Poly(amidoamine) dendrimer-mediated synthesis and stabilization of silver sulfonamide nanoparticles with increased antibacterial activity

Dynamic high pressure microfluidization-assisted extraction of plant active ingredients: a novel approach

The extraction method has a great influence on the yield, quality, chemical structure, and biological activities of active ingredients. Safe and efficient extraction of active ingredients is one of the important problems facing the food and pharmaceutical industry. As a pretreatment approach for the extraction of active ingredients, dynamic high pressure microfluidization (DHPM) is a promising strategy that can not only effectively increase the yield of active ingredients but also strengthen the bioactivities of active ingredients, and take the advantages of mild operating temperature and environmental friendliness. In this review, the research progress of DHPM-assisted extraction of active ingredients from plant materials in recent ten years is overviewed. The DHPM equipment, strengthening mechanism, operating procedure, critical factors and application of DHPM-assisted extraction are introduced in detail, together with the advantages and disadvantages. Furthermore, its future development trend is discussed at the end. DHPM-assisted extraction is considered as the ideal technique of better homogenization effects, less solvent consumption, more reliable operation, and so on, making it a promising method to acquire active ingredients efficiently. Therefore, this technique is worthy of further theoretical research and experimental operation.

Silver Nanoparticles: Bactericidal and Mechanistic Approach against Drug Resistant Pathogens

This review highlights the different modes of synthesizing silver nanoparticles (AgNPs) from their elemental state to particle format and their mechanism of action against multidrug-resistant and biofilm-forming bacterial pathogens. Various studies have demonstrated that the AgNPs cause oxidative stress, protein dysfunction, membrane disruption, and DNA damage in bacteria, ultimately leading to bacterial death. AgNPs have also been found to alter the adhesion of bacterial cells to prevent biofilm formation. The benefits of using AgNPs in medicine are, to some extent, counter-weighted by their toxic effect on humans and the environment. In this review, we have compiled recent studies demonstrating the antibacterial activity of AgNPs, and we are discussing the known mechanisms of action of AgNPs against bacterial pathogens. Ongoing clinical trials involving AgNPs are briefly presented. A particular focus is placed on the mechanism of interaction of AgNPs with bacterial biofilms, which are a significant pathogenicity determinant. A brief overview of the use of AgNPs in other medical applications (e.g., diagnostics, promotion of wound healing) and the non-medical sectors is presented. Finally, current drawbacks and limitations of AgNPs use in medicine are discussed, and perspectives for the improved future use of functionalized AgNPs in medical applications are presented.

Silver-dendrimer nanocomposite as emerging therapeutics in anti-bacteria and beyond

To develop next-generation nanomedicine, theranostic nanotherapeutic strategies are increasingly being emphasized. In recent years, it is observed that the effective lifetime of anti-bacterial and anti-cancer agent is diminishing, which undermines the economic incentives necessary for clinical development and therapeutic applications. Thus, novel formulations ought to not only kill drug resistant strains and cancerous cells but also inhibit their formation. Recently, metallic nanoparticles [for example- silver (Ag) nanoparticles] have been widely investigated for their biomedical applications. The so-called applications necessitate the inclusion of these nanoparticles inside polymeric matrices (for example- dendrimer) leading to chemical functionalization of the metallic nanoparticles. Silver and silver nanoparticles' antibacterial activity has already been well established over years. Dendrimers due to their homogeneous highly branched structure and uniform composition are perfectly suitable for the inclusion of silver nanoparticles [Ag NPs]. Recently, the increasing trend in the development of Ag-dendrimer nanocomposites is attributed to the excellent antibacterial activity of Ag as well as dendrimer's unique properties like variable functional terminal ends and potential antibacterial effect necessarily. This review provides an informative overview regarding the numerous aspects of bactericidal and other biomedical applications of Ag-dendrimer nanocomposites, particularly emphasizing analysis of existing research and prospective worth to the pharmaceutical sector in future.

