electrostatic interactions between the polycationic PEI block and the anionic composition of the bacterial outer membrane (e.g., LPS), macrophage cell membrane (e.g., phospholipid), and extracellular polymeric substances (e.g., eDNA), which was confirmed by biolayer interferometry (BLI). Once the micellar system was bound to a negatively-charged surface, bacterial and cellular enzymes could degrade the PP-PEI core to release its antibacterial content and finally kill planktonic bacteria, bacteria over the depth of a biofilm, and/or intracellular bacteria. In vivo imaging indicated that fluorescent polycationic micelles accumulated in bacterial infection sites with strong fluorescence. In vivo antibacterial experiments showed that PP-PEI/TC could dramatically reduce the number of drug-resistant E. coli EB1-1 in the peritoneal cavity of acute peritonitis BALB/c mice compared with its counterparts. In conclusion, our study demonstrated that polycationic micelles with a PEI shell could penetrate into drug-resistant bacteria, the biofilm matrix, and infected macrophages and lead to the spatiotemporal release of antibacterial agents for the comprehensive treatment of drug-resistant relevant infections.

Demineralized bone matrix paste formulated with biomimetic PLGA microcarriers for the vancomycin hydrochloride controlled delivery: Release profile, citotoxicity and efficacy against S. aureus

Infection and resulting bone defects caused by Staphylococcus aureus is one of the major issues in orthopaedic surgeries. Vancomycin hydrochloride (VaH) is largely used to manage these events. Here, a human derived bone paste supplemented with biopolymer microcarriers for VaH sustained delivery to merge osteoinductive and antimicrobial actions is described. In detail, different emulsion formulations were tested to fabricate micro-carriers of poly-lactic-co-glycolic acid (PLGA) and hydroxyapatite (HA) by a proprietary technology (named Supercritical Emulsion Extraction). These carriers (mean size 827 ± 68 μm; loading 47 mg_VaH/g_PLGA) were assembled with human demineralized bone matrix (DBM) to obtain an antimicrobial bone paste system (250 mg/0.5 cm³ w/v, carrier/DBM). Release profiles in PBS indicated a daily drug average release of about 4 µg/mL over two weeks. This concentration was close to the minimum inhibitory concentration and able to effectively inhibit the S. aureus growth in our experimental sets. Carriers cytotoxicity tests showed absence of adverse effects on cell viability at the concentrations used for paste assembly. This approach points toward the potential of the DBM-carrier-antibiotic system in hampering the bacterial growth with accurately controlled antibiotic release and opens perspectives on functional bone paste with PLGA carriers for the controlled release of bioactive molecules.

Optimising poly(lactic-co-glycolic acid) microparticle fabrication using a Taguchi orthogonal array design-of-experiment approach

The objective of this study was to identify, understand and generate a Taguchi orthogonal array model for the formation of 10-50 μm microparticles with applications in topical/ocular controlled drug delivery. Poly(lactic-co-glycolic acid) (PLGA) microparticles were fabricated by the single emulsion oil-in-water method and the particle size was characterized using laser diffraction and scanning electronic microscopy (SEM). Sequential Taguchi L12 and L18 orthogonal array (OA) designs were employed to study the influence of ten and eight parameters, respectively, on microparticle size (response). The first optimization step using the L12 design showed that all parameters significantly influenced the particle size of the prepared PLGA microparticles with exception of the concentration of poly(vinyl alcohol) (PVA) in the hardening bath. The smallest mean particle size obtained from the L12 design was 54.39 μm. A subsequent L18 design showed that the molecular weight of PLGA does not significantly affect the particle size. An experimental run comprising of defined parameters including molecular weight of PLGA (89 kDa), concentration of PLGA (20% w/v), concentration of PVA in the emulsion (0.8% w/v), solvent type (ethyl acetate), organic/aqeuous phase ratio (1:1 v/v), vortexing speed (9), vortexing duration (60 seconds), concentration of PVA in hardening bath (0.8% w/v), stirring speed of hardening bath (1200 rpm) and solvent evaporation duration (24 hours) resulted in the lowest mean particle size of 23.51 μm which was predicted and confirmed by the L18 array. A comparable size was demonstrated during the fabrication of BSA-incorporated microparticles. Taguchi OA design proved to be a valuable tool in determining the combination of process parameters that can provide the optimal condition for microparticle formulation. Taguchi OA design can be used to correctly predict the size of microparticles fabricated by the single emulsion process and can therefore, ultimately, save time and costs during the manufacturing process of drug delivery formulations by minimising experimental runs.

