Recent advances of antibacterial starch-based materials

Starch has attracted a lot of attention because it is biodegradable, renewable, nontoxic and low cost. By adding antibacterial substances to starch, starch-based materials have antibacterial properties. The composite with other materials can improve the comprehensive performance of starch-based materials, thus broadening the application field of the material. In this paper, we focus on antibacterial starch-based materials and review their preparation and applications. It was found that antibacterial starch-based materials were most widely used in packaging, followed by medicine, and the research on smart starch-based materials was relatively less. This review may provide some reference value for subsequent studies of starch-based materials.

Understanding of supramolecular emulsion interfacial polymerization in silico

The composition and structure of a membrane determine its functionality and practical application. We study the supramolecular polymeric membrane prepared by supramolecular emulsion interfacial polymerization (SEIP) on the oil-in-water droplet via the computer simulation method. The factors that may influence its structure and properties are investigated, such as the degree of polymerization and molecular weight distribution (MWD) of products in the polymeric membranes. We find that the SEIP can lead to a higher total degree of polymerization as compared to the supramolecular interfacial polymerization (SIP). However, the average chain length of products in the SEIP is lower than that of the SIP due to its obvious interface curvature. The stoichiometric ratio of reactants in two phases will affect the MWD of the products, which further affects the performance of the membranes in practical applications, such as drug release rate and permeability. Besides, the MWD of the product by SEIP obviously deviates from the Flory distribution as a consequence of the curvature of reaction interface. In addition, we obtain the MWD for the emulsions whose size distribution conforms to the Gaussian distribution so that the MWD may be predicted according to the corresponding emulsion size distribution. This study helps us to better understand the controlling factors that may affect the structure and properties of supramolecular polymeric membranes by SEIP.

Nanoemulsions for synthesis of biomedical nanocarriers

Nanoemulsions are kinetically stabilized emulsions with droplet sizes in the nanometer scale. These nanodroplets are able to confine spaces in which reactions of polymerization or precipitation can take place, leading to the formation of particles and capsules that can act as nanocarriers for biomedical applications. This review discusses the different possibilities of using nanoemulsions for preparing biomedical nanocarriers. According to the chemical nature, nanocarriers prepared in nanoemulsions are classified in polymeric, inorganic, or hybrid. The main synthetic strategies for each type are revised, including miniemulsion polymerization, nanoemulsion-solvent evaporation, spontaneous emulsification, sol-gel processes, and combination of different techniques to form multicomponent materials.

Starch-based magnetic nanocomposite for targeted delivery of hydrophilic bioactives as anticancer strategy

Magnetic nanocomposites were synthesized for the targeted delivery of hydrophilic bioactives through guidance generated by a magnetic field. Superparamagnetic iron oxide nanoparticles (SPIONs) were used to generate hydroxyethyl starch magnetic nanocapsules (HES MNCs). This synthesis allowed the co-encapsulation of oncocalyxone A (onco A) and surface-modified magnetite nanoparticles (Fe₃O₄@citrate) into the same nanostructure. The synthesized nanocapsules exhibited a core-shell morphology, with an average diameter of 143 nm. This nanocomposite showed potential anticancer activity (IC₅₀) against four human tumor cell lines: glioblastoma SNB-19 (1.010 μgmL^-1), colon carcinoma HCT-116 (2.675 μgmL^-1), prostate PC3 (4.868 μgmL^-1), and leukemia HL-60 (2.166 μgmL^-1). Additionally, in vivo toxicity and locomotor activity were evaluated in a zebrafish (Danio rerio) model. The nanocomposite exhibited in vitro cytotoxicity, prolonged drug release profile and also responded to an applied magnetic field, representing a versatile compound with perspectives for highest concentration of different hydrophilic bioactives in a target tissue through magnetic vectorization.