Chromophoric Dendrimer-Based Materials: An Overview of Holistic-Integrated Molecular Systems for Fluorescence Resonance Energy Transfer (FRET) Phenomenon

Dendrimers (from the Greek dendros → tree; meros → part) are macromolecules with well-defined three-dimensional and tree-like structures. Remarkably, this hyperbranched architecture is one of the most ubiquitous, prolific, and recognizable natural patterns observed in nature. The rational design and the synthesis of highly functionalized architectures have been motivated by the need to mimic synthetic and natural-light-induced energy processes. Dendrimers offer an attractive material scaffold to generate innovative, technological, and functional materials because they provide a high amount of peripherally functional groups and void nanoreservoirs. Therefore, dendrimers emerge as excellent candidates since they can play a highly relevant role as unimolecular reactors at the nanoscale, acting as versatile and sophisticated entities. In particular, they can play a key role in the properties of light-energy harvesting and non-radiative energy transfer, allowing them to function as a whole unit. Remarkably, it is possible to promote the occurrence of the FRET phenomenon to concentrate the absorbed energy in photoactive centers. Finally, we think an in-depth understanding of this mechanism allows for diverse and prolific technological applications, such as imaging, biomedical therapy, and the conversion and storage of light energy, among others.

Amine-terminated dendritic polymers as promising nanoplatform for diagnostic and therapeutic agents' modification: A review

It is often challenging to design diagnostic and therapeutic agents that fulfill all functional requirements. So, bulk and surface modifications as a common approach for biomedical applications have been suggested. There have been considerable research interests in using nanomaterials to the prementioned methods. Among all nanomaterials, dendritic materials with three-dimensional structures, host-guest properties, and nano-polymeric dimensions have received considerable attention. Amine-terminated dendritic structures including, polyamidoamine (PAMAM), polypropyleneimine (PPI), and polyethyleneimine (PEI), have been enormously utilized in bio-modification. This review briefly described the structure of these three common dendritic polymers and their use to modify diagnostic and therapeutic agents in six major applications, including drug delivery, gene delivery, biosensor, bioimaging, tissue engineering, and antimicrobial activity. The current review covers amine-terminated dendritic polymers toxicity challenging and improvement strategies as well.

Gene therapy in wound healing using nanotechnology

Wound healing is a complex and highly regulated process that is susceptible to a variety of failures leading to delayed wound healing or chronic wounds. This is becoming an increasingly global burden on the healthcare system. Treatment of wounds has evolved considerably to overcome barriers to wound healing especially within the field of regenerative medicine that focuses on the replacement of tissues or organs. Improved understanding of the pathophysiology of wound healing has enabled current advances in technology to allow better optimization of microenvironment within wounds. This approach may help tackle wounds that are difficult to treat and help reduce the global burden of the disease. This article provides an overview of the physiology in wound healing and the application of gene therapy using nanotechnology in the management of wounds.

Development of nanosilver doped carboxymethyl chitosan-polyamideamine alginate composite dressing for wound treatment

Nowadays, treatment to the infected wounds caused by bacterial even multi-resistant bacterial strains and subsequently complete skin regeneration remain a critical clinical challenge. Herein, a novel multi-functional platform (Alg/1.0Ag@CMC-PAMAM/PRP) was prepared as wound dressings by mixing platelet rich plasma (PRP) with the sodium alginate (Alg) based dressing containing nano silver (Ag)-doped carboxymethyl chitosan grafted polyamideamine (Ag@CMC-PAMAM) cationic polymers. The present dressings exhibited high swelling, suitable water vapor transmission rate (WVTR), and good mechanical properties and degradability, as well as sustained release of PRP. Besides, the component of Ag@CMC-PAMAM nanoparticles endow them with excellent antibacterial performance, while the incorporation of PRP promotes the effect of anti-inflammatory and angiogenesis by up-regulating relative activity factor expression of TGF-β1, CD31 and α-SMA and down-regulating the inflammatory-relative genes including TNF-α, IL-6 and IL-1β, all of which promote the closure of wound and produce a superior healing effect to the commercial Aquacel Ag group. This work indicates that the prepared Alg/1.0Ag@CMC-PAMAM/PRP wound dressing is a promising biomaterial with synergistic effect of antibacterial property and wound healing.

Plenty of Room at the Bottom: Nanotechnology as Solution to an Old Issue in Enhanced Oil Recovery

During the past half-century, the prefix “nano” attached to several words, such as “technology”, “motors”, “device”, and so on has denoted cutting-edge research fields and topics at the forefront of classical scientific disciplines. Possible application fields have been frequently evoked, even if real-life examples are still difficult to find. The present review analyzes how nanotechnology is utilized in enhanced oil recovery (EOR) processes so as to increase the efficiency of mature oilfields. Nanotechnology in EOR is classified into three categories: nanoparticles/nanofluids, nanoemulsions, and nanocatalysts. The advantages at the nanoscale are also described and discussed, including an overview of manufacturing methods as well as the concerns about their possible environmental impacts. Clearly, nanotechnology has the potential to boost EOR techniques, although there are still many questions and drawbacks to be tackled.