Formulation of Antimicrobial Tobramycin Loaded PLGA Nanoparticles via Complexation with AOT

Tobramycin is a potent antimicrobial aminoglycoside and its effective delivery by encapsulation within nanoparticle carriers could increase its activity against infections through a combination of sustained release and enhanced uptake. Effective antimicrobial therapy against a clinically relevant model bacteria (Pseudomonas aeruginosa) requires sufficient levels of therapeutic drug to maintain a drug concentration above the microbial inhibitory concentration (MIC) of the bacteria. Previous studies have shown that loading of aminoglycoside drugs in poly(lactic-co-glycolic) acid (PLGA)-based delivery systems is generally poor due to weak interactions between the drug and the polymer. The formation of complexes of tobramycin with dioctylsulfosuccinate (AOT) allows the effective loading of the drug in PLGA-nanoparticles and such nanoparticles can effectively deliver the antimicrobial aminoglycoside with retention of tobramycin antibacterial function.

Controlled-release biodegradable nanoparticles: From preparation to vaginal applications

This study aimed to prepare poly (d,l-lactide-co-glycolide) (PLGA) nanoparticles (NPs) with chitosan (CTS) surface modification to be used as a vaginal delivery system for antimycotic drugs. Clotrimazole was encapsulated with entrapment efficiencies of 86.1 and 68.9% into Clotrimazole-PLGA-NPs (CLT-PLGA-NPs) and PLGA-NPs with CTS-modified surface (CLT-PLGA-CTS-NPs), respectively. The later NPs exhibited a larger size and higher positive zeta potential (Z potential) in comparison to unmodified NPs. In vitro release kinetic studies indicated that Clotrimazole was released in percentages of >98% from both nanoparticulate systems after 18days. Antifungal activity and mucoadhesive properties of NPs were enhanced when CTS was added onto the surface. In summary, these results suggested that Clotrimazole loaded into PLGA-CTS-NPs has great potential for vaginal applications in treating vaginal infections generated by Candida albicans.

Antimicrobial activity of a new synthetic peptide loaded in polylactic acid or poly(lactic-co-glycolic) acid nanoparticles against Pseudomonas aeruginosa, Escherichia coli O157:H7 and methicillin resistant Staphylococcus aureus (MRSA)

Nanocarrier systems are currently being developed for peptide, protein and gene delivery to protect them in the blood circulation and in the gastrointestinal tract. Polylactic acid (PLA) and poly(lactic-co-glycolic) acid (PLGA) nanoparticles loaded with a new antimicrobial GIBIM-P5S9K peptide were obtained by the double emulsion solvent extraction/evaporation method. PLA- and PLGA-NPs were spherical with sizes between 300 and 400 nm for PLA and 200 and 300 nm for PLGA and <0.3 polydispersity index as determined by dynamic light scattering and scanning electron microscopy), having the zeta potential of >20 mV. The peptide-loading efficiency of PLA-NP and PLGA-NPs was 75% and 55%, respectively. PLA- and PLGA-NPs released around 50% of this peptide over 8 h. In 10% human sera the size of peptide loaded PLA- and PLGA-NPs increased between 25.2% and 39.3%, the PDI changed from 3.2 to 5.1 and the surface charge from -7.15 to 14.6 mV. Both peptide loaded PLA- and PLGA-NPs at 0.5 μM peptide concentration inhibited the growth of Escherichia coli O157:H7 (E. coli O157:H7), methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas. aeruginosa (P. aeruginosa). In contrast, free peptide inhibited at 10 μM but did not inhibit at 0.5 and 1 μM. These PLA- and PLGA-NPs presented <10% hemolysis indicating that they are hemocompatible and promising for delivery and protection system of GIBIM-P5S9K peptide.

