Advancing Antibiotic-Resistant Microbe Combat: Nanocarrier-Based Systems in Combination Therapy Targeting Quorum Sensing

The increase in antibiotic-resistant bacteria presents a significant risk to worldwide public health, emphasizing the necessity of novel approaches to address infections. Quorum sensing, an essential method of communication among bacteria, controls activities like the formation of biofilms, the production of virulence factors, and the synthesis of secondary metabolites according to the number of individuals in the population. Quorum quenching, which interferes with these processes, emerges as a vital approach to diminish bacterial virulence and prevent biofilm formation. Nanocarriers, characterized by their small size, high surface-area-to-volume ratio, and modifiable surface chemistry, offer a versatile platform for the disruption of bacterial communication by targeting various stages within the quorum sensing pathway. These features allow nanocarriers to infiltrate biofilms, disrupt cell membranes, and inhibit bacterial proliferation, presenting a promising alternative to traditional antibiotics. Integrating nanocarrier-based systems into combination therapies provides a multi-pronged approach to infection control, enhancing both the efficacy and specificity of treatment regimens. Nonetheless, challenges related to the stability, safety, and clinical effectiveness of nanomaterial-based antimicrobial treatments remain. Continued research and development are essential to overcoming these obstacles and fully harnessing the potential of nano-antimicrobial therapies. This review emphasizes the importance of quorum sensing in bacterial behavior and highlights the transformative potential of nanotechnology in advancing antimicrobial treatments, offering innovative solutions to combat antibiotic-resistant pathogens.

Targeted nanotherapeutics for the treatment of Helicobacter pylori infection

Helicobacter pylori infection is involved in gastric diseases such as peptic ulcer and adenocarcinoma. Approved antibiotherapies still fail in 10 to 40% of the infected patients and, in this scenario, targeted nanotherapeutics emerged as powerful allies for H. pylori eradication. Nano/microparticles conjugated with H. pylori binding molecules were developed to eliminate H. pylori by either (i) blocking essential mechanisms of infection, such as adhesion to gastric mucosa or (ii) binding and killing H. pylori through the release of drugs within the bacteria or at the site of infection. Glycan antigens (as Lewis B and sialyl-Lewis X), pectins, lectins, phosphatidylethanolamine and epithelial cell membranes were conjugated with nano/microparticles to successfully block H. pylori adhesion. Urea-coated nanoparticles were used to improve drug delivery inside bacteria through H. pylori UreI channel. Moreover, nanoparticles coated with antibodies against H. pylori and loaded with sono/photosensitizers, were promising for their application as targeted sono/photodynamic therapies. Further, non-specific H. pylori nano/microparticles, but only active in the acidic gastric environment, coated with binders to bacterial membrane, extracellular polymeric substances or to high temperature requirement A protease, were evaluated. In this review, an overview of the existing nanotherapeutics targeting H. pylori will be given and their rational, potential to counteract infection, as well as level of development will be presented and discussed.

Green Extracts with Metal-based Nanoparticles for Treating Inflammatory Diseases: A Review

Globally, high death rates and poor quality of life are caused mainly by inflammatory diseases. Corticosteroids, which may have systemic side effects and would enhance the risk of infection, are the common forms of therapy. The field of nanomedicine has created composite nanoparticles that carry a pharmacological carrier and target ligands for distribution to sites of inflammation with less systemic toxicity. However, their relatively large size often causes systemic clearance. An interesting approach is metal-based nanoparticles that naturally reduce inflammation. They are made not only to be small enough to pass through biological barriers but also to allow label-free monitoring of their interactions with cells. The following literature review discusses the mechanistic analysis of the anti-inflammatory properties of several metal-based nanoparticles, including gold, silver, titanium dioxide, selenium, and zinc oxide. Current research focuses on the mechanisms by which nanoparticles infiltrate cells and the anti-inflammatory techniques using herbal extracts-based nanoparticles. Additionally, it provides a brief overview of the literature on many environmentally friendly sources employed in nanoparticle production and the mechanisms of action of various nanoparticles.