Hyperbranched Polyamidoamine Surfactants: Synthesis, Characterization and Evaluation as Biocides

Different generations of cationic hyperbranched quaternary ammonium polyamidoamine dendrimers (PAMAM) with methyl ester end group (G-0.5, G 0.5, G1.5 and G 2.5) were synthesized. Preparation of these dendrimers was carried out via alternative steps of an aza Michael addition reaction (of piperazine as core center molecule) and amidation reaction by ethylene diamine. Each aza Michael addition step was followed by a quaternization step using alkyl bromide with different chain length (4, 8 or 12) carbon atoms. The chemical structures of the prepared dendrimers were confirmed using FTIR, 1H-NMR spectra and elemental analysis for two generations as representative compounds. Also their surface activity has been studied and their surface parameters including surface and interfacial tension, emulsification power, critical micelle concentration, effectiveness, efficiency, maximum surface excess and minimum surface area were determined. The prepared quaternized dendrimers were tested as antimicrobial agents against different strains of bacteria, yeast and fungi. The results showed a significant antimicrobial efficacy of the synthesized surfactants.

Biomedical Applications of Silver Nanoparticles: An Up-to-Date Overview

During the past few years, silver nanoparticles (AgNPs) became one of the most investigated and explored nanotechnology-derived nanostructures, given the fact that nanosilver-based materials proved to have interesting, challenging, and promising characteristics suitable for various biomedical applications. Among modern biomedical potential of AgNPs, tremendous interest is oriented toward the therapeutically enhanced personalized healthcare practice. AgNPs proved to have genuine features and impressive potential for the development of novel antimicrobial agents, drug-delivery formulations, detection and diagnosis platforms, biomaterial and medical device coatings, tissue restoration and regeneration materials, complex healthcare condition strategies, and performance-enhanced therapeutic alternatives. Given the impressive biomedical-related potential applications of AgNPs, impressive efforts were undertaken on understanding the intricate mechanisms of their biological interactions and possible toxic effects. Within this review, we focused on the latest data regarding the biomedical use of AgNP-based nanostructures, including aspects related to their potential toxicity, unique physiochemical properties, and biofunctional behaviors, discussing herein the intrinsic anti-inflammatory, antibacterial, antiviral, and antifungal activities of silver-based nanostructures.

Synthesis of the erythromycin-conjugated nanodendrimer and its antibacterial activity

The development and spread of bacterial resistance to antimicrobial drugs necessitates the need to search for novel and effective antimicrobial agents. In the last few decades, innovative nanomaterials are attracting increasing attention and, among them, dendrimers have shown wide application in the various fields. In the current study, the two generations of an anionic linear- spherical nanodendrimer G1 and G2 were synthetized and compound G2 of nanodendrimer conjugated with erythromycin. The structures of the nanodendrimers were characterized by FTIR spectroscopy, zetasizer, and scanning electron microscopy (SEM). The antibacterial activity of the erythromycin-conjugated nanodendrimer and erythromycin alone were evaluated by the microdilution method against Staphylococcus aureus, S. epidermidis, S. saprophyticus, and Pseudomonas aeruginosa. The size of first and second generation of nanodendrimer, and the erythromycin-conjugated nanodendrimer was 75, 95, and 65.6 nm, respectively. The drug loading percentage of the nanodendrimer conjugates was obtained to be in 35.2%. In our study, the erythromycin-conjugated nanodendrimer showed significantly more bacteriostatic and bactericidal activities against all four studied bacteria than erythromycin alone. Our study's results highlight that the erythromycin-conjugated nanodendrimer is a highly effective agent against Gram positive and negative bacteria. The antibacterial properties of erythromycin combined with the targeting potential of the nanodendrimer can lead to sustained intracellular delivery of therapeutic agent.

A Nanocomposite Hydrogel with Potent and Broad-Spectrum Antibacterial Activity

Local bacterial infection is a challenging task and still remains a serious threat to human health in clinics. Systemic administration of antibiotics has only short-term antibacterial activity and usually causes adverse effects and bacterial resistance. A bioadhesive hydrogel with broad-spectrum and on-demand antibiotic activity is highly desirable. Here, we designed a pH-responsive nanocomposite hydrogel via a Schiff base linkage between oxidized polysaccharides and cationic dendrimers encapsulated with silver nanoparticles. The antibacterial components, both the cationic dendrimers and silver species, could be released in response to the acidity generated by growing bacteria. The released cationic polymer and silver exhibited a synergistic effect in antibacterial activity, and thus, the nanocomposite hydrogel showed potent antibacterial activity against both Gram-negative ( Escherichia coli and Pseudomonas aeruginosa) and Gram-positive bacteria ( Staphylococcus epidermidis and Staphylococcus aureus). The gel showed superior in vivo antibacterial efficacy against S. aureus infection compared with a commercial silver hydrogel at the same silver concentration. In addition, no obvious hemolytic toxicity, cytotoxicity, and tissue and biochemical toxicity were observed for the antibacterial hydrogel after incubation with cells or implantation. This study provides a facile and promising strategy to develop smart hydrogels to treat local bacterial infections.