Enhanced efficacy of clindamycin hydrochloride encapsulated in PLA/PLGA based nanoparticle system for oral delivery

Clindamycin hydrochloride (CLH) is a clinically important oral antibiotic with wide spectrum of antimicrobial activity that includes gram-positive aerobes (staphylococci, streptococci etc.), most anaerobic bacteria, Chlamydia and certain protozoa. The current study was focused to develop a stabilised clindamycin encapsulated poly lactic acid (PLA)/poly (D,L-lactide-co-glycolide) (PLGA) nano-formulation with better drug bioavailability at molecular level. Various nanoparticle (NPs) formulations of PLA and PLGA loaded with CLH were prepared by solvent evaporation method varying drug: polymer concentration (1:20, 1:10 and 1:5) and characterised (size, encapsulation efficiency, drug loading, scanning electron microscope, differential scanning calorimetry [DSC] and Fourier transform infrared [FTIR] studies). The ratio 1:10 was found to be optimal for a monodispersed and stable nano formulation for both the polymers. NP formulations demonstrated a significant controlled release profile extended up to 144 h (both CLH-PLA and CLH-PLGA). The thermal behaviour (DSC) studies confirmed the molecular dispersion of the drug within the system. The FTIR studies revealed the intactness as well as unaltered structure of drug. The CLH-PLA NPs showed enhanced antimicrobial activity against two pathogenic bacteria Streptococcus faecalis and Bacillus cereus. The results notably suggest that encapsulation of CLH into PLA/PLGA significantly increases the bioavailability of the drug and due to this enhanced drug activity; it can be widely applied for number of therapies.

Design and evaluation of antibiotic releasing self- assembled scaffolds at room temperature using biodegradable polymer particles

Biodegradable polymer-based drug-eluting implants offer many advantages such as predictable drug release kinetics, safety, and acceptable drug loading under ambient conditions. Herein, we describe fabrication and evaluation of antibiotic loaded scaffolds for localized delivery and tissue engineering applications. PDLLA particles entrapping gentamycin were formulated using solvent evaporation method and used for scaffold fabrication. Optimization of formulation parameters such as pH of the internal aqueous phase and combination of excipients like glycerol, polyvinyl alcohol (PVA) resulted in high entrapment efficiencies up to 96% of gentamicin in particles with drug load of 16-18μg/mg of polymer particles. These microparticles were fused in presence of methanol at ambient temperatures to form scaffolds of different geometry having reasonable mechanical strength. Porosity of these scaffolds was found to be more than 80%. Antibiotic released from the scaffolds was found to be bioactive as tested against Staphylococcus aureus and the release pattern was biphasic over a period of one week. The scaffolds were found to be non-toxic to murine fibroblasts cultures in vitro as well as to mice upon subcutaneous implantation. This method provides a novel and easy way of fabricating antibiotic loaded polymer scaffolds for varieties of applications.

Antifungal efficacy of amphotericin B encapsulated fibrin microsphere for treating Cryptococcus neoformans infection in Swiss albino mice

A natural and biocompatible fibrin microsphere is one of the most promising dual delivery vehicle as compared to other traditionally designed delivery modalities. It represents sustained delivery of encapsulated drug and is easily biodegradable in the blood circulation. In the present study, we evaluated the systemic augmentation of the antifungal activity of amphotericin B loaded in fibrin microsphere (AMB-fibrin microsphere) against cryptococcosis in Swiss albino mice. Mice infected with Cryptococcus neoformans were treated with 0.5mg/kg AMB-fibrin microsphere that was given alternately for 7 days. The antifungal potential of AMB-fibrin microsphere was assessed on the basis of reduction of cfu count in the systemic circulation and various vital organs of infected mice. The formulation was found to be highly effective in reducing intracellular pathogen from the experimental animals where fibrin microsphere significantly controlled the release of amphotericin B for longer time duration. The AMB-fibrin microsphere chemotherapy was significantly more effective than free amphotericin B in reducing the fungal burden and showed better survival efficacy (p<0.05). The current study demonstrating the use of novel amphotericin B loaded fibrin microsphere not only imparts protection to the encapsulated amphotericin B but also offers an effective strategy to decrease the drug associated toxicities.

Characteristics, interactions and coating adherence of heterogeneous polymer/drug coatings for biomedical devices

With this rise in surgical procedures it is important to focus on the mobility and safety of the patient and reduce the infections that are associated with hip replacements. We examine the mechanical properties of gentamicin sulphate as a model antimicrobial layer for titanium-alloy based prosthetic hips to help prevent methicillin-resistant Staphylococcus aureus infection after surgery. A top layer of poly(lactic-co-glycolic acid) is added to maintain the properties of the gentamicin sulphate as well as providing a drug delivery system. Through the use of nanoindentation and micro-scratch techniques it is possible to determine the mechanical and adhesive properties of this system. Nanoindentation determined the modulus values for the poly(lactic-co-glycolic acid) and gentamicin sulphate materials to be 8.9 and 5.2GPa, respectively. Micro-scratch established that the gentamicin sulphate layer is strongly adhered to the Ti alloy and forces of 30N show no cohesive or adhesive failure. It was determined that the poly(lactic-co-glycolic acid) is ductile in nature and delaminates from the gentamicin sulphate layer of at 0.5N.