Crosslinked polymer nanocapsules for therapeutic, diagnostic, and theranostic applications

Crosslinked polymer nanocapsules (CPNCs) are hollowed nanoparticles with network-like polymeric shells stabilized by primary bonds. CPNCs have drawn broad and significant interests as nanocarriers for biomedical applications in recent years. As compared with conventional polymeric nanoparticles systems without cavity and/or crosslinking architectures, CPNCs possess significant biomedical relevant advantages, including (a) superior structural stability against environmental conditions, (b) high loading capacity and ability for region-specific loading of multiple cargos, (c) tuneable cargo release rate via crosslinking density, and (d) high specific surface area to facilitate surface adsorption, modification, and interactions. With appropriate base polymers and crosslinkages, CPNCs can be biocompatible and biodegradable. While CPNC-based biomedical nanoplatforms can possess relatively stable physicochemical properties owing to their crosslinked architectures, various biomedically relevant stimuli-responsivities can be incorporated with them through specific structural designs. CPNCs have been studied for the delivery of small molecule drugs, genes, proteins, and other therapeutic agents. They have also been investigated as diagnostic platforms for magnetic resonance imaging, ultrasound imaging, and optical imaging. Moreover, CPNCs have been utilized to carry both therapeutics and bioimaging agents for theranostic applications. This article reviews the therapeutic, diagnostic and theranostic applications of CPNCs, as well as the preparation of these CPNCs, reported in the past decade. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Implantable Materials and Surgical Technologies > Nanomaterials and Implants Diagnostic Tools > in vivo Nanodiagnostics and Imaging.

The Impact of Engineered Silver Nanomaterials on the Immune System

Over the last decades there has been a tremendous volume of research efforts focused on engineering silver-based (nano)materials. The interest in silver has been mostly driven by the element capacity to kill pathogenic bacteria. In this context, the main area of application has been medical devices that are at significant risk of becoming colonized by bacteria and subsequently infected. However, silver nanomaterials have been incorporated in a number of other commercial products which may or may not benefit from antibacterial protection. The rapid expansion of such products raises important questions about a possible adverse influence on human health. This review focuses on examining currently available literature and summarizing the current state of knowledge of the impact of silver (nano)materials on the immune system. The review also looks at various surface modification strategies used to generate silver-based nanomaterials and the immunomodulatory potential of these materials. It also highlights the immune response triggered by various silver-coated implantable devices and provides guidance and perspective towards engineering silver nanomaterials for modulating immunological consequences.

Droplet Imbibition Enables Nonequilibrium Interfacial Reactions in Charged Microdroplets

A droplet imbibition experiment is proposed to study interfacial effects, which appears to be the main factor influencing reaction acceleration in charged microdroplets produced by electrospray ionization (ESI). One reagent is deposited onto the surface of rapidly moving microdroplets containing the second reagent to be reacted. In this manner, reactions are hindered from reaching equilibrium and monitored in real time by mass spectrometry. We demonstrated this phenomenon using Katritzky chemistry, which is known to proceed either by the solvent-stabilized 2H-pyran intermediate or via the surface-active pseudobase intermediate. Comparisons with reactions performed using ESI show obvious surface effects in favor of the droplet imbibition experiment. By keeping reactant mole ratio constant, it was demonstrated that similar interfacial effects observed in the droplet imbibition experiment can be reached by allowing ESI microdroplets containing premixed reagents to traverse a distance >16 mm. At such spray distance, molecular diffusion and droplet lifetime become comparable allowing reactants to be enriched at droplet surface. Reactions were also conducted in rapid mixing, theta capillary-based droplets, which showed markedly reduced yields compared with the interfacial droplet imbibition experiment.

Nanoengineered Antibacterial Coatings and Materials: A Perspective

This feature article begins by outlining the problem of infection and its implication on healthcare. The initial introductory section is followed by a description of the four distinct classes of antibacterial coatings and materials, i.e., bacteria repealing, contact killing, releasing and responsive, that were developed over the years by our team and others. Specific examples of each individual class of antibacterial materials and a discussion on the pros and cons of each strategy are provided. The article contains a dedicated section focused on silver nanoparticle based coatings and materials, which have attracted tremendous interest from the scientific and medical communities. The article concludes with the author’s view regarding the future of the field.

