New achievements in the realm of nanoscience and innovative techniques of nanomedicine have moved micro/nanoparticles (MNPs) to the point of becoming actually useful for practical applications in the near future. Various differences between the extracellular and intracellular environments of cancerous and normal cells and the particular characteristics of tumors such as physicochemical properties, neovasculature, elasticity, surface electrical charge, and pH have motivated the design and fabrication of inventive “smart” MNPs for stimulus-responsive controlled drug release. These novel MNPs can be tailored to be responsive to pH variations, redox potential, enzymatic activation, thermal gradients, magnetic fields, light, and ultrasound (US), or can even be responsive to dual or multi-combinations of different stimuli. This unparalleled capability has increased their importance as site-specific controlled drug delivery systems (DDSs) and has encouraged their rapid development in recent years. An in-depth understanding of the underlying mechanisms of these DDS approaches is expected to further contribute to this groundbreaking field of nanomedicine. Smart nanocarriers in the form of MNPs that can be triggered by internal or external stimulus are summarized and discussed in the present review, including pH-sensitive peptides and polymers, redox-responsive micelles and nanogels, thermo- or magnetic-responsive nanoparticles (NPs), mechanical- or electrical-responsive MNPs, light or ultrasound-sensitive particles, and multi-responsive MNPs including dual stimuli-sensitive nanosheets of graphene. This review highlights the recent advances of smart MNPs categorized according to their activation stimulus (physical, chemical, or biological) and looks forward to future pharmaceutical applications.

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Smart micro/nanoparticles in stimulus-responsive drug/gene delivery systems

Despite numerous existing potent antibiotics and other antimicrobial means, bacterial infections are still a major cause of morbidity and mortality. Moreover, the need to develop additional bactericidal means has significantly increased due to the growing concern regarding multidrug-resistant bacterial strains and biofilm associated infections. Consequently, attention has been especially devoted to new and emerging nanoparticle-based materials in the field of antimicrobial chemotherapy. The present review discusses the activities of nanoparticles as an antimicrobial means, their mode of action, nanoparticle effect on drug-resistant bacteria, and the risks attendant on their use as antibacterial agents. Factors contributing to nanoparticle performance in the clinical setting, their unique properties, and mechanism of action as antibacterial agents are discussed in detail.

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Alternative Antimicrobial Approach: Nano-Antimicrobial Materials

Metal oxide nanoparticles as antimicrobial agents: a promise for the future

Current applications of nanoparticles in infectious diseases.

Quorum sensing inhibitors as antipathogens: biotechnological applications.

The effectiveness of the metal oxide nanoparticles viz. CuO and Fe2O3 as antibacterial agents against multidrug resistant biofilm forming bacteria was evaluated. CuO nanoparticles were also experimented for antibiofilm and time kill assay. The CuO displayed maximum antibacterial activity with zone of inhibition of (22 ± 1) mm against methicillin resistant Staphylococcus aureus (MRSA) followed by Escherichia coli (18 ± 1) mm. The Fe2O3 showed the zone of inhibition against MRSA of (14 ± 1) mm followed by E. coli (12 ± 1) mm. CuO proved to be more toxic than Fe2O3 nanoparticles showing significantly high antibacterial activity and found to possess dose dependent antibiofilm properties.

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Comparative study of antibiofilm activity of copper oxide and iron oxide nanoparticles against multidrug resistant biofilm forming uropathogens.