Parenteral immunization of PLA/PLGA nanoparticle encapsulating outer membrane protein (Omp) from Aeromonas hydrophila: Evaluation of immunostimulatory action in Labeo rohita (rohu)

Advanced vaccine research approaches needs to explore on biodegradable nanoparticles (NPs) based vaccine carrier that can serve as antigen delivery systems as well as immuno-stimulatory action to induce both innate and adaptive immune response in fish. Immunogenicity of PLA and PLGA NPs encapsulating outer membrane protein (Omp) antigen of Aeromonas hydrophila were evaluated through intra-peritoneal injection in fish, Labeo rohita. Antigen loaded PLA-Omp (223.5 ± 13.19 nm) and PLGA-Omp (166.4 ± 21.23 nm) NPs were prepared using double emulsion method by efficiently encapsulating the antigen reaching the encapsulation efficiency 44 ± 4.58% and 59.33 ± 5.13% respectively. Our formulated PLA Omp and PLGA-Omp NPs were in nanometer range (<500 nm) and could be successfully endocyted in the body. Despite low antigen loading in PLA-Omp, it showed considerably slower antigen release in vitro than PLGA-Omp NPs. Other physical properties like zetapotential values and poly dispersity index (PDI) confirmed the stability as well as monodisperse nature of the formulated nanoparticles. The spherical and isolated nature of PLA-Omp and PLGA-Omp NPs were revealed by SEM analysis. Upon immunization of all antigenic formulations (PLA-Omp NP, PLGA-Omp NP, FIA-Omp, PLA NP, PLGA NP, PBS as control), significant higher bacterial agglutination titre and haemolytic activity were observed in case of PLA-Omp and PLGA-Omp immunized groups than rest groups at both 21 days and 42 days. The specific antibody response was significantly increased and persisted up to 42 days of post immunization by PLA-Omp, PLGA-Omp, FIA-Omp. PLA-Omp NPs showed better immune response (higher bacterial agglutination titre, haemolytic activity, specific antibody titre, higher percent survival upon A. hydrophila challenge) than PLGA-Omp in L. rohita confirming its better efficacy. Comparable antibody response of PLA-Omp and PLGA-Omp with FIA-Omp treated groups suggested that PLA and PLGA could be replacement for Freund's adjuvant (for stimulating antibody response) to overcome many side effects offering long lasting immunity. Our encouraging results suggest that PLA/PLGA nanoparticles based delivery system could be a novel antigen carrier for parenteral immunization in fish.

Preclinical Development and In Vivo Efficacy of Ceftiofur-PLGA Microparticles

Drug delivery systems based on polymeric microparticles represent an interesting field of development for the treatment of several infectious diseases for humans and animals. In this work, we developed PLGA microparticles loaded with ceftiofur (PLGA-cef), a third- generation cephalosporin that is used exclusively used in animals. PLGA-cef was prepared by the double emulsion w/o/w method, and exhibited a diameter in the range of 1.5–2.2 μm, and a negative ζ potential in the range of -35 to -55 mV. The loading yield of PLGA-cef was ~7% and encapsulation efficiency was approximately 40%. The pharmacokinetic study demonstrated a sustained release profile of ceftiofur for 20 days. PLGA-cef administrated in a single dose was more effective than ceftiofur non-encapsulated in rats challenged with S. Typhimurium. The in vivo toxicological evaluation showed that PLGA-cef did not affect the blood biochemical, hematological and hemostasis parameters. Overall, the PLGA-cef showed slow in vivo release profile, high antibacterial efficacy, and low toxicity. The results obtained supports the safe application of PLGA-cef as sustained release platform in the veterinary industry.

Nanocapsules loaded with iron-saturated bovine lactoferrin have antimicrobial therapeutic potential and maintain calcium, zinc and iron metabolism

AIM

This study aimed to evaluate the potential antimicrobial efficacy of alginate gel-encapsulated ceramic nanocarriers loaded with iron-saturated bovine lactoferrin (Fe-bLf) nanocarriers/nanocapsules (AEC-CP-Fe-bLf NCs).

MATERIALS & METHODS

The antimicrobial activities of non-nanoformulated apo (iron free), Fe-bLf and native forms of Australian bLf against pathogenic Salmonella typhimurium (wild strain) were studied in vitro. The efficacy of AEC-CP-Fe-bLf NCs were checked in vivo using Balb/c mice model.