Antibacterial Efficacy of Silver Nanoparticles on Endometritis Caused by Prevotella melaninogenica and Arcanobacterum pyogenes in Dairy Cattle

Bovine postpartum diseases remain one of the most significant and highly prevalent illnesses with negative effects on the productivity, survival, and welfare of dairy cows. Antibiotics are generally considered beneficial in the treatment of endometritis; however, frequent usage of each antibiotic drug is reason for the emergence of multidrug resistance (MDR) of the pathogenic microorganisms, representing a major impediment for the successful diagnosis and management of infectious diseases in both humans and animals. We synthesized silver nanoparticles (AgNPs) with an average size of 10 nm using the novel biomolecule apigenin as a reducing and stabilizing agent, and evaluated the efficacy of the AgNPs on the MDR pathogenic bacteria Prevotella melaninogenica and Arcanobacterium pyogenes isolated from uterine secretion samples. AgNPs inhibited cell viability and biofilm formation in a dose- and time-dependent manner. Moreover, the metabolic toxicity of the AgNPs was assessed through various cellular assays. The major toxic effect of cell death was caused by an increase in oxidative stress, as evidenced by the increased generation of reactive oxygen species (ROS), malondialdehyde, protein carbonyl content, and nitric oxide. The formation of ROS is considered to be the primary mechanism of bacterial death. Therefore, the biomolecule-mediated synthesis of AgNPs shows potential as an alternative antimicrobial therapy for bovine metritis and endometritis.

Dendrimer as a multifunctional capping agent for metal nanoparticles for use in bioimaging, drug delivery and sensor applications

Various strategies (single & multi-pot) to synthesize dendrimer-coated metal nanoparticles and their exploration in various biomedical applications.

Synthesis, photophysical, antibacterial and molecular docking studies on aromatic ring core-containing rhodamine B decorated triazole bridged dendrimers

Rhodamine B decorated dendrimers 1–6 were synthesized by a convergent approach using click chemistry. The zeroth generation dendrimer 1 (G0) and the first generation dendrimer 4 (G1) showed better antibacterial activity than the other dendrimers.

Determination of nitrite ions in environment analysis with a paper-based microfluidic device

A new microfluidic paper-based analytical device, a (Ag-μPAD)-based chemiresistor composed of silver ink, has been developed for the selective, sensitive, and quantitative determination of nitrite ions in environmental analysis.

Dendrimer conjugated estramustine nanocrystalline 'Dendot': An effective inhibitor of DMBA-TPA induced papilloma formation in mouse

Clinically approved anticancer drug estramustine mediates its function by impairing microtubule polymerization. However, the low aqueous solubility and high toxicity limit its anticancer activity via the oral route. Previously, efforts have been made to develop an enhanced water soluble form of estramustine as estramustine phosphate (EM) but acidic gastrointestinal pH breaks the phosphate derivative via oral administration. As an alternative approach, we have made an effort to enhance solubility and minimize toxicity in vivo by conjugating EM to a poly(amidoamine) (PAMAM) dendrimer, which generated the sustained release of dendrimer conjugate (DEM). To the best of our knowledge, for the first time, we report the direct proof of the nano-crystalline 'DenDot' of DEM on TEM image. The toxicity study showed that both EM and DEM were nontoxic up to 20mg/kg. A comparative anti-papilloma study was also performed with EM and dendrimer conjugates (DEM) using a two-stage mouse skin carcinogenesis model. We found that DEM was more effective in inhibiting skin tumor formation than EM. Histopathology and immunohistochemistry studies further indicated that DEM treatment increased cell apoptosis, and reduced epithelial hyperplasia, cell proliferation and inflammation in skin tissues of mice. In addition, the synthetic DEM conjugate inhibited skin tumor progression more effectively than EM.

In vitro antibacterial activity of poly (amidoamine)-G7 dendrimer

BACKGROUND

Nano-scale dendrimers are synthetic macromolecules that frequently used in medical and health field. Traditional anibiotics are induce bacterial resistence so there is an urgent need for novel antibacterial drug invention. In the present study seventh generation poly (amidoamine) (PAMAM-G7) dendrimer was synthesized and its antibacterial activities were evaluated against representative Gram- negative and Gram-positive bacteria.