Plant-based green synthesis of nanoparticles as an effective and safe treatment for gastric ulcer

Gastric ulcer is a chronic disease that affects about 10% of the world's population. This disease is caused by factors such as stress, smoking, alcohol consumption, nonsteroidal anti-inflammatory drugs (NSAIDs), Helicobacter pylori infection, and genetic factors. Herbal medicines such as plant extracts are new sources of drugs with promising results in treating gastric ulcers. Nanotechnology and nanomedicine have been able to reach this objective to some extent. Green synthesis is an alternative method adapted for chemical and physical methods. In the last few years, fungi, bacteria, viruses, algae, and plants have been used to produce metallic nanoparticles. Since nanoparticles synthesized by the green method can be effective in anticancer, antidiabetic, antiulcer, anti-inflammatory, and antioxidant treatments, the aim of this review was to study the effect of metal nanoparticles and metal oxides produced by the green method on the treatment of gastric ulcers. For this purpose, an electronic search of published research and review articles in PubMed, Scopus, Science Direct, Cochrane databases, and Google Scholar was conducted using a combination of keywords of "gastric ulcers and nanoparticles", "gastric ulcers and Green synthesis" and "stomach ulcers and nanoparticles". After a full review of published articles and their references, 120 articles were identified for further detailed review. The articles selected were between 2000 and March 2023, and 2 articles published in 1972 and 1997 were utilized. The results of this study have shown that polymeric, metal, and metal oxide nanoparticles synthesized from plants can be effective in treating gastric ulcers, especially ulcers caused by H. pylori, ethanol, and NSAIDs.

Application of biomaterials in the eradication of Helicobacter pylori: A bibliometric analysis and overview

Helicobacter pylori is a prominent cause of gastritis, peptic ulcer, and gastric cancer. It is naturally colonized on the surface of the mucus layer and mucosal epithelial cells of the gastric sinus, surrounded not only by mucus layer with high viscosity that prevents the contact of drug molecules with bacteria but also by multitudinous gastric acid and pepsin, inactivating the antibacterial drug. With high-performance biocompatibility and biological specificity, biomaterials emerge as promising prospects closely associated with H. pylori eradication recently. Aiming to thoroughly summarize the progressing research in this field, we have screened 101 publications from the web of science database and then a bibliometric investigation was performed on the research trends of the application of biomaterials in eradicating H. pylori over the last decade utilizing VOSviewer and CiteSpace to establish the relationship between the publications, countries, institutions, authors, and most relevant topics. Keyword analysis illustrates biomaterials including nanoparticles (NPs), metallic materials, liposomes, and polymers are employed most frequently. Depending on their constituent materials and characterized structures, biomaterials exhibit diverse prospects in eradicating H. pylori regarding extending drug delivery time, avoiding drug inactivation, target response, and addressing drug resistance. Furthermore, we overviewed the challenges and forthcoming research perspective of high-performance biomaterials in H. pylori eradication based on recent studies.

Polymeric Nanoparticles for Delivery of Natural Bioactive Agents: Recent Advances and Challenges

In the last few decades, several natural bioactive agents have been widely utilized in the treatment and prevention of many diseases owing to their unique and versatile therapeutic effects, including antioxidant, anti-inflammatory, anticancer, and neuroprotective action. However, their poor aqueous solubility, poor bioavailability, low GIT stability, extensive metabolism as well as short duration of action are the most shortfalls hampering their biomedical/pharmaceutical applications. Different drug delivery platforms have developed in this regard, and a captivating tool of this has been the fabrication of nanocarriers. In particular, polymeric nanoparticles were reported to offer proficient delivery of various natural bioactive agents with good entrapment potential and stability, an efficiently controlled release, improved bioavailability, and fascinating therapeutic efficacy. In addition, surface decoration and polymer functionalization have opened the door to improving the characteristics of polymeric nanoparticles and alleviating the reported toxicity. Herein, a review of the state of knowledge on polymeric nanoparticles loaded with natural bioactive agents is presented. The review focuses on frequently used polymeric materials and their corresponding methods of fabrication, the needs of such systems for natural bioactive agents, polymeric nanoparticles loaded with natural bioactive agents in the literature, and the potential role of polymer functionalization, hybrid systems, and stimuli-responsive systems in overcoming most of the system drawbacks. This exploration may offer a thorough idea of viewing the polymeric nanoparticles as a potential candidate for the delivery of natural bioactive agents as well as the challenges and the combating tools used to overcome any hurdles.