RESULTS

The study revealed that native bLf is more effective in combating infection than the conventional drug ciprofloxacin (0.4 mg/ml). The efficacy of the drug was also revealed in vivo when BALB/c mice that, after being challenged with S. typhimurium (200 μl of 10(8) CFU/ml suspension), were fed orally with a nanoformulated bLf diet and the infection was observed to be eliminated. However, chronic infection developed in the group of infected mice that did not receive any drug treatment, as well as the mice treated with ciprofloxacin. The immune response to bacterial infection and to various drug treatments thereafter was studied in the mice.

CONCLUSION

The study concludes that bLf and nanoformulated Fe-bLf are more effective in the treatment of Salmonella-infected mice than ciprofloxacin.

Biodegradable uniform microspheres based on solid-in-oil-in-water emulsion for drug delivery: A comparison of homogenization and fluidic device

Based on solid-in-oil-in-water emulsification, we fabricated biodegradable poly(ϵ-caprolactone) microspheres containing gentamicin using conventional homogenization and a fluidic device. The feasibility of the poly(ϵ-caprolactone) microspheres as drug carriers was evaluated in terms of encapsulation efficiency, release behavior of gentamicin, and antimicrobial activity. The poly(ϵ-caprolactone) microspheres prepared using a fluidic device (fluidic device microspheres) had a uniform diameter and a smooth surface, whereas the poly(ϵ-caprolactone) microspheres prepared using conventional homogenization (conventional homogenization microspheres) exhibited polydisperse and a porous structure. At 0.3 wt% of gentamicin concentration, the encapsulation efficiencies of the conventional homogenization and fluidic device microspheres were 39.5% and 72.0%, respectively. In addition, a significant amount of gentamicin was only released initially from the conventional homogenization microspheres, whereas the fluidic device microspheres released gentamicin in a sustained manner for 28 days. These results confirmed the superior performances of the uniform fluidic device microspheres for drug delivery system. We further proposed a model for microsphere formation to explain the difference in performance of the conventional homogenization and fluidic device microspheres.

Effects of antibiotic physicochemical properties on their release kinetics from biodegradable polymer microparticles

PURPOSE

This study investigated the effects of the physicochemical properties of antibiotics on the morphology, loading efficiency, size, release kinetics, and antibiotic efficacy of loaded poly(DL-lactic-co-glycolic acid) (PLGA) microparticles (MPs) at different loading percentages.

METHODS

Cefazolin, ciprofloxacin, clindamycin, colistin, doxycycline, and vancomycin were loaded at 10 and 20 wt% into PLGA MPs using a water-in-oil-in water double emulsion fabrication protocol. Microparticle morphology, size, loading efficiency, release kinetics, and antibiotic efficacy were assessed.

RESULTS

The results from this study demonstrate that the chemical nature of loaded antibiotics, especially charge and molecular weight, influence the incorporation into and release of antibiotics from PLGA MPs. Drugs with molecular weights less than 600 Da displayed biphasic release while those with molecular weights greater than 1,000 Da displayed triphasic release kinetics. Large molecular weight drugs also had a longer delay before release than smaller molecular weight drugs. The negatively charged antibiotic cefazolin had lower loading efficiency than positively charged antibiotics. Microparticle size appeared to be mainly controlled by fabrication parameters, and partition and solubility coefficients did not appear to have an obvious effect on loading efficiency or release. Released antibiotics maintained their efficacy against susceptible strains over the duration of release. Duration of release varied between 17 and 49 days based on the type of antibiotic loaded.

CONCLUSIONS

The data from this study indicate that the chemical nature of antibiotics affects properties of antibiotic-loaded PLGA MPs and allows for general prediction of loading and release kinetics.