METHODS

PAMAM-G7 was synthesized with divergent growth method. The structural and surface of PAMAM-G7 were investigated by transmission electron microscopy, scanning electron microscope and fourier transform infrared. Pseudomonas. aeruginosa (n = 15), E. coli (n = 15), Acinetobacter baumanni (n = 15), Shigella dysenteriae (n = 15), Klebsiella pneumoniae (n = 10), Proteus mirabilis (n = 15), Staphylococcus aureus (n = 15) and Bacillus subtilis (n = 10) have been used for antibacterial activity assay. Additionally, representative standard strains for each bacterium were included. Minimum Inhibitory Concentration (MIC) was determined using microdilution method. Subsequently, Minimum Bactericidal Concentration (MBC) was determined by sub-culturing each of the no growth wells onto Mueller Hinton agar medium. The cytotoxicity of PAMAM-G7 dendrimer were evaluated in HCT116 and NIH 3 T3 cells by MTT assay.

RESULTS

The average size of each particle was approximately 20 nm. PAMAM-G7 was potentially to inhibit both Gram positive and gram negative growth. The MIC50 and MIC90 values were determined to be 2-4 μg/ml and 4-8 μg/ml, respectively. The MBC50 and MBC90 values were found to be 64-256 μg/ml and 128-256 μg/ml, respectively. The cytotoxity effect of dendrimer on HCT116 and NIH 3 T3 cells is dependent upon exposure time to and concentration of dendrimers. The most reduction (44.63 and 43%) in cell viability for HCT116 and NIH 3 T3 cells was observed at the highest concentration, 0.85 μM after 72 h treatmentm, respectively.

CONCLUSIONS

This study we conclude that PAMAM-G7 dendrimer could be a potential candidate as a novel antibacterial agent.

Implementation of Nanoparticles in Cancer Therapy

Cancer is a wide group of diseases and generally characterized by uncontrolled proliferation of cells whose metabolic activities are disrupted. Conventionally, chemotherapy, radiotherapy, and surgery are used in the treatment of cancer. However, in theory, even a single cancer cell may trigger recurrence. Therefore, these treatments cannot provide high survival rate for deadly types. Identification of alternative methods in treatment of cancers is inevitable because of adverse effects of conventional methods. In the last few decades, nanotechnology developed by scientists working in different disciplines—physics, chemistry, and biology—offers great opportunities. It is providing elimination of both circulating tumor cells and solid cancer cells by targeting cancer cells. In this chapter, inadequate parts of conventional treatment methods, nanoparticle types used in new treatment methods of cancer, and targeting methods of nanoparticles are summarized; furthermore, recommendations of future are provided.

Capping Agent-Dependent Toxicity and Antimicrobial Activity of Silver Nanoparticles: An In Vitro Study. Concerns about Potential Application in Dental Practice

Objectives: In dentistry, silver nanoparticles (AgNPs) have drawn particular attention because of their wide antimicrobial activity spectrum. However, controversial information on AgNPs toxicity limited their use in oral infections. Therefore, the aim of the present study was to evaluate the antibacterial activities against a panel of oral pathogenic bacteria and bacterial biofilms together with potential cytotoxic effects on human gingival fibroblasts of 10 nm AgNPs: non-functionalized - uncapped (AgNPs-UC) as well as surface-functionalized with capping agent: lipoic acid (AgNPs-LA), polyethylene glycol (AgNPs-PEG) or tannic acid (AgNPs-TA) using silver nitrate (AgNO3) as control. Methods: The interaction of AgNPs with human gingival fibroblast cells (HGF-1) was evaluated using the mitochondrial metabolic potential assay (MTT). Antimicrobial activity of AgNPs was tested against anaerobic Gram-positive and Gram-negative bacteria isolated from patients with oral cavity and respiratory tract infections, and selected aerobic Staphylococci strains. Minimal inhibitory concentration (MIC) values were determined by the agar dilution method for anaerobic bacteria or broth microdilution method for reference Staphylococci strains and Streptococcus mutans. These strains were also used for antibiofilm activity of AgNPs. Results: The highest antimicrobial activities at nontoxic concentrations were observed for the uncapped AgNPs and the AgNPs capped with LA. It was found that AgNPs-LA and AgNPs-PEG demonstrated lower cytotoxicity as compared with the AgNPs-TA or AgNPs-UC in the gingival fibroblast model. All of the tested nanoparticles proved less toxic and demonstrated wider spectrum of antimicrobial activities than AgNO3 solution. Additionally, AgNPs-LA eradicated Staphylococcus epidermidis and Streptococcus mutans 1-day biofilm at concentration nontoxic to oral cells. Conclusions: Our results proved that a capping agent had significant influence on the antibacterial, antibiofilm activity and cytotoxicity of AgNPs. Clinical significance: This study highlighted potential usefulness of AgNPs against oral anaerobic Gram-positive and Gram-negative bacterial infections and aerobic Staphylococci strains provided that pharmacological activity and risk assessment are carefully performed.

