Peer-reviewed Articles

Please use the archived list on the right to look at past peer-reviewed articles.

2014

Caffery,B. E., Joyce,E., Heynen,M. L., Ritter,R., Jones,L. A., Senchyna,M. Quantification of conjunctival TNF-a in aqueous-deficient dry eye. Optometry and Vision Science 2014;91,2:156-162. [ Show Abstract ]

PURPOSE: This study aimed to quantify and compare conjunctival epithelial tumor necrosis factor (NF) a mRNA expression in Sjögren syndrome (SS), non-Sjögren syndrome aqueous-deficient dry eye (non-SS DE), and non-dry eye (NDE) control subjects. METHODS: A total of 76 subjects were recruited for this study: 25 SS (confirmed via American-European Consensus Criteria 2002), 25 non-SS DE (confirmed by symptoms and Schirmer scores = 10 mm), and 26 NDE. Superior and temporal bulbar conjunctival epithelial cells were collected via impression cytology. Epithelial RNA was extracted, and TNF-a mRNA expression was quantified by real-time quantitative polymerase chain reaction. RESULTS: The expression of TNF-a mRNA was found to be significantly higher in the SS group (2.48 ± 1.79) compared to both non-SS DE (0.95 ± 1.18; p < 0.05) and NDE (0.84 ± 0.51; p < 0.05) groups. No difference in TNF-a mRNA expression was found between the non-SS DE and NDE groups (p = 0.67). CONCLUSIONS: These results demonstrate that SS-associated aqueous-deficient dry eye is associated with a significant upregulation of conjunctival epithelial TNF-a mRNA relative to both non-SS DE and control groups. The degree to which TNF-a mRNA is upregulated in SS may contribute to the severe ocular surface damage observed in these patients. Copyright © 2014 American Academy of Optometry.

Cheung,S., Lorentz,H., Drolle,E., Leonenko,Z., Jones,L. W. Comparative study of lens solutions' ability to remove tear constituents. Optometry and Vision Science 2014;91,9:1045-1061. [ Show Abstract ]

PURPOSE: The purpose of this study was to use atomic force microscopy to compare and characterize the cleaning abilities of a hydrogen peroxide-based system (HPS) and a polyhexamethylene biguanide-containing multipurpose solution (MPS) at removing in vitro deposited tear film constituents, as well as to determine deposition patterns on various silicone hydrogel contact lenses. METHODS: Silicone hydrogel materials - balafilcon A (BA), lotrafilcon B (LB), and senofilcon A (SA) - were incubated for 1 week in an artificial tear solution (ATS) containing representative lipids, proteins, and salts from the tear film. Atomic force microscopy was used to resolve each lens before and after being cleaned overnight in HPS or MPS. Atomic force microscopy was used again to resolve HPS/MPS-cleaned lenses, which were reincubated in fresh ATS for 1 week, before and after an overnight clean in their respective cleaning solution. RESULTS: Atomic force microscopy imaging was able to characterize lens deposits with high resolution. Lenses incubated in ATS revealed distinct differences in their deposition pattern across lens materials. The surface of BA contained about 20-nm-high deposits, whereas deposit heights up to 150 nm completely occluded the surface of SA. Lotrafilcon B lenses revealed clusters of deposits up to 90 nm. The use of either lens solution left trace amounts of tear film constituents, although components from the MPS were seen adsorbed onto the surface after cleaning. Surface roughness (Ra) measurements revealed a significant difference between ATS-incubated and HPS/MPS-cleaned SA and LB lenses (p < 0.05). Ra between first incubated and HPS/MPS-cleaned reincubated SA and LB was also significant (p < 0.05). CONCLUSIONS: Unique variations in ATS deposition patterns were seen between lenses with atomic force microscopy. The application of both HPS and MPS removed most visible surface deposits. © American Academy of Optometry.