Microparticles prepared from sulfenamide-based polymers

Polysulfenamides (PSN), with a SN linkage (RSNR2) along the polymer backbone, are a new class of biodegradable and biocompatible polymers. These polymers were unknown prior to 2012 when their synthesis and medicinally relevant properties were reported. The aim of this study was to develop microparticles as a controlled drug delivery system using polysulfenamide as the matrix material. The microparticles were prepared by a water-in-oil-in-water double-emulsion solvent-evaporation method. For producing drug-loaded particles, FITC-dextran was used as a model hydrophilic compound. At the optimal formulation conditions, the external morphology of the PSN microparticles was examined by scanning electron microscopy to show the formation of smooth-surfaced spherical particles with low polydispersity. The microparticles had a net negative surface charge (-23 mV) as analyzed by the zetasizer. The drug encapsulation efficiency of the particles and the drug loading were found to be dependent on the drug molecular weight, amount of FITC-dextran used in fabricating FITC-dextran-loaded microparticles, concentration of PSN and surfactant, and volume of the internal and external water phases. FITC-dextran was found to be distributed throughout the PSN microparticles and was released in an initial burst followed by more continuous release over time. Confocal laser scanning microscopy was used to qualitatively observe the cellular uptake of PSN microparticles and indicated localization of the particles in both the cytoplasm and the nucleus.

Microcosmic mechanisms for protein incomplete release and stability of various amphiphilic mPEG-PLA microspheres

The microcosmic mechanisms of protein (recombinant human growth hormone, rhGH) incomplete release and stability from amphiphilic poly(monomethoxypolyethylene glycol-co-D,L-lactide) (mPEG-PLA, PELA) microspheres were investigated. PELA with different hydrophilicities (PELA-1, PELA-2, and PELA-3) based on various ratios of mPEG to PLA were employed to prepare microspheres exhibiting a narrow size distribution using a combined double emulsion and premix membrane emulsification method. The morphology, rhGH encapsulation efficiency, in vitro release profile, and rhGH stability of PELA microspheres during the release were characterized and compared in detail. It was found that increasing amounts of PLA enhanced the encapsulation efficiency of PELA microspheres but reduced both the release rate of rhGH and its stability. Contact angle, atomic force microscope (AFM), and quartz crystal microbalance with dissipation (QCM-D) techniques were first combined to elucidate the microcosmic mechanism of incomplete release by measuring the hydrophilicity of the PELA film and its interaction with rhGH. In addition, the pH change within the microsphere microenvironment was monitored by confocal laser scanning microscopy (CLSM) employing a pH-sensitive dye, which clarified the stability of rhGH during the release. These results suggested that PELA hydrophilicity played an important role in rhGH incomplete release and stability. Thus, the selection of suitable hydrophilic polymers with adequate PEG lengths is critical in the preparation of optimum protein drug sustained release systems. This present work is a first report elucidating the microcosmic mechanisms responsible for rhGH stability and its interaction with the microspheres. Importantly, this research demonstrated the application of promising new experimental methods in investigating the interaction between biomaterials and biomacromolecules, thus opening up a range of exciting potential applications in the biomedical field including drug delivery and tissue regeneration.

Vaccine potential of cytosolic proteins loaded fibrin microspheres of Cryptococcus neoformans in BALB/c mice

Cryptococcosis is a leading mycological cause of mortality among immunologically compromised individuals. In order to develop an effective vaccine against Cryptococcus neoformans, the cytosolic proteins (Cp) of the pathogen have been used as an antigen in combination with different formulations. In the present study, we have demonstrated that Cp encapsulated poly-lactide co-glycolide (PLGA) microsphere further co-encapsulated into the biocompatible fibrin cross-linked plasma beads (Fib-PLGA-Cp) mediated cytosolic delivery elicited strong immune response in the BALB/c mice. In contrast, other formulations of Cp failed to impart significant level of protection. The immune response, involved with Fib-PLGA-Cp protection, appear to interact with the target cells by both endocytosis as well as membrane fusion mode, thus helping in the activation of both CD4(+) and CD8(+) T-cells. Analysis of cytokine profiles in immunized animals revealed that the protective response was associated with the Th1/Th2 polarization in favor of type-1 cytokine [interferons (IFN)-γ and interleukin (IL)-2] cells. Furthermore, vaccination with Fib-PLGA-Cp elicited high immunoglobulin (Ig) G(l) and IgG(2a) isotype response; successfully cleared fungal burden in vital organs and also increased the survival rate of immunized animals. Altogether the present study is a clear indicative of the possible use of fibrin microsphere-based targeted delivery of cytosolic proteins to induce protective immune responses against experimental murine cryptococcosis.

