In vitro and in vivo evaluation of biologically synthesized silver nanoparticles for topical applications: effect of surface coating and loading into hydrogels - PubMed (original) (raw)
In vitro and in vivo evaluation of biologically synthesized silver nanoparticles for topical applications: effect of surface coating and loading into hydrogels
Aml I Mekkawy et al. Int J Nanomedicine. 2017.
Abstract
In the present study, silver nanoparticles (AgNPs) were synthesized via biological reduction of silver nitrate using extract of the fungus Fusarium verticillioides (green chemistry principle). The synthesized nanoparticles were spherical and homogenous in size. AgNPs were coated with polyethylene glycol (PEG) 6000, sodium dodecyl sulfate (SDS), and β-cyclodextrin (β-CD). The averaged diameters of AgNPs were 19.2±3.6, 13±4, 14±4.4, and 15.7±4.8 nm, for PEG-, SDS-, and β-CD-coated and uncoated AgNPs, respectively. PEG-coated AgNPs showed greater stability as indicated by a decreased sedimentation rate of particles in their water dispersions. The antibacterial activities of different AgNPs dispersions were investigated against Gram-positive bacteria (methicillin-sensitive and methicillin-resistant Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli) by determination of the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs). MIC and MBC values were in the range of 0.93-7.5 and 3.75-15 µg/mL, respectively, which were superior to the reported values in literature. AgNPs-loaded hydrogels were prepared from the coated-AgNPs dispersions using several gelling agents (sodium carboxymethyl cellulose [Na CMC], sodium alginate, hydroxypropylmethyl cellulose, Pluronic F-127, and chitosan). The prepared formulations were evaluated for their viscosity, spreadability, in vitro drug release, and antibacterial activity, and the combined effect of the type of surface coating and the polymers utilized to form the gel was studied. The in vivo wound-healing activity and antibacterial efficacy of Na CMC hydrogel loaded with PEG-coated AgNPs in comparison to the commercially available silver sulfadiazine cream (Dermazin®) were evaluated. Superior antibacterial activity and wound-healing capability, with normal skin appearance and hair growth, were demonstrated for the hydrogel formulations, as compared to the silver sulfadiazine cream. Histological examination of the treated skin was performed using light microscopy, whereas the location of AgNPs in the skin epidermal layers was visualized using transmission electron microscopy.
Keywords: antibacterial activity; coating agents; green synthesis; hydrogel; silver nanoparticles; wound healing.
Conflict of interest statement
The authors report no conflicts of interest in this work.
Figures
Figure 1
Graphical chart represents the design of the study on the in vivo antibacterial activity of AgNPs. Abbreviations: AgNPs, silver nanoparticles; IP, intraperitoneal; CFU, colony-forming units; MRSA, methicillin-resistant Staphylococcus aureus; Na CMC, sodium carboxymethyl cellulose.
Figure 2
UV–visible spectrophotometric spectra of AgNPs dispersions: (1) 5 mM PEG-coated AgNPs; (2) 10 mM PEG-coated AgNPs; (3) 5 mM SDS-coated AgNPs; (4) 10 mM SDS-coated AgNPs; (5) 5 mM β-CD-coated AgNPs; (6) 10 mM β-CD-coated AgNPs; and (7) uncoated AgNPs and their solutions without AgNPs (blank solutions). Abbreviations: AgNPs, silver nanoparticles; PEG, polyethylene glycol; SDS, sodium dodecyl sulfate; β-CD, β-cyclodextrin; UV, ultraviolet.
Figure 3
Representative TEM micrographs for the aqueous dried AgNPs (100 µg AgNPs/mL): (A) uncoated AgNPs; (B) SDS-coated AgNPs; (C) PEG-coated AgNPs (×100,000); (D) β-CD-coated AgNPs (×140,000) with sizes =15.7±4.8, 13±4, 19.2±3.6, and 14±4.4 nm, respectively (n=50, bar represents 100 nm). Insets indicate histograms of AgNPs size distribution. Abbreviations: TEM, transmission electron microscopy; AgNPs, silver nanoparticles; SDS, sodium dodecyl sulfate; PEG, polyethylene glycol; β-CD, β-cyclodextrin.