Exopolysaccharide from Lactobacillus casei NA-2 attenuates Escherichia coli O157:H7 surface adhesion via modulation of membrane surface properties and adhesion-related gene expression

The natural compound, exopolysaccharide from Lactobacillus casei NA-2 (EPS-cn2), has been shown to inhibit biofilm formation by Escherichia coli O157:H7. Although bacterial adhesion to substrate surfaces is a primary, indispensable step in this process, the mechanisms by which EPS-cn2 can block E. coli O157:H7 adhesion to biotic or abiotic surfaces remain unclear. In this study, investigation of E. coli O157:H7 response to EPS-cn2 revealed that 1 mg/mL EPS-cn2 can decrease adherence to polystyrene and confluent Caco-2 cell surfaces to 49.0% (P＜0.0001) and 57.0% (P＜0.01) of that in untreated E. coli O157:H7, respectively. Moreover, EPS-cn2 significantly reduced outer membrane hydrophobicity by 49.0% and decreased the electronegativity of the membrane surface charge by as much as 1.57 mV (P＜0.05) compared to untreated cells. High throughput RNA sequencing indicated that genes responsible for adhesion through extracellular matrix secretion, such as poly-N-acetyl-glucosamine (PNAG) biosynthesis, locus of enterocyte effacement (LEE) proteins and outer membrane protein (OmpT) were all down-regulated in response to EPS-cn2, while chemotaxis and motility-related flagellar assembly genes were differentially up-regulated, suggesting that the EPS-cn2 may serve as an extracellular signal to attenuate adhesion-related gene expression and alter bacterial surface properties in E. coli O157:H7. These findings support the further development of EPS-cn2 for pathogenic biofilm management in clinical and industrial settings, and suggests the further targeting of adhesion-related genes to limit the persistence of this highly pathogenic strain in sensitive environments.

Biomaterials for Helicobacter pylori therapy: therapeutic potential and future perspectives

Helicobacter pylori (H. pylori) is the main cause of gastric adenocarcinoma. However, the traditional antibiotic treatment of H. pylori is limited due to increased antibiotic resistance and low efficacy; low drug delivery efficiency and difficulties in eradicating H. pylori that is present intracellularly or in biofilms cause further setbacks. Biomaterials that can protect drugs against stomach acid, target lesions, control drug release, destroy biofilms, and exhibit unique antibacterial mechanisms and excellent biocompatibility have emerged as attractive tools for H. pylori eradication, particularly for drug-resistant strains. Herein, we review the virulence mechanisms, current drug treatments, and antibiotic resistance of H. pylori strains. Furthermore, recent advances in the development of biomaterials, including nanoparticles (such as lipid-based nanoparticles, polymeric nanoparticles, and inorganic nanoparticles), microspheres, and hydrogels, for effective and precise therapy of H. pylori and different types of therapeutic mechanisms, as well as future perspectives, have also been summarized.

Chitosan-curcumin complexation to develop functionalized nanosystems with enhanced antimicrobial activity against hetero-resistant gastric pathogen

With the apparent stagnation in the antibiotic discovery and the propagation of multidrug resistance, Helicobacter pylori associated gastric infections are hard to eradicate. In pursuance of alternative medicines, in this study, covalent modification of chitosan (CS) polymer with curcumin (Cur) was accomplished. Proton Nuclear Magnetic Resonance and Fourier Transform Infrared spectroscopy elucidated the covalent interaction between Cur and CS with characteristic peak of imine functional group (C=N). Scanning Electron Microscopy provided visual proof for surface topology, while size and zeta potential values further affirmed the development of curcumin functionalized chitosan nanosystems (Cur-FCNS). The complexation efficiency of CS with Cur was found as 70 ± 3% at an optimal ratio of 5:1 for CS and Cur, respectively. Cur-FCNS developed with ionic gelation and ultrasonication method demonstrated synergistic anti-H. pylori activity in growth-kinetics and anti-biofilm assays, which was superior to free Cur and even chitosan nanosystems. Under simulated gastric conditions, Cur-FCNS revealed cumulative-release of only 16 ± 0.8% till 40 h, which indicated its improved stability to interact with H. pylori. In silico findings affirmed high binding affinity of Cur-FCNS with multiple bacterial virulence factors. Thus, our results affirmed the exceptional potential of Cur-FCNS as next-generation alternative-medicine to treat resistant H. pylori.