Foley's catheters were coated with Silver (Ag), plasma polymerized aniline (PPAni) and Ag−PPAni composite by plasma based deposition processes which were characterized by XRD, EDX, SEM, and FT-IR spectroscopy and bioassays were performed to validate their efficacies to kill planktonic cells as well as to remove biofilm. The analyses confirmed the formation of Ag nanoparticles (AgNPs), PPAni and Ag−PPAni composite and also corroborated their successful deposition over the catheters. Antibacterial assays showed that coated catheters were capable of killing planktonic cells of most commonly encountered uropathogens and equally capable of eradicating biofilm formation by the uropathogens as evident from the reduced cfu/ml. UV–vis spectroscopy results showed that the nanoparticle coated catheters were capable of gradual release of AgNPs, killing all planktonic cells in solution over the time. Foley's catheters coated with AgNPs and their composites by one step plasma process were non-toxic devices capable of killing planktonic cells and proficient in eradicating biofilm formation which could be used to cutback the likelihood of the catheter related complications. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 1223–1235, 2014.

Highly effective antibiofilm coating of silver–polymer nanocomposite on polymeric medical devices deposited by one step plasma process

Supramolecular association involving anion–π interactions in Cu(II) coordination solids: Experimental and theoretical studies

Fermentation of fruit and vegetable peels produces garbage enzyme (GE) which was used to obtain industrially beneficial products. This study was conducted for the characterization of GE and evaluation of its biocatalytic and antimicrobial activity. The maximum activity of amylase, protease and lipase were 1.782 units/mg, 0.050 units/mg and 0.355 units/mg respectively were found in optimum conditions which also showed antioxidant properties. The enzyme solution was separated by Fast Protein Liquid Chromatography (FPLC) and experiments were conducted for antimicrobial activity with the FPLC generated fractions of GE on both gram positive and gram negative bacteria. Inhibition zones were measured from concentration dependent bioassay analysis of lyophilized FPLC fractions. FPLC fraction II offered best zone of inhibition in Escherichia coli, Staphylococcus aureus and in Rhizobium leguminosarum. Molecular weight of above fraction was determined by SDS-PAGE technique. Significant research findings of this research work will help in developing newer potential commercializable antimicrobial agents from GE generated from fruit and vegetable waste.

Characterization and FPLC Analysis of Garbage Enzyme: Biocatalytic and Antimicrobial Activity

This study aimed to assess the antidiabetic, and antioxidant potential of Rhynchostylis retusa and Euphorbia neriifolia, well known for traditional ethnomedicinal uses in North-east India. Leaf extracts prepared in water, methanol and petroleum ether were evaluated for in vitro antidiabetic and antioxidant assay using α-amylase inhibition, glucose diffusion method and DPPH radical scavenging activity. The α-amylase inhibition with E. neriifolia methanolic extract at 400 μg/ml (66.67%) and R. retusa aqueous extract at 300 μg/ml (58.15%) were stronger than in equivalent concentrations of acarbose, i.e., 62.17, and 51.52%, respectively. Aqueous extract R. retusa showed a maximum 67.65% inhibition of glucose diffusion at 180 min in comparison to control without leaf extract. The DPPH radical scavenging activity of E. neriifolia extract in methanol was significantly better than equivalent aqueous or ether extract. However, the solvent choice had little impact on antioxidant activity in R. retusa. GC–MS analysis revealed the presence of a large number of phytochemicals in methanol fraction of E. neriifolia aqueous extracts in comparison to R. retusa. Though the in vitro α-amylase inhibition or glucose diffusion retardation implied potential medicinal use of endangered orchid R. retusa and E. neriifolia, further investigation may be warranted for identification of relevant bio-active compounds and in vivo validation of their pharmacological properties.

Bula Choudhury

Papers

Comparative study of antibiofilm activity of copper oxide and iron oxide nanoparticles against multidrug resistant biofilm forming uropathogens.

Highly effective antibiofilm coating of silver–polymer nanocomposite on polymeric medical devices deposited by one step plasma process

Supramolecular association involving anion–π interactions in Cu(II) coordination solids: Experimental and theoretical studies

Characterization and FPLC Analysis of Garbage Enzyme: Biocatalytic and Antimicrobial Activity

In vitro antidiabetic, antioxidant activities and GC–MS analysis of Rhynchostylis Retusa and Euphorbia Neriifolia leaf extracts