Doxycycline-rifampin versus doxycycline-rifampin-gentamicin in treatment of human brucellosis

This prospective, non-randomized trial, compared the efficacy and tolerance of a doxycycline-rifampin regimen, administered for 45 days, versus doxycycline-rifampin given for 45 days plus gentamicin for the first 7–10 days, in the treatment of human brucellosis. Of 238 patients that were initially included in the study, 181 were finally evaluated. Ninety-four were treated with the doxycycline-rifampin and 87 with the doxycycline-rifampin-gentamicin regimens. In the doxycycline-rifampin group: relapses were noted in 13 (13.8%) patients; therapeutic failures in five (5.3%); and mild adverse effects in 28 (29.8%). In the doxycycline-rifampin-gentamicin group: four (4.6%) relapsed; and five (5.7%) therapeutic failures were registered. Mild adverse effects were registered in 29 (33.3%) patients. The doxycycline-rifampin-gentamicin regimen demonstrated a significantly lower relapse rate compared to the doxycycline-rifampin combination ( P = 0.034). We conclude that adding gentamicin for the first 7–10 days to the standard oral doxycycline-rifampin regimen can decrease the rate of relapses.

Lung-targeted delivery system of curcumin loaded gelatin microspheres

The purpose of the study is to design and evaluate curcumin loaded gelatin microspheres (C-GMS) for effective drug delivery to the lung. C-GMS was prepared by the emulsification-linkage technique and the formulation was optimized by orthogonal design. The mean encapsulation efficiency and drug loading of the optimal C-GMS were 75.5 ± 3.82 % and 6.15 ± 0.44%, respectively. The C-GMS presented a spherical shape and smooth surface with a mean particle diameter of 18.9 μm. The in vitro drug release behavior of C-GMS followed the first-order kinetics. The tissue distribution showed that the drug concentrations at lung tissue for the C-GMS suspension were significantly higher than those for the curcumin solution, and the Ce for lung was 36.19. Histopathological studies proved C-GMS was efficient and safe to be used as a passive targeted drug delivery system to the lung. Hence, C-GMS has a great potential for the targeted delivery of curcumin to the lung.

"Nanoantibiotics": a new paradigm for treating infectious diseases using nanomaterials in the antibiotics resistant era

Despite the fact that we live in an era of advanced and innovative technologies for elucidating underlying mechanisms of diseases and molecularly designing new drugs, infectious diseases continue to be one of the greatest health challenges worldwide. The main drawbacks for conventional antimicrobial agents are the development of multiple drug resistance and adverse side effects. Drug resistance enforces high dose administration of antibiotics, often generating intolerable toxicity, development of new antibiotics, and requests for significant economic, labor, and time investments. Recently, nontraditional antibiotic agents have been of tremendous interest in overcoming resistance that is developed by several pathogenic microorganisms against most of the commonly used antibiotics. Especially, several classes of antimicrobial nanoparticles (NPs) and nanosized carriers for antibiotics delivery have proven their effectiveness for treating infectious diseases, including antibiotics resistant ones, in vitro as well as in animal models. This review summarizes emerging efforts in combating against infectious diseases, particularly using antimicrobial NPs and antibiotics delivery systems as new tools to tackle the current challenges in treating infectious diseases.

Intra-discal vancomycin-loaded PLGA microsphere injection for MRSA discitis: an experimental study

OBJECTIVE

To prepare the vancomycin hydrochloride (VA)-loaded poly lactic acid-glycolic acid (PLGA) copolymer microsphere by the multiple emulsion method and evaluate its therapeutic effects on infective discitis.

METHODS

Firstly, the particle diameter distribution, shape, encapsulation efficiency, drug-loaded dosage and release curve of VA-PLGA microspheres were evaluated in vitro. Rabbits with methicillin-resistant Staphylococcus aureus infective discitis were treated with VA-PLGA intra-discal injection. Meanwhile, VA intravenous injection, blank PLGA microspheres intra-discal injection served as controls. Thirty days later, therapeutic effects were evaluated through X-ray radiophotography, histopathological and bacteriological examination.

RESULTS

Mean particle diameter was between 61.57 ± 4.37 and 67.45 ± 8.13 μm, and mean encapsulation efficiency was between 60.20 ± 1.61 and 75.27 ± 1.60 %m/m. In vitro release experiment showed that the release time was over 30 days. The result of in vivo experiment showed that inflammatory reaction in the VA-PLGA intra-discal injection group was milder than the intravenous injection group (P < 0.05), also with less inflammation. The bacterial count was also significantly lower (1.02 × 10(3) ± 1.22 × 10(3) CFU/g) than the intravenous injection group (7.51 × 10(4) ± 7.16 × 10(4) CFU/g) (P < 0.05). Besides these data, the amount used in VA-PLGA intra-discal injection group is about 20 mg, and that used in the intravenous injection group is about 2.4 g. So, we just use 1/120 of VA i.v. to obtain the better results with our microparticles.