Grafting MSI-78A onto chitosan microspheres enhances its antimicrobial activity

MSI-78A (Pexiganan A) is one of the few antimicrobial peptides (AMPs) able to kill Helicobacter pylori, a pathogenic bacterium that colonizes the gastric mucosa of half of the world's population. Antibiotics fail in 20-40% of H. pylori-infected patients, reinforcing the need for alternative treatments. Herein, a bioengineered approach was developed. MSI-78A with a C-terminal cysteine was grafted onto chitosan microspheres (AMP-ChMic) by thiol-maleimide (Michael-addition) chemistry using a long heterobifunctional spacer (NHS-PEG₁₁₃-MAL). Microspheres with ∼4 µm diameter (near H. pylori length) and stable at low pH were produced by spray drying using a chitosan solution with an incomplete genipin crosslinking. A 3 × 10^-5 µg AMP/microsphere grafting was estimated/confirmed by UV/Vis and FTIR spectroscopies. AMP-ChMic were bactericidal against H. pylori J99 (highly pathogenic human strain) at lower concentrations than the free peptide (∼277 µg grafted MSI-78A-SH/mL vs 512 µg free MSI-78A-SH/mL), even after pre-incubation in simulated gastric conditions with pepsin. AMP-ChMic killed H. pylori by membrane destabilization and cytoplasm release in a ratio of ∼10 bacteria/microsphere. This can be attributed to H. pylori attraction to chitosan, facilitating the interaction of grafted AMP with bacterium membrane. Overall, it was demonstrated that the peptide-microsphere conjugation chemistry did not compromise the MSI-78A antimicrobial activity, instead it boosted its bactericidal performance against H. pylori. STATEMENT OF SIGNIFICANCE: Half of the world's population is infected with Helicobacter pylori, a gastric bacterium that is responsible for 90% of non-cardia gastric cancers. Therefore, H. pylori eradication is now advocated in all infected individuals. However, available antibiotic therapies fail in up to 40% patients. Antimicrobial peptides (AMPs) are appealing alternatives to antibiotics, but their high susceptibility in vivo limits their clinical translation. AMP immobilization onto biomaterials surface will overcome this problem. Herein, we demonstrate that immobilization of MSI-78A (one of the few AMPs with activity against H. pylori) onto chitosan microspheres (AMP-ChMic) enhances its anti-H. pylori activity even at acidic pH (gastric settings). These results highlight the strong potential of AMP-ChMic as an antibiotic alternative for H. pylori eradication.

Revisiting Therapeutic Strategies for H. pylori Treatment in the Context of Antibiotic Resistance: Focus on Alternative and Complementary Therapies

The prevalence of Helicobacter pylori infection remains significant worldwide and it depends on many factors: gender, age, socio-economic status, geographic area, diet, and lifestyle. All successful infectious diseases treatments use antibiotic-susceptibility testing, but this strategy is not currently practical for H. pylori and the usual cure rates of H. pylori are lower than other bacterial infections. Actually, there is no treatment that ensures complete eradication of this pathogen. In the context of an alarming increase in resistance to antibiotics (especially to clarithromycin and metronidazole), alternative and complementary options and strategies are taken into consideration. As the success of antibacterial therapy depends not only on the susceptibility to given drugs, but also on the specific doses, formulations, use of adjuvants, treatment duration, and reinfection rates, this review discusses the current therapies for H. pylori treatment along with their advantages and limitations. As an alternative option, this work offers an extensively referenced approach on natural medicines against H. pylori, including the significance of nanotechnology in developing new strategies for treatment of H. pylori infection.

Microfluidic-based synthesized carboxymethyl chitosan nanoparticles containing metformin for diabetes therapy: In vitro and in vivo assessments

This work was aimed to synthesize novel crosslinked carboxymethyl chitosan nanoparticles (CMCS NPs) containing metformin hydrochloride (MET) using microfluidics (MF) and evaluate their performance for diabetes therapy. The field emission-scanning electron microscopy (FE-SEM) images and dynamic light scattering (DLS) results showed that the NPs average size was 77 ± 19 nm with a narrow size distribution. They exhibited a high encapsulation efficiency (∼90 %) and the controlled drug release while crosslinking using CaCl₂. Eventually, the in vivo assessments dedicated an increased body weight up to 7.94 % and a decreased blood glucose level amount of 43.58 % for MF MET-loaded CMCS NPs with respect to the free drug in diabetic rats. Also, the results of histopathological studies revealed the size of the pancreatic islets to be 2.32 μm² and β cells intensity to be 64 cells per islet for the diabetic rats after treating with the MF-based sample. These data were close to those obtained for the healthy rats.