Emulsion and miniemulsion techniques in preparation of polymer nanoparticles with versatile characteristics

In recent years, polymer nanoparticles (PNPs) have found their ways into numerous applications extending from electronics to photonics, conducting materials to sensors and medicine to biotechnology. Physical properties and surface morphology of PNPs are the most important parameters that significantly affect on their exploitations and can be controlled through the synthesis process. Emulsion and miniemulsion techniques are among the most efficient and wide-spread methods for preparation of PNPs. The objective of this review is to present and highlight the recent developments in the advanced PNPs with specific properties that are produced through emulsion and miniemulsion processes.

Fully degradable protein nanocarriers by orthogonal photoclick tetrazole-ene chemistry for the encapsulation and release

The encapsulation of sensitive drugs into nanocarriers retaining their bioactivity and achieving selective release is a challenging topic in current drug delivery design. Established protocols rely on metal-catalyzed or unspecific reactions to build the (mostly synthetic) vehicles which may inhibit the drug's function. Triggered by light, the mild tetrazole-ene cycloaddition enables us to prepare protein nanocarriers (PNCs) preserving at the same time the bioactivity of the sensitive antitumor and antiviral cargo Resiquimod (R848). This catalyst-free reaction was designed to take place at the interface of aqueous nanodroplets in miniemulsion to produce core-shell PNCs with over 90% encapsulation efficiency and no unwanted drug release over storage for several months. Albumins used herein are major constituents of blood and thus ideal biodegradable natural polymers for the production of such nanocarriers. These protein carriers were taken up by dendritic cells and the intracellular drug release by enzymatic degradation of the protein shell material was proven. Together with the thorough colloidal analysis of the PNCs, their stability in human blood plasma and the detailed protein corona composition, these results underline the high potential of such naturally derived drug delivery vehicles.

Enhanced Cellular Internalization: A Bactericidal Mechanism More Relative to Biogenic Nanoparticles than Chemical Counterparts

Biogenic synthesis of silver nanoparticles for enhanced antimicrobial activity has gained a lot of momentum making it an urgent need to search for a suitable biocandidate which could be utilized for efficient capping and shaping of silver nanoparticles with enhanced bactericidal activity utilizing its secondary metabolites. Current work illustrates the enhancement of antimicrobial efficacy of silver nanoparticles by reducing and modifying their surface with antimicrobial metabolites of cell free filtrate of Trichoderma viride (MTCC 5661) in comparison to citrate stabilized silver nanoparticles. Nanoparticles were characterized by visual observations, UV-visible spectroscopy, zetasizer, and transmission electron microscopy (TEM). Synthesized particles were monodispersed, spherical in shape and 10-20 nm in size. Presence of metabolites on surface of biosynthesized silver nanoparticles was observed by gas chromatography-mass spectroscopy (GC-MS), energy dispersive X-ray analysis (EDAX), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The antimicrobial activity of both silver nanoparticles was tested against Shigella sonnei, Pseudomonas aeruginosa (Gram-negative) and Staphylococcus aureus (Gram-positive) by growth inhibition curve analysis and colony formation unit assay. Further, it was noted that internalization of biosynthesized nanoparticles inside the bacterial cell was much higher as compared to citrate stabilized particles which in turn lead to higher production of reactive oxygen species. Increase in oxidative stress caused severe damage to bacterial membrane enhancing further uptake of particles and revoking other pathways for bacterial disintegration resulting in complete and rapid death of pathogens as evidenced by fluorescein diacetate/propidium iodide dual staining and TEM. Thus, study reveals that biologically synthesized silver nanoarchitecture coated with antimicrobial metabolites of T. viride was more potent than their chemical counterpart in killing of pathogenic bacteria.

A novel in situ silver/hyaluronan bio-nanocomposite fabrics for wound and chronic ulcer dressing: In vitro and in vivo evaluations