Gorbet,M., Peterson,R., McCanna,D., Woods,C., Jones,L., Fonn,D. Human corneal epithelial cell shedding and fluorescein staining in response to silicone hydrogel lenses and contact lens disinfecting solutions. Current eye research 2014;39,3:245-256. [ Show Abstract ]

Purpose: A pilot study was conducted to evaluate human corneal epithelial cell shedding in response to wearing a silicone hydrogel contact lens/solution combination inducing corneal staining. The nature of ex vivo collected cells staining with fluorescein was also examined. Methods: A contralateral eye study was conducted in which up to eight participants were unilaterally exposed to a multipurpose contact lens solution/silicone hydrogel lens combination previously shown to induce corneal staining (renu® fresh™ and balafilcon A; test eye), with the other eye using a combination of balafilcon A soaked in a hydrogen peroxide care system (Clear Care®; control eye). Lenses were worn for 2, 4 or 6 hours. Corneal staining was graded after lens removal. The Ocular Surface Cell Collection Apparatus was used to collect cells from the cornea and the contact lens. Results: In the test eye, maximum solution-induced corneal staining (SICS) was observed after 2 hours of lens wear (reducing significantly by 4 hours; p < 0.001). There were significantly more cells collected from the test eye after 4 hours of lens wear when compared to the control eye and the collection from the test eye after 2 hours (for both; n = 5; p < 0.001). The total cell yield at 4 hours was 813 ± 333 and 455 ± 218 for the test and control eyes, respectively (N = 5, triplicate, p = 0.003). A number of cells were observed to have taken up the fluorescein dye from the initial fluorescein instillation. Confocal microscopy of fluorescein-stained cells revealed that fluorescein was present throughout the cell cytoplasm and was retained in the cells for many hours after recovery from the corneal surface. Conclusion: This pilot study indicates that increased epithelial cell shedding was associated with a lens-solution combination which induces SICS. Our data provides insight into the transient nature of the SICS reaction and the nature of fluorescein staining observed in SICS. © 2014 Informa Healthcare USA, Inc.

Hall,B. J., Jones,L. W., Dixon,B. Silicone allergies and the eye: Fact or fiction?. Eye and Contact Lens 2014;40,1:51-57. [ Show Abstract ]

OBJECTIVE: The purpose of this manuscript was to review the evidence concerning the role of an allergic reaction to silicone as the basis for the reported increase in contact lens-associated infiltrates in wearers of silicone hydrogel contact lenses. METHODS: A literature review was undertaken to investigate the antigenic properties of silicone and the causes of contact lens-associated inflammatory reactions. RESULTS: Immune cells cannot interact with silicone directly but can interact with antigens on these lenses. These antigens could be due to tear film deposits, microbial contamination, or components of care systems used with these lenses. CONCLUSIONS: Inflammatory reactions associated with silicone hydrogel contact lens wear are not caused by an allergic reaction to silicone alone. © 2013 Contact Lens Association of Ophthalmologists.

Hall,B., McCanna,D., Jones,L. Identification of coagulase-negative staphylococci in daily disposable contact lens wearers. Letters in applied microbiology 2014;59,3:313-319. [ Show Abstract ]

This study aimed to identify and quantify the number of contaminating organisms on daily disposable (DD) soft contact lenses, which may be responsible for mild cases of keratitis that occur with this lens wear modality. Ten participants wore DD lenses, and 10 participants wore planned replacement (PR) lenses. Lenses were collected aseptically and analysed for microbial contamination. Colony-forming units (CFU) were recorded, and representative colonies were used for identification using the API identification system. The DD lenses evaluated in this study were contaminated with coagulase-negative staphylococcus (CNS), ranging from 1 to 653 CFU. PR lenses showed more diversity in the types of contaminating micro-organisms and consisted of CNS, Gram-negative bacteria (Pseudomonas), a yeast (Candida) and a mould (Aspergillus), ranging from 1 to 230 CFU. CNS was the only type of micro-organism found on DD contact lenses and therefore may be the cause of any form of keratitis observed in DD lens wearers. © 2014 The Society for Applied Microbiology.

Hall,B., Phan,C. -M, Subbaraman,L., Jones,L. W., Forrest,J. Extraction versus in Situ techniques for measuring surface-adsorbed lysozyme. Optometry and Vision Science 2014;91,9:1062-1070. [ Show Abstract ]

PURPOSE: To compare two techniques for measuring the activity of lysozyme deposited onto hydrogel contact lens and to image the binding of Micrococcus lysodeikticus to contact lenses. METHODS: Using a previously described protein extraction technique and a recently developed in situ technique, we measured the time-dependent activity of adsorbed lysozyme on six different contact lens materials during the first minute and up to 1 week of interaction with the material surface. Total activity of extracted lysozyme, total in situ activity, and the activity of the outer surface layer of sorbed lysozyme were determined using the two different techniques. Micrococcal cellular interaction with surface-adsorbed lysozyme was imaged using confocal microscopy. RESULTS: The differences between total extracted activities, total in situ activities, and surface activities were both measurable and material specific. In most cases, total extracted activity is greater than total in situ activity, which, in turn, is greater than surface activity. After 1 week, etafilcon A had the highest extracted activity at 137 µg/lens, followed by omafilcon A, balafilcon A, comfilcon A, senofilcon A, and lotrafilcon B at 27.4, 2.85, 2.02, 0.46, and 0.27 µg/lens, respectively. Micrococcal cell adhesion was greatest on contact lenses with high contact angles, such as balafilcon A, omafilcon A, and senofilcon A and lowest on contact lenses with low contact angles, such as etafilcon A, comfilcon A, and lotrafilcon B. Subsequent removal/prevention of adhered micrococcal cells was greatest on balafilcon A, which had the highest surface activity, and lowest on lotrafilcon B, which had the lowest surface activity. CONCLUSIONS: This study has measured and made direct comparisons between two established techniques for measuring the activity of adsorbed lysozyme. The extraction technique determines the activity of underlying layers of lysozyme or lysozyme within the matrix of the material. Conversely, the in situ technique allows conclusions to be drawn about only the biologically relevant lysozyme including the activity of just the outer surface of adsorbed lysozyme. © American Academy of Optometry.

Hui,A., Willcox,M., Jones,L. In vitro and in vivo evaluation of novel ciprofloxacin-releasing silicone hydrogel contact lenses. Investigative Ophthalmology and Visual Science 2014;55,8:4896-4904. [ Show Abstract ]

PURPOSE. The purpose of this study was to evaluate ciprofloxacin-releasing silicone hydrogel contact lens materials in vitro and in vivo for the treatment of microbial keratitis. METHODS. Model silicone hydrogel contact lens materials were manufactured using a molecular imprinting technique to modify ciprofloxacin release kinetics. Various contact lens properties, including light transmission and surface wettability, were determined, and the in vitro ciprofloxacin release kinetics elucidated using fluorescence spectrophotometry. The materials then were evaluated for their ability to inhibit Pseudomonas aeruginosa growth in vitro and in an in vivo rabbit model of microbial keratitis. RESULTS. Synthesized lenses had similar material properties to commercial contact lens materials. There was a decrease in light transmission in the shorter wavelengths due to incorporation of the antibiotic, but over 80% light transmission between 400 and 700 nm. Modified materials released for more than 8 hours, significantly longer than unmodified controls (P 0.05), which is significantly less than corneas treated with unmodified control lenses or those that received no treatment at all (P < 0.05). CONCLUSIONS. These novel contact lenses designed for the extended release of ciprofloxacin may be beneficial to supplement or augment future treatments of sight-threatening microbial keratitis. © 2014 The Association for Research in Vision and Ophthalmology, Inc.

Moezzi,A. M., Fonn,D., Varikooty,J., Simpson,T. L. Overnight corneal swelling with high and low powered silicone hydrogel lenses. Journal of Optometry 2014. [ Show Abstract ]

Purpose: To compare central corneal swelling after eight hours of sleep in eyes wearing four different silicone hydrogel lenses with three different powers. Methods: Twenty-nine neophyte subjects wore lotrafilcon A (Dk, 140), balafilcon A (Dk, 91), galyfilcon A (Dk, 60) and senofilcon A (Dk, 103) lenses in powers -3.00, -10.00 and +6.00 D on separate nights, in random order, and on one eye only. The contra-lateral eye (no lens) served as the control. Central corneal thickness was measured using a digital optical pachometer before lens insertion and immediately after lens removal on waking. Results: For the +6.00 D and -10.00 D, lotrafilcon A induced the least swelling and galyfilcon A the most. The +6.00 D power, averaged across lens materials, induced significantly greater central swelling than the -10.00 and -3.00 D (Re-ANOVA, p < 0.001), (7.7 ± 2.9% vs. 6.8 ± 2.8% and 6.5 ± 2.5% respectively) but there was no difference between -10.00 and -3.00 D. Averaged for power, lotrafilcon A induced the least (6.2 ± 2.8%) and galyfilcon A the most (7.6 ± 3.0%) swelling at the center (Re-ANOVA, p < 0.001). Central corneal swelling with +6.00 D was significantly greater than -10.00 D lens power despite similar levels of average lens transmissibility of these two lens powers. Conclusions: The differences in corneal swelling of the lens wearing eyes are consistent with the differences in oxygen transmission of the silicone hydrogel lenses. In silicone hydrogel lenses central corneal swelling is mainly driven by central lens oxygen transmissibility. © 2013 Spanish General Council of Optometry.

Mohammadi,S., Jones,L., Gorbet,M. Extended latanoprost release from commercial contact lenses: In vitro studies using corneal models. PLOS ONE 2014;9,9:e106653. [ Show Abstract ]

In this study, we compared, for the first time, the release of a 432 kDa prostaglandin analogue drug, Latanoprost, from commercially available contact lenses using in vitro models with corneal epithelial cells. Conventional polyHEMA-based and silicone hydrogel soft contact lenses were soaked in drug solution ( solution in phosphate buffered saline). The drug release from the contact lens material and its diffusion through three in vitro models was studied. The three in vitro models consisted of a polyethylene terephthalate (PET) membrane without corneal epithelial cells, a PET membrane with a monolayer of human corneal epithelial cells (HCEC), and a PET membrane with stratified HCEC. In the cell-based in vitro corneal epithelium models, a zero order release was obtained with the silicone hydrogel materials (linear for the duration of the experiment) whereby, after 48 hours, between 4 to 6  of latanoprost (an amount well within the range of the prescribed daily dose for glaucoma patients) was released. In the absence of cells, a significantly lower amount of drug, between 0.3 to 0.5 , was released, (). The difference observed in release from the hydrogel lens materials in the presence and absence of cells emphasizes the importance of using an in vitrocorneal model that is more representative of the physiological conditions in the eye to more adequately characterize ophthalmic drug delivery materials. Our results demonstrate how in vitro models with corneal epithelial cells may allow better prediction of in vivo release. It also highlights the potential of drug-soaked silicone hydrogel contact lens materials for drug delivery purposes.

Ngo,W., Srinivasan,S., Schulze,M., Jones,L. Repeatability of grading meibomian gland dropout using two infrared systems. Optometry and Vision Science 2014;91,6:658-667. [ Show Abstract ]

PURPOSE: To determine the interobserver and intraobserver repeatability in using the OCULUS Keratograph 4 (K4) and 5M (K5M) to grade meibomian gland (MG) dropout using meibography grading scales. METHODS: The inferior and superior eyelids of 40 participants (35 women, 5 men; mean age = 32 years) were imaged three times each on both instruments. The images were split into one training and two study sets; the latter were graded (four-point meibography scale) by two observers on two separate occasions (24 hours apart) to determine repeatability. Semiobjective quantification of percentage MG dropout was conducted using ImageJ on K4 and K5M images. A finer seven-point meibography scale was used to grade a separate set of K5M images. RESULTS: For the four-point scale, interobserver mean difference (MD) (±SD) was 0.08 (±0.55) on day 1 and 0.13 (±0.50) on day 2, and the concordance correlation coefficient (CCC) was 0.79 and 0.81 on days 1 and 2, respectively. Intraobserver MD (±SD) was 0.04 (±0.54), CCC = 0.79 for observer 1; intraobserver MD (±SD) was -0.09 (±0.60), CCC = 0.74 for observer 2. For the seven-point scale, interobserver MD (±SD) was 0.05 (±0.45), CCC = 0.89 on day 1, and interobserver MD (±SD) was 0.01 (±0.41), CCC = 0.91 on day 2. Intraobserver MD (±SD) was -0.10 (±0.35), CCC = 0.93 for observer 1, and intraobserver MD (±SD) was -0.06 (±0.30), CCC = 0.95 for observer 2. Percentage dropout measured between the K4 and K5M images showed lack of agreement, with 21.8% coefficient of repeatability. There was no significant correlation (r 0.05) between meibography score and clinical signs (corneal staining, gland expressibility, telangiectasia, vascularity, lash loss); however, there was a high correlation (r = 0.77; p < 0.05) between meibography score with percentage dropout. CONCLUSIONS: Observers graded from -1 to +1 grade units between and within themselves for a four-point scale, 95% of the time. Although the interobserver and intraobserver repeatability of the K4 and K5M were very similar, a high rate of disagreement in percentage dropout between K4 and K5M images suggests that the two instruments cannot be interchanged. Meibomian gland dropout scores did not correlate significantly with clinical signs. Using a finer scale may be beneficial for detecting change.

Phan,C. -M, Subbaraman,L. N., Jones,L. In vitro drug release of natamycin from ß-cyclodextrin and 2-hydroxypropyl-ß-cyclodextrin-functionalized contact lens materials. Journal of Biomaterials Science, Polymer Edition 2014;25,17:1907-1919. [ Show Abstract ]

Purpose: The antifungal agent natamycin can effectively form inclusion complexes with beta-cyclodextrin (ß-CD) and 2-hydroxypropyl-ß-cyclodextrin (HP-ßCD) to improve the water solubility of natamycin by 16-fold and 152-fold, respectively (Koontz, J. Agric. Food. Chem. 2003). The purpose of this study was to develop contact lens materials functionalized with methacrylated ß-CD (MßCD) and methacrylated HP-ßCD (MHP-ßCD), and to evaluate their ability to deliver natamycin in vitro. Methods: Model conventional hydrogel (CH) materials were synthesized by adding varying amounts of MßCD and MHP-ßCD (0, 0.22, 0.44, 0.65, 0.87, 1.08% of total monomer weight) to a monomer solution containing 2-hydroxyethyl methacrylate (HEMA). Model silicone hydrogel (SH) materials were synthesized by adding similar concentrations of MßCD and MHP-ßCD to N,N-dimethylacrylamide (DMAA)/10% 3-methacryloxypropyltris(trimethylsiloxy)silane (TRIS). The gels were cured with UV light, washed with ethanol and then, hydrated for 24 h (h). The model materials were then incubated with 2 mL of 100 g/mL of natamycin in phosphate buffered saline (PBS) pH 7.4 for 48 h at room temperature. The release of natamycin from these materials in 2 mL of PBS, pH 7.4 at 32 ± 2 °C was monitored using UV-vis spectrophotometry at 304 nm over 24 h. Results: For both CH and SH materials, functionalization with MßCD and MHP-ßCD improved the total amount of drugs released up to a threshold loading concentration, after which further addition of methacrylated CDs decreased the amount of drugs released (p < 0.05). The addition of CDs did not extend the drug release duration; the release of natamycin by all model materials reached a plateau after 12 h (p < 0.05). Overall, DMAA/10% TRIS materials released significantly more drug than HEMA materials (p < 0.05). The addition of MHP-ßCD had a higher improvement in drug release than MßCD for both HEMA and DMAA/10% TRIS gels (p < 0.05). Conclusions: A high loading concentration of methacrylated CDs decreases overall drug delivery efficiency, which likely results from an unfavorable arrangement of the CDs within the polymer network leading to reduced binding of natamycin to the CDs. HEMA and DMAA/10% TRIS materials functionalized with MHP-ßCD are more effective than those functionalized with MßCD to deliver natamycin.

Phan,C. -M, Subbaraman,L., Jones,L. Contact lenses for antifungal ocular drug delivery: A review. Expert Opinion on Drug Delivery 2014;11,4:537-546. [ Show Abstract ]

Introduction