Recent Biomedical Approaches for Chitosan Based Materials as Drug Delivery Nanocarriers

In recent decades, drug delivery systems (DDSs) based on nanotechnology have been attracting substantial interest in the pharmaceutical field, especially those developed based on natural polymers such as chitosan, cellulose, starch, collagen, gelatin, alginate and elastin. Nanomaterials based on chitosan (CS) or chitosan derivatives are broadly investigated as promising nanocarriers due to their biodegradability, good biocompatibility, non-toxicity, low immunogenicity, great versatility and beneficial biological effects. CS, either alone or as composites, are suitable substrates in the fabrication of different types of products like hydrogels, membranes, beads, porous foams, nanoparticles, in-situ gel, microparticles, sponges and nanofibers/scaffolds. Currently, the CS based nanocarriers are intensely studied as controlled and targeted drug release systems for different drugs (anti-inflammatory, antibiotic, anticancer etc.) as well as for proteins/peptides, growth factors, vaccines, small DNA (DNAs) and short interfering RNA (siRNA). This review targets the latest biomedical approaches for CS based nanocarriers such as nanoparticles (NPs) nanofibers (NFs), nanogels (NGs) and chitosan coated liposomes (LPs) and their potential applications for medical and pharmaceutical fields. The advantages and challenges of reviewed CS based nanocarriers for different routes of administration (oral, transmucosal, pulmonary and transdermal) with reference to classical formulations are also emphasized.

Synthesis, characterization, anti-inflammatory and anti-Helicobacter pylori activities of novel benzophenone tetracarboxylimide benzoyl thiourea cross-linked chitosan hydrogels

Chitosan (Cs) was cross-linked with four various quantities of 4,4'-(5,5'‑carbonylbis(1,3-dioxoisoindoline-5,2-diyl))dibenzoyl isothiocyanate. Elemental analysis, FTIR and ¹H NMR spectroscopy assured that the amino groups of chitosan reacted with the isothiocyanate groups of the cross-linker producing four new hydrogels namely as BBTU-Cs-1, BBTU-Cs-2, BBTU-Cs-3, and BBTU-Cs-4 according to the increment of their cross-linking content, respectively. SEM showed their porous structures and XRD indicated their amorphous nature. Their swell ability increased with decreasing the medium pH value and with increasing cross-linking density. In comparison with the popular COX inhibitor Celecoxib, these hydrogels showed an inhibition activity towards COX enzymes with selective inhibition towards COX-2. Their inhibition activity could be arranged as follows: Celecoxib > BBTU-Cs-4 > BBTU-Cs-3 > BBTU-Cs-2 > BBTU-Cs-1. BBTU-CS-4 hydrogel exhibited a potent inhibition against COX-2 (IC₅₀ 0.42 μg/ml) compared with that observed for the standard Celecoxib (IC₅₀ 0.26 μg/ml). BBTU-Cs-4 is more potent against H. pylori compared to the other hydrogels. BBTU-Cs-4 at a concentration of 7.81 μg/ml is able to kill 100% of the H. pylori and exhibits a preferential ability to inhibit 89.35% of COX-2 than COX-1 (0%). These findings make BBTU-Cs-4 a promising anti-H. pylori and selective anti-inflammatory agent.

Nano-vehicles give new lease of life to existing antimicrobials

Antibiotic resistance has become one of the greatest challenges for modern medicine, and new approaches for the treatment of bacterial infections are urgently needed to avoid widespread vulnerability again to infections that have so far been easily treatable with existing drugs. Among the many approaches investigated to overcome this challenge is the use of engineered nanostructures for the precise and targeted delivery of existing antimicrobial agents in a fashion that will potentiate their effect. This idea leans on lessons learned from pioneering research in cancer, where the targeted delivery of anti-cancer drugs to mammalian cells has been a topic for some time. In particular, new research has demonstrated that nanomaterials can be functionalised with active antimicrobials and, in some cases, with targeting molecules that potentiate the efficiency of the antimicrobials. In this mini-review, we summarise results that demonstrate the potential for nanoparticles, dendrimers and DNA nanostructures for use in antimicrobial delivery. We consider material aspects of the delivery vehicles and ways in which they can be functionalised with antibiotics and antimicrobial peptides, and we review evidence for their efficacy to kill bacteria both in vitro and in vivo. We also discuss the advantages and limitations of these materials and highlight the benefits of DNA nanostructures specifically for their versatile potential in the present context.