CONCLUSION

Intra-discal injection with VA-PLGA sustained-release microspheres can use much less dosage, and effectively control and reduce infective discitis, and the therapeutic effect is superior to that of intravenous injection. A need for the clinical trials will be carried out in the near future.

Preparation and characteristics of erythromycin microspheres for lung targeting

BACKGROUND

If erythromycin is micronized into microspheres with suitable particle size, it can improve pulmonary drug concentration to maximize its effectiveness and minimize the adverse side effects.

AIM

In this study, erythromycin gelatin microspheres (EM-GMS) were prepared and some characteristics of EM-GMS were investigated. The drug-targeting index (DTI) of EM-GMS was evaluated to predict their potential as a targeted delivery system.

METHOD

Erythromycin was microencapsulated with gelatin by a double emulsion solvent evaporation method. Some characteristics of EM-GMS, including morphology, particle size, in vitro release, and safety were researched.

RESULTS

EM-GMS had a spherical shape and smooth surface morphology. The drug loading and encapsulation efficiency of EM-GMS were 13.56 +/- 0.25% and 55.82 +/- 2.23%, respectively. The release of erythromycin from EM-GMS showed an initial burst and following a sustained release, with an accumulate release of 80% at 4 hours. The EM-GMS was safe since there was no vein irritation and no hemolysis on the erythrocyte of rabbit at 3.5 mg/mL and a LD50 of 173.07 mg/kg. After administering EM-GMS to rabbits, the concentration of erythromycin in lung was 15.92 times higher than that in plasma and the DTI of EM-GMS in lung was 6.65 as compared with erythromycin lactobionate.

CONCLUSIONS

The preparation technology of EM-GMS for lung targeting was successful and the quality of microspheres was good.

Development of a novel AMX-loaded PLGA/zein microsphere for root canal disinfection

The aim of this study was to develop polymeric biodegradable microspheres (MSs) of poly(D-L lactide-co-glycolide) (PLGA) and zein capable of delivering amoxicillin (AMX) at significant levels for root canal disinfection. PLGA/zein MSs were prepared using a spray-drying technique. The systems were characterized in terms of particle size, morphology, drug loading and in vitro release. Drug levels were reached to be effective during the intracanal dressing in between visits during the endodontic treatment. In vitro release studies were carried out to understand the release profile of the MSs. Antimicrobial activity of AMX was performed by antibiograms. Enterococcus faecalis was the bacteria selected due to its prevalence in endodontic failure. Drug microencapsulation yielded MSs with spherical morphology and an average particle size of between 5 and 38 µm. Different drug-release patterns were obtained among the formulations. Release features related to the MSs were strongly dependent on drug nature as it was demonstrated by using a hydrophobic drug (indomethacin). Finally, AMX-loaded MSs were efficient against E faecalis as demonstrated by the antibiogram results. In conclusion, PLGA/zein MSs prepared by spray drying may be a useful drug delivery system for root canal disinfection.

Cephalexin microspheres for dairy mastitis: effect of preparation method and surfactant type on physicochemical properties of the microspheres

The aim of this study was to evaluate the effects of preparation method and the type of surfactant on the properties of cephalexin (CPX) microspheres in order to obtain delivery systems suitable for the treatment of dairy mastitis. Microspheres were obtained using various preparation conditions and their physicochemical characteristics such as size, loading efficiency, morphology, and drug crystallinity were investigated. Antibacterial activity of microspheres from the optimum preparation condition was also studied. CPX microspheres were prepared by two different W/O/W emulsion solvent evaporation methods using PLGA as a matrix forming polymer. Several types of surfactants including nonionic, cationic, and anionic at different concentrations were used for preparation of the particles. The type and concentration of surfactant did neither affect the size nor morphology of the microspheres but showed a pronounced effect on the CPX encapsulation efficiency. It was found that Tween 80 showed the highest drug encapsulation efficiency (66.5%). Results from X-ray diffraction diffractograms and differential scanning calorimetry thermograms indicated that CPX entrapped in these microparticles was amorphous. Assessment of antibacterial activity showed that the obtained CPX microspheres exhibited good inhibition with minimum inhibitory concentration and minimum bactericidal concentration values of 128 microg/mL and 2,048 mg/mL against Staphylococcus aureus ATCC 25923, 512 microg/mL and 4,096 mg/mL against Escherichia coli ATCC 25922, respectively.