Synthesis of TiO2 nanoparticles in the PAMAM hydrogen network template

Intramolecular nanocavities in polyamidoamine (PAMAM) are usually used as a good template to synthesize nanoparticles. In this paper, TiO2 nanoparticles were prepared successfully by the interspaces of the hydrogen network between PAMAM. The possible mechanism was that PAMAM could form the steady microspheres with many interspaces in ammonia aqueous solution at pH=10. The interspaces of the hydrogen network could act as the template for preparing TiO2 nanoparticles. The results were proved by transmission electron microscopy (TEM) and X-ray diffraction (XRD).

Nanoformulation and encapsulation approaches for poorly water-soluble drug nanoparticles

During the last few decades the nanomedicine sector has emerged as a feasible and effective solution to the problems faced by the high percentage of poorly water-soluble drugs. Decreasing the size of such drug compounds to the nanoscale can significantly change their physical properties, which lays the foundation for the use of nanomedicine for pharmaceutical applications. Various techniques have been developed to produce poorly water-soluble drug nanoparticles, mainly to address the poor water-soluble issues but also for the efficient and targeted delivery of such drugs. These techniques can be generally categorized into top-down, bottom-up and encapsulation approaches. Among them, the top-down approaches have been the main choice for industrial preparation of drug nanoparticles while other methods are actively investigated by researchers. In this review, we aim to give a comprehensive overview and latest progress of the top-down, bottom-up, and encapsulation methods for the preparation of poorly water-soluble drug nanoparticles and how solvents and additives can be selected for these methods. In addition to the more industrially applied top-down approaches, the review is focused more on bottom-up and encapsulation methods, particularly covering supercritical fluid-related methods, cryogenic techniques, and encapsulation with dendrimers and responsive block copolymers. Some of the approved and mostly used nanodrug formulations on the market are also covered to demonstrate the applications of poorly water-soluble drug nanoparticles. This review is complete with perspectives on the development and challenges of fabrication techniques for more effective nanomedicine.

The Effect of Cationic Polyamidoamine Dendrimers on Physicochemical Characteristics of Hydrogels with Erythromycin

Polyamidoamine dendrimers (PAMAM) represent a new class of hyperbranched, monodisperse, three-dimensional polymers with unique properties, which make them very promising carriers of antimicrobial agents. The present study aimed to evaluate the influence of PAMAM-NH₂ dendrimers generation two (G2) or three (G3) on physicochemical characteristics and structure of hydrogels with a model antibacterial lipophilic drug-erythromycin-commonly used in topical applications. From the obtained rheograms, it can be concluded that tested hydrogels were non-Newtonian thixotropic systems with shear-thinning behaviour. The dissolution tests revealed that erythromycin was definitely faster released from formulations containing PAMAM-NH₂ in concentration and generation dependent manner. However, the addition of PAMAM-NH₂ to hydrogels evoked only slight improvement of their antibacterial activity. It was also shown that the structure of hydrogels changed in the presence of PAMAM-NH₂ becoming less compact, diversified and more porous. Designed hydrogels with PAMAM-NH₂ G2 or G3 were stable stored up to three months at 40 ± 2 °C and 75% ± 5% RH.

Antimicrobial polymeric materials with quaternary ammonium and phosphonium salts

Polymeric materials containing quaternary ammonium and/or phosphonium salts have been extensively studied and applied to a variety of antimicrobial-relevant areas. With various architectures, polymeric quaternary ammonium/phosphonium salts were prepared using different approaches, exhibiting different antimicrobial activities and potential applications. This review focuses on the state of the art of antimicrobial polymers with quaternary ammonium/phosphonium salts. In particular, it discusses the structure and synthesis method, mechanisms of antimicrobial action, and the comparison of antimicrobial performance between these two kinds of polymers.