Figure 4
Effect of coating type on AgNPs (500 µg AgNPs/mL) sedimentation rate in water over time: (a) 5 mM PEG-coated AgNPs; (b) 10 mM PEG-coated AgNPs; (c) 5 mM SDS-coated AgNPs; (d) 10 mM SDS-coated AgNPs; (e) 5 mM β-CD-coated AgNPs; (f) 10 mM β-CD-coated AgNPs; and (g) uncoated AgNPs. Abbreviations: AgNPs, silver nanoparticles; PEG, polyethylene glycol; SDS, sodium dodecyl sulfate; β-CD, β-cyclodextrin.
Figure 5
Bacterial inhibition zones of AgNPs-loaded hydrogels against MSSA, MRSA, and Escherichia coli using agar-well diffusion method, where F1–F5, F6–F10, F11–F15, F16–F20, and F21–F25 are Na CMC, Na alginate, HPMC, Pluronic F-127, and chitosan hydrogels loaded with AgNPs, respectively. Abbreviations: AgNPs, silver nanoparticles; MSSA, methicillin-sensitive Staphylococcus aureus; MRSA, methicillin-resistant S. aureus; Na CMC, sodium carboxymethyl cellulose; Na alginate, sodium alginate; HPMC, hydroxypropylmethyl cellulose.
Figure 6
Percent of wound contraction in rats during the 10 d of treatment. Hydrogel loaded with 0.1% AgNPs (circles) was compared to 1% silver sulfadiazine cream (squares). Abbreviation: AgNPs, silver nanoparticles.
Figure 7
Successive images of representative mice skin abrasion wounds infected with MRSA at different time intervals. Two groups were treated with 0.1% AgNPs hydrogel and 1% silver sulfadiazine cream. The two other groups were the blank hydrogel-treated group and control untreated mice. Abbreviations: MRSA, methicillin-resistant Staphylococcus aureus; AgNPs, silver nanoparticles.
Figure 8
Bacterial count in the infected abrasion wounds of different mice groups at different time intervals expressed as percentages of the bacterial counts in the control untreated mice group. The studied groups are 0.1% AgNPs hydrogel-treated group, 1% silver sulfadiazine cream-treated group, and blank hydrogel-treated group. Abbreviation: AgNPs, silver nanoparticles.
Figure 9
Light microscopy images of representative skin samples (stained with hematoxylin and eosin) (×400) after 15 d of treatment: (A) 0.1% AgNPs hydrogel-treated group; (B) 1% silver sulfadiazine cream-treated group; (C) blank hydrogel-treated group; and (D) control group (untreated mice). Arrows refer to lymphocytes. C, G, S, D, and E represent stratum corneum, stratum granulosum, stratum spinosum, dermis, and epidermis, respectively. Abbreviation: AgNPs, silver nanoparticles.
Figure 10
Transmission electron micrographs: (A) epidermal layers with magnification of stratum corneum; (B) epidermal layers with magnification of stratum granulosum (×4,800, inset: ×29,000), (C) Langerhans cell in stratum spinosum (×19,000, inset: ×72,000). Inset arrows indicate localized AgNPs. C, G, S, N, BG, and M represent stratum corneum, stratum granulosum, stratum spinosum, nucleus, Birbeck granules, and mitochondria, respectively. Abbreviation: AgNPs, silver nanoparticles.
References
- Birla SS, Tiwari VV, Gade AK, Ingle AP, Yadav AP, Rai MK. Fabrication of silver nanoparticles by Phoma glomerata and its combined effect against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. Lett Appl Microbiol. 2009;48(2):173–179. -PubMed
- Brandt O, Mildner M, Egger AE, et al. Nanoscalic silver possesses broad-spectrum antimicrobial activities and exhibits fewer toxicological side effects than silver sulfadiazine. Nanomedicine. 2012;8(4):478–488. -PubMed
- Keat CL, Aziz A, Eid AM, Elmarzugi NA. Biosynthesis of nanoparticles and silver nanoparticles. Bioresour Bioprocess. 2015;2(47):1–11.
- Vasilev K, Cook J, Griesser HJ. Antibacterial surfaces for biomedical devices. Expert Rev Med Devices. 2009;6(5):553–567. -PubMed
MeSH terms
Substances
LinkOut - more resources
Full Text Sources
Other Literature Sources