Applications of chitosan and chitosan based metallic nanoparticles in agrosciences-A review

The second most abundant biological macromolecule, next to cellulose is Chitosan. It is a versatile naturally occurring hydrophilic polysaccharide, derived as a deacetylated form of chitin. Due to its biocompatibility, biodegradability and antimicrobial activity, it has become a significant area of research towards drug delivery system, plant growth promotion, anti-pathogenic potentiality, seed priming and in plant defense mechanism. Various synthetic strategies have been established in recent years that couples different metals with chitosan nanoparticles. Metals like silver, copper, zinc, iron and nickel are highly compatible to form chitosan metallic nanoparticles and are proved to be non-toxic to the agricultural plant system. This review highlights the mode of action of nanochitosan on Gram-positive and Gram-negative bacteria in a distinguished manner as well as its action on fungi. A prime focus has been given on the skeletal framework of the metallic nanochitosan particles. Our study also projects the antimicrobial mechanism of chitosan based on its physiochemical properties, environmental factors and the type of organism on which it acts. Moreover, the mechanism for stimulation of plant immunity by metallic nanochitosan has also been reviewed. Our study relies on the conclusion that chitosan metallic nanoparticles showed enhanced anti-pathogenic and plant growth promoting activity in comparison to bulk chitosan.

Orally administrated chitosan microspheres bind Helicobacter pylori and decrease gastric infection in mice

Persistent Helicobacter pylori (H. pylori) infection is related to 90% of gastric cancers. With bacterial resistance rising and treatment inefficiency affecting 15% of the patients, alternative treatments urge. Chitosan microspheres (ChMics) have been proposed as an H. pylori-binding system. This work evaluates ChMics biocompatibility, mucopenetration and capacity to treat H. pylori infection in mice after oral administration. ChMics of different size (XL, ∼120 µm and XS, ∼40 µm) and degree of acetylation (6% and 16%) were developed and revealed to be able to adhere both human and mouse-adapted H. pylori strains without cytotoxicity towards human gastric cells. Ex vivo studies showed that smaller (XS) microspheres penetrate further within the gastric foveolae, suggesting their ability to reach deeply adherent bacteria. In vivo assays showed 88% reduction of infection when H. pylori-infected mice (C57BL/6) were treated with more mucoadhesive XL6 and XS6 ChMics. Overall, ChMics clearly demonstrate ability to reduce H. pylori gastric infection in mice, with chitosan degree of acetylation being a dominant factor over microspheres' size on H. pylori removal efficiency. These results evidence the strong potential of this strategy as an antibiotic-free approach to fight H. pylori infection, where microspheres are orally administered, bind H. pylori in the stomach, and remove them through the gastrointestinal tract. STATEMENT OF SIGNIFICANCE: Approximately 90% of gastric cancers are caused by the carcinogenic agent Helicobacter pylori, which infects >50% of the world population. Bacterial resistance, reduced antibiotic bioavailability, and the intricate distribution of bacteria in mucus and within gastric foveolae hamper the success of most strategies to fight H. pylori. We demonstrate that an antibiotic-free therapy based on bare chitosan microspheres that bind and remove H. pylori from stomach can achieve 88% reduction of infection from H. pylori-infected mice. Changing size and mucoadhesive properties, microspheres can reach different areas of gastric mucosa: smaller and less mucoadhesive can penetrate deeper into the foveolae. This promising, simple and inexpensive strategy paves the way for a faster bench-to-bedside transition, therefore holding great potential for clinical application.

Chitosan as a Natural Copolymer with Unique Properties for the Development of Hydrogels

Hydrogel-based polymers are represented by those hydrophilic polymers having functional groups in their chain such as amine (NH2), hydroxyl [-OH], amide (-CONH-, -CONH2), and carboxyl [COOH]. These hydrophilic groups raise their potential to absorb fluids or aqueous solution more than their weights. This physicochemical mechanism leads to increased hydrogel expansion and occupation of larger volume, the process which shows in swelling behavior. With these unique properties, their use for biomedical application has been potentially raised owing also to their biodegradability and biocompatibility. Chitosan as a natural copolymer, presents a subject for hydrogel structures and function. This review aimed to study the structure as well as the function of chitosan and its hydrogel properties.