Nanoengineered drug delivery systems for enhancing antibiotic therapy

Formulation scientists are recognizing nanoengineered drug delivery systems as an effective strategy to overcome limitations associated with antibiotic drug therapy. Antibiotics encapsulated into nanodelivery systems will contribute to improved management of patients with various infectious diseases and to overcoming the serious global burden of antibiotic resistance. An extensive review of several antibiotic-loaded nanocarriers that have been formulated to target drugs to infectious sites, achieve controlled drug release profiles, and address formulation challenges, such as low-drug entrapment efficiencies, poor solubility and stability is presented in this paper. The physicochemical properties and the in vitro/in vivo performances of various antibiotic-loaded delivery systems, such as polymeric nanoparticles, micelles, dendrimers, liposomes, solid lipid nanoparticles, lipid-polymer hybrid nanoparticles, nanohybirds, nanofibers/scaffolds, nanosheets, nanoplexes, and nanotubes/horn/rods and nanoemulsions, are highlighted and evaluated. Future studies that will be essential to optimize formulation and commercialization of these antibiotic-loaded nanosystems are also identified. The review presented emphasizes the significant formulation progress achieved and potential that novel nanoengineered antibiotic drug delivery systems have for enhancing the treatment of patients with a range of infections.

Differences in physicochemical properties to consider in the design, evaluation and choice between microparticles and nanoparticles for drug delivery

INTRODUCTION

The increase in the development of novel nanoparticle drug delivery systems makes the choice between micro- and nanoscale drug delivery systems ubiquitous. Changes in physical and chemical properties between micro- to nanosized particles give them different properties that influence their physiological, anatomical and clinical behavior and therefore potential application.

AREAS COVERED

This review focuses on the effect changes in the surface-to-volume ratio have on the thermal properties, solubility, dissolution and crystallization of micro- versus nanosized drug delivery systems. With these changes in the physicochemical properties in mind, the review covers computational and biophysical approaches to the design and evaluation of micro- and nanodelivery systems. The emphasis of the review is on the effect these properties have on clinical performance in terms of drug release, tissue retention, biodistribution, efficacy, toxicity and therefore choice of delivery system.

EXPERT OPINION

Ultimately, the choice between micro- and nanometer-sized delivery systems is not straightforward. However, if the fundamental differences in physical and chemical properties are considered, it can be much easier to make a rational choice of the appropriate drug delivery system size.

Prevention of biofilm formation by methacrylate-based copolymer films loaded with rifampin, clarithromycin, doxycycline alone or in combination

PURPOSE

This study reports the incorporation of the antibiotics rifampin, doxycycline and clarithromycin in poly(styrene-co-methyl methacrylate films and their effect on biofilm prevention.

BACKGROUND

Invasive procedures in patients such as surgical device, or intravenous or urinary catheter implantation, often results in complicated hospital-acquired nosocomial infections. Biofilm formation is essential to establish these infections on these devices and novel antibiotic delivery approaches are needed for more effective management.

METHODS

The films were evaluated in vitro for drug release and for their ability to prevent biofilm formation by methicillin susceptible and methicillin resistant Staphylococcus aureus. Surface tension components, obtained from contact angle measurements, and the morphology of the films evaluated by scanning electron microscopy were also investigated.

RESULTS

In this study, antibiotic-loaded methacrylic copolymer films that effectively released rifampin, clarithromycin and doxycycline for up to 21 days prevented biofilm formation when tested in an in vitro bioreactor model. These drug loaded copolymer films provided the advantage by coating materials with a novel surface that was unsuitable for resettling of biofilms once the antibiotic was dissolved from the polymer surface. A combination of rifampin and clarithromycin released from the polymer film provided >99.9% kill of an MRSA inoculate for up to 72 h.

CONCLUSION

Results showed that combining multiple drugs in copolymer films with unique surface properties, initial hydrophilicity and increase in roughness, can be an effective way to prevent biofilm formation.

Antibacterial polymeric nanostructures for biomedical applications

A topical review on recent advances in the research and applications of antimicrobial polymeric nanostructures, such as silver-decorated polymeric nanostructures, and polymeric micelles and vesicles based on antimicrobial polymers and antimicrobial peptides.

Silver- and sulfadiazine-loaded nanostructured silica materials as potential replacement of silver sulfadiazine

Sulfadiazine-loaded silver nanoporous silica carriers have similar antibacterial properties as silver sulfadiazine.