In-situ formed hyaluronan/silver (HA/Ag) nanoparticles (NPs) were used to prepare composite fibers/fabrics for the first time. Different concentrations of silver nitrate (1, 2mg/100ml) were added at ambient temperature to sodium hyaluronate solution (40mg/ml), then the pH was increased to 8 by adding sodium hydroxide. The in-situ formed HA/Ag-NPs were used to prepare fibers/nonwoven fabrics by wet-dry-spinning technique (WDST). UV/vis spectroscopy, SEM, TEM, DLS, XPS, XRD and TGA were employed to characterize the structure and composition of the nanocomposite, surface morphology of fiber/fabrics, particle size of Ag-NPs, chemical interactions of Ag⁰ and HA functional groups, crystallinity and thermal stability of the wound dressing, respectively. The resultant HA/Ag-NPs1 and HA/Ag-NPs2 composite showed uniformly dispersed throughout HA fiber/fabrics (SEM), an excellent distribution of Ag-NPs with 25±2, nm size (TEM, DLS) and acceptable mechanical properties. The XRD analysis showed that the in-situ preparation of Ag-NPs increased the crystallinity of the resultant fabrics as well as the thermal stability. The antibacterial performance of medical HA/Ag-NPs fabrics was evaluated against gram negative bacteria E. coli K12, exhibiting significant bactericidal activity. The fibers did not show any cytotoxicity against human keratinocyte cell line (HaCaT). In-vivo animal tests indicated that the prepared wound dressing has strong healing efficacy (non-diabetics/diabetics rat model) compared to the plain HA fabrics and greatly accelerated the healing process. Based on our results, the new HA/Ag-NPs-2mg nonwoven wound dressing fabrics can be used in treating wounds and chronic ulcers as well as cell carrier in different biological research and tissue engineering.

'Chocolate' silver nanoparticles: Synthesis, antibacterial activity and cytotoxicity

HYPOTHESIS

Silver nanoparticles (AgNPs) have emerged as a powerful weapon against antibiotic resistant microorganisms. However, most conventional AgNPs syntheses require the use of hazardous chemicals and generate toxic organic waste. Hence, in recent year's, plant derived and biomolecule based synthetics have has gained much attention. Cacao has been used for years for its medicinal benefits and contains a powerful reducing agent - oxalic acid. We hypothesized that, due to the presence of oxalic acid, cacao extract is capable of reducing silver nitrate (AgNO3) to produce AgNPs.

EXPERIMENTS

In this study, AgNPs were synthesized by using natural cacao extract as a reducing and stabilizing agent. The reaction temperature, time and reactant molarity were varied to optimize the synthesis yield.

FINDINGS

UV-visible spectroscopy (UV-vis), dynamic light scattering (DLS) and transmission electron microscopy (TEM) characterization demonstrated that the synthesized AgNPs were spherical particles ranging in size from 35 to 42.5nm. The synthesized AgNPs showed significant antibacterial activity against clinically relevant pathogens such as Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Staphylococcus epidermidis. Importantly, these green AgNPs are not cytotoxic to human dermal fibroblasts (HDFs) at concentrations below 32μg/ml. We conclude that cacao-based synthesis is a reproducible and sustainable method for the generation of stable antimicrobial silver nanoparticles with low cytotoxicity to human cells. The AgNPs synthesized in this work have promising properties for applications in the biomedical field.

Novel amino acid based nanogel conjugated suture for antibacterial application

In this study, a promising preparation strategy for antibacterial silk sutures with an l-lysine based nanogel grafting is reported.

Phytochemically Functionalized Cu and Ag Nanoparticles Embedded in MWCNTs for Enhanced Antimicrobial and Anticancer Properties

Nanomedicine is an emerging field concerned with the use of precision engineered nanomaterials, which leads to the development of novel remedial and diagnostic modalities for human use. In this study, Cu(NO3)2 and AgNO3 precursors were reduced to copper nanoparticles (CuNPs) and silver nanoparticles (AgNPs) using Terminalia arjuna bark extracts under microwave irradiation in the presence of well-dispersed multi-walled carbon nanotubes (MWCNTs) in aqueous medium. The formation of CuNPs or AgNPs and their functionalization with MWCNTs via bioactive molecules of plant extract were evidenced from UV-Vis spectra, XRD, FTIR, FESEM, EDX, and TEM images. The phytochemically functionalized Cu-MWCNTs and Ag-MWCNTs nanomaterials showed enhanced biocide activity, and the inhibitory activity for bacteria was higher than that of fungus. Furthermore, these biohybrid nanomaterials are non-toxic to normal epithelial cells (Vero), whereas they are highly toxic for tested human cancer cells of MDA-MB-231, HeLa, SiHa, and Hep-G2. The cell viability was found to decrease with the increasing dose from 10 to 50 µg mL-1, as well as incubation time from 24 to 72 h. For instance, the cell viability was found to be ~91 % for normal Vero cells and ~76 % for cancer cells for lower dose of 10 µg mL-1.