Fabrication of Mucoadhesive-Dendrimers as Solid Dosage Forms

Mucoadhesion has a potential role in the delivery of pharmaceutical medicaments via various routes of administration, viz. oral, nasal, vaginal, and buccal. Mucoadhesion provides controlled drug delivery, sustained drug delivery, and local or site-specific drug delivery. This chapter focuses on the mechanism of bio-adhesion to glycoprotein layer of mucosal membrane. Some of the gastric mucoadhesive solid dosage forms of nanocarrier, viz. nanoparticle, microsphere, and nanofibers, undergo evaluation of mucoadhesive parameters. That includes mucoadhesive strength, tensile strength, swelling index, stability studies, in vivo study, etc. The oral route is the most desirable way among intravenous, subcutaneous, intramuscular, intranasal, intravaginal, etc. for drug delivery and because of patient compliance. One of the novel approaches is where nanocarrier is loaded in the solid dosage form for effective drug action and enhanced local delivery of a drug. Mainly this chapter explains about dendrimer-based oral solid dosage form (tablet) employing mucoadhesive polymers with an aim to improve retention time of drug at desired sites. Dendrimer-loaded mucoadhesive tablets promise controlled drug delivery with a gastro-retentive property, higher drug incorporation, ease of formulation development, and accessible absorption, owing to adjacent interaction with a biological membrane and prolonged retention to mucosa providing higher bioavailability of drugs.

An Overview of Chitosan Nanoparticles and Its Application in Non-Parenteral Drug Delivery

The focus of this review is to provide an overview of the chitosan based nanoparticles for various non-parenteral applications and also to put a spotlight on current research including sustained release and mucoadhesive chitosan dosage forms. Chitosan is a biodegradable, biocompatible polymer regarded as safe for human dietary use and approved for wound dressing applications. Chitosan has been used as a carrier in polymeric nanoparticles for drug delivery through various routes of administration. Chitosan has chemical functional groups that can be modified to achieve specific goals, making it a polymer with a tremendous range of potential applications. Nanoparticles (NP) prepared with chitosan and chitosan derivatives typically possess a positive surface charge and mucoadhesive properties such that can adhere to mucus membranes and release the drug payload in a sustained release manner. Chitosan-based NP have various applications in non-parenteral drug delivery for the treatment of cancer, gastrointestinal diseases, pulmonary diseases, drug delivery to the brain and ocular infections which will be exemplified in this review. Chitosan shows low toxicity both in vitro and some in vivo models. This review explores recent research on chitosan based NP for non-parenteral drug delivery, chitosan properties, modification, toxicity, pharmacokinetics and preclinical studies.

Nano-therapeutics: A revolution in infection control in post antibiotic era

With the arrival of antibiotics 70 years ago, meant a paradigm shift in overcoming infectious diseases. For decades, drugs have been used to treat different infections. However, with time bacteria have become resistant to multiple antibiotics, making some diseases difficult to fight. Nanoparticles (NPs) as antibacterial agents appear to have potential to overcome such problems and to revolutionize the diagnosis and treatment of bacterial infections. Therefore, there is significant interest in the use of NPs to treat variety of infections, particularly caused by multidrug-resistant (MDR) strains. This review begins with illustration of types of NPs followed by the literature of current research addressing mechanisms of NPs antibacterial activity, steps involved in NP mediated drug delivery as well as areas where NPs use has potential to improve the treatment, like NP enabled vaccination. Besides, recently emerged innovative NP platforms have been highlighted and their progress made in each area has been reviewed.

The potential of nanoparticles in stem cell differentiation and further therapeutic applications

Tissue regeneration could offer therapeutic advantages for individuals experiencing organ or tissue damage. Recently, advances in nanotechnology have provided various nanomaterials, with a wide range of applications, for modulating stem cell behavior and for further therapeutic applications in tissue regeneration. Defects in cell proliferation and differentiation, a low mechanical strength of scaffolds, and inefficient production of factors that are essential for stem cell differentiation are the current challenges in tissue regeneration. This review provides a brief explanation about the link between nanotechnology and tissue engineering, highlighting the current literature about the interaction between nanoparticles (NPs) and stem cells, the promotional effect of NPs on stem cell differentiation into various lineages, and their possible therapeutic applications. We also tried to describe the mechanism through which NPs regulate the spatial-temporal release and kinetics of vital growth and differentiation factors, enhance stem cell differentiation, and improve culture conditions for in vivo tissue regeneration. The field of nanotechnology is promising and provides novel nanomaterials and methods with valuable clinical applications in the regenerative medicine. Understanding the mechanism, as well as the toxic effects of NPs in stem cell biology will undoubtedly provide valuable insight into their clinical application in the regenerative medicine.

Bacteria-targeted biomaterials: Glycan-coated microspheres to bind Helicobacter pylori

Gastric cancer is the third leading cause of cancer related deaths worldwide and Helicobacter pylori (H. pylori) persistent infection has been pointed as a causative agent of this disease. Current antibiotic based treatments to eradicate this bacterium fail in 20% of the patients, potentially leaving 140 million people in the world without alternative therapy. It is herein proposed the use of azide-alkyne coupling ("click chemistry") to produce glycan-coated mucoadhesive microspheres that bind and remove the H. pylori adherent to the gastric mucosa through specific bacterial adhesin-glycan interactions. Glycan immobilization is performed via chitosan's primary alcohol group, rather than the more reactive primary amines in order to preserve the amine groups that confer chitosan its mucoadhesiveness. It is shown that chitosan microspheres decorated with Lewis b glycans (Leb-Mic) bind specifically to H. pylori strains expressing the BabA adhesin (strains recognized as highly pathogenic) (∼230 bacteria/microsphere), are non-cytotoxic, are retained in the stomach of C57BL/6 mice for around 1.5h. Also, these Leb-Mic are able to prevent and remove H. pylori adhesion to gastric mucosa expressing the same glycan, in tissue sections from mice and human gastric mucosa (in vitro) and in fresh mice stomachs (ex vivo). These results provide proof-of-concept on the potential of glycan-decorated microspheres as an innovative therapeutic strategy against H. pylori and highlight the prospective of using targeted biomaterials to fight gastrointestinal infection.

STATEMENT OF SIGNIFICANCE

Gastric cancer has been associated with persistent infection by Helicobacter pylori, a bacterium that colonizes half of world population and whose available antibiotic treatment fails in 20% of cases. H. pylori adhesion to gastric epithelium is mediated between bacterial adhesins and glycans expressed in gastric mucosa. We demonstrate that these glycans can be immobilized in a controlled orientation into mucoadhesive chitosan microspheres, making them selective for different H. pylori strains. Efficacy studies (in vitro and ex vivo) with mice and human gastric mucosa that express the same glycan, revealed microspheres capacity to remove/prevent specific H. pylori adhesion, envisaging their future application as bacteria scavenging from stomach. This bacteria-binding strategy can be extrapolated to target other cells/bacteria using suitable ligands.

Current applications of nanoparticles in infectious diseases

For decades infections have been treated easily with drugs. However, in the 21st century, they may become lethal again owing to the development of antimicrobial resistance. Pathogens can become resistant by means of different mechanisms, such as increasing the time they spend in the intracellular environment, where drugs are unable to reach therapeutic levels. Moreover, drugs are also subject to certain problems that decrease their efficacy. This requires the use of high doses, and frequent administrations must be implemented, causing adverse side effects or toxicity. The use of nanoparticle systems can help to overcome such problems and increase drug efficacy. Accordingly, there is considerable current interest in their use as antimicrobial agents against different pathogens like bacteria, virus, fungi or parasites, multidrug-resistant strains and biofilms; as targeting vectors towards specific tissues; as vaccines and as theranostic systems. This review begins with an overview of the different types and characteristics of nanoparticles used to deliver drugs to the target, followed by a review of current research and clinical trials addressing the use of nanoparticles within the field of infectious diseases.

Potential application of injectable chitosan hydrogel treated with siRNA in chronic rhinosinusitis therapy

Chronic rhinosinusitis is a condition with severe clinical symptoms and limited therapeutic solutions. It has been reported that vascular endothelial growth factor (VEGF) can promote nasal epithelial cell growth and result in hyperplasia of the sinuses. Therefore, the downregulation of VEGF may inhibit the process of hyperplasia. In the present study, small interfering RNA (siRNA) targeting VEGF was used to silence the expression of VEGF, and injectable chitosan based hydrogel, which is suitable for sinus injection and exhibits long-term retention, was prepared as the siRNA carrier. Human bronchial epithelial cells were cultured directly on the hydrogel to observe the biological performance in vitro. Further in vivo effects were investigated by the injection of the hydrogel into the sinus cavity. Following the introduction of siRNA introducing, the expression of VEGF in the bronchial epithelial cells was significantly suppressed at mRNA and protein levels. The number of living cells on the gel was significantly decreased, thus resulting in the inhibition of proliferation. However, the cytoskeletal arrangement of the remaining cells were not affected substantially. The hydrogel was able to retain the siRNA for an extended duration, which enabled a sustained supply of siRNA. The in vivo sinus mucosa analysis revealed that the siRNA was able to collocate with cells and the mucosa thickness was substantially decreased. In conclusion, the results of the present study suggested that injectable chitosan based hydrogel, treated with siRNA targeting VEGF, may be used as a convenient therapeutic option for chronic rhinosinusitis.