Dendrimers - from organic synthesis to pharmaceutical applications: an update

Dendrimers are a relatively new class of monodisperse polymers, which have tree-like spherical structures with well-defined sizes and shapes. Their unique structure has a significant impact on their physical and chemical properties. Research on dendrimers is of significant interest to scientists from all areas and their utility in various scientific fields, including pharmaceuticals, is expanding. The present review is comprehensive and covers different aspects of dendrimers viz. (1) synthesis, (2) properties and (3) pharmaceutical applications. The emphasis is on their applications as well as the current ongoing research status for drug targeting.

The effect of PAMAM dendrimers on the antibacterial activity of antibiotics with different water solubility

Erythromycin (EM) and tobramycin (TOB) are well-known and widely used antibiotics, belonging to different therapeutic groups: macrolide and aminoglycoside, respectively. Moreover, they possess different solubility: EM is slightly soluble and TOB is freely soluble in water. It was previously demonstrated that PAMAM dendrimers enhanced the pharmacological activity of antifungal drugs by increasing their solubility. Therefore, it appears interesting to investigate the effect of PAMAM-NH2 and PAMAM-OH dendrimers generation 2 (G2) and generation 3 (G3) on the antibacterial activity of antibiotics with different water solubility. In this study it was shown that the aqueous solubility of EM was significantly increased by PAMAM dendrimers (PAMAM-NH2 and PAMAM-OH caused about 8- and 7- fold solubility increases, respectively). However, it was indicated that despite the increase in the solubility, there was only slight influence on the antibacterial activity of EM (2- and 4-fold decreases in the MBC values of EM in the presence of PAMAM-OH G3 and PAMAM-NH2 G2 or G3 for strains of Staphylococcus aureus were noted, respectively). It was also found that there was no influence of PAMAM on the antibacterial activity of hydrophilic TOB.

Dendrimers in layer-by-layer assemblies: synthesis and applications

We review the synthesis of dendrimer-containing layer-by-layer (LbL) assemblies and their applications, including biosensing, controlled drug release, and bio-imaging. Dendrimers can be built into LbL films and microcapsules by alternating deposition of dendrimers and counter polymers on the surface of flat substrates and colloidal microparticles through electrostatic bonding, hydrogen bonding, covalent bonding, and biological affinity. Dendrimer-containing LbL assemblies have been used to construct biosensors, in which electron transfer mediators and metal nanoparticles are often coupled with dendrimers. Enzymes have been successfully immobilized on the surface of electrochemical and optical transducers by forming enzyme/dendrimer LbL multilayers. In this way, high-performance enzyme sensors are fabricated. In addition, dendrimer LbL films and microcapsules are useful for constructing drug delivery systems because dendrimers bind drugs to form inclusion complexes or the dendrimer surface is covalently modified with drugs. Magnetic resonance imaging of cancer cells by iron oxide nanoparticles coated with dendrimer LbL film is also discussed.

Silver sulfadiazine nanosystems for burn therapy

The objective of the present study was to formulate stable silver sulfadiazine (SSD) nanosuspensions and nanogels suitable for topical delivery with a view to increase bactericidal activity in burn therapy. SSD nanosuspensions were formulated using the microprecipitation-high-pressure homogenization technique. An optimized microsuspension of 0.5% SSD formulated with 6% Cremophor EL and 4% Lauroglycol 90 was subjected to 30 cycles of 1,000-bar pressure to give a nanosuspension with an average particle size of 367.85 nm. Transmission electron microscopy studies revealed that ovoid- to rectangular-shaped SSD particles were present as clusters. It was evident through X-ray diffraction studies that SSD was present in amorphous state both in microprecipitate and in nanosuspension. SSD (0.5%) nanogels were prepared using 1% Carbopol 974 P for topical delivery of nanosized SSD. In vitro release studies demonstrated that SSD release was faster from solutions and nanosuspensions compared to gel formulation owing to the influence of the gel matrix on SSD release. The bacterial inhibitory efficiency of SSD nanosuspension was as good as that of SSD solution against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. In vivo studies revealed that a nanogel containing 0.5% SSD was more effective in wound healing compared to 0.5% and 1% marketed cream.

Cationic polymers and their therapeutic potential

The last decade has witnessed enormous research focused on cationic polymers. Cationic polymers are the subject of intense research as non-viral gene delivery systems, due to their flexible properties, facile synthesis, robustness and proven gene delivery efficiency. Here, we review the most recent scientific advances in cationic polymers and their derivatives not only for gene delivery purposes but also for various alternative therapeutic applications. An overview of the synthesis and preparation of cationic polymers is provided along with their inherent bioactive and intrinsic therapeutic potential. In addition, cationic polymer based biomedical materials are covered. Major progress in the fields of drug and gene delivery as well as tissue engineering applications is summarized in the present review.