Zinc-triggered hydrogelation of self-assembled small molecules to inhibit bacterial growth

There is a significant need to develop antibacterial materials that could be applied locally and directly to the places surrounded by large amount of bacteria, in order to address the problems of bacterial antibiotic-resistance or irreversible biofilm formation. Hydrogels are thought to be suitable candidates due to their versatile applications in biomedical field. Among them, small molecular hydrogels have been paid lots of attention because they are easy to design and fabricate and often sensitive to external stimuli. Meanwhile, the antibacterial activity of metal ions are attracting more and more attention because resistance to them are not yet found within bacteria. We therefore designed the zinc ion binding peptide of Nap-GFFYGGGHGRGD, who can self-assemble into hydrogels after binds Zn(2+) and inhibit the growth of bacteria due to the excellent antibacterial activity of Zn(2+). Upon the addition of zinc ions, solutions containing Nap-GFFYGGGHGRGD transformed into supramolecular hydrogels composed of network of long nano-fibers. Bacterial tests revealed an antibacterial effect of the zinc triggered hydrogels on E. coli. The studied small molecular hydrogel shows great potential in locally addressing bacterial infections.

Carbohydrate nanocarriers in biomedical applications: functionalization and construction

Carbohydrates are used to functionalize or construct nanocarriers for biomedical applications – specific targeting, biocompatibility, stealth effect, biodegradability.

Biopolymer colloids for controlling and templating inorganic synthesis

Biopolymers and biopolymer colloids can act as controlling agents and templates not only in many processes in nature, but also in a wide range of synthetic approaches. Inorganic materials can be either synthesized ex situ and later incorporated into a biopolymer structuring matrix or grown in situ in the presence of biopolymers. In this review, we focus mainly on the latter case and distinguish between the following possibilities: (i) biopolymers as controlling agents of nucleation and growth of inorganic materials; (ii) biopolymers as supports, either as molecular supports or as carrier particles acting as cores of core-shell structures; and (iii) so-called "soft templates", which include on one hand stabilized droplets, micelles, and vesicles, and on the other hand continuous scaffolds generated by gelling biopolymers.

Synthesis and surface immobilization of antibacterial hybrid silver-poly(l-lactide) nanoparticles

Infections associated with medical devices are a substantial healthcare problem. Consequently, there has been increasing research and technological efforts directed toward the development of coatings that are capable of preventing bacterial colonization of the device surface. Herein, we report on novel hybrid silver loaded poly(L-lactic acid) nanoparticles (PLLA-AgNPs) with narrowly distributed sizes (17 ± 3 nm) prepared using a combination of solvent evaporation and mini-emulsion technology. These particles were then immobilized onto solid surfaces premodified with a thin layer of allylamine plasma polymer (AApp). The antibacterial efficacy of the PLLA-AgNPs nanoparticles was studied in vitro against both gram-positive (Staphylococcus epidermidis) and gram-negative (Escherichia coli) bacteria. The minimal inhibitory concentration values against Staphylococcus epidermidis and Escherichia coli were 0.610 and 1.156 μg · mL(-1), respectively. The capacity of the prepared coatings to prevent bacterial surface colonization was assessed in the presence of Staphylococcus epidermidis, which is a strong biofilm former that causes substantial problems with medical device associated infections. The level of inhibition of bacterial growth was 98%. The substrate independent nature and the high antibacterial efficacy of coatings presented in this study may offer new alternatives for antibacterial coatings for medical devices.

Green silver nanobioarchitectures with amplified antioxidant and antimicrobial properties

A novel, simple and cost-effective bottom-up approach was developed to achieve antioxidant and antimicrobial biohybrids based on biomimetic membranes, phyto-nanosilver and single-walled carbon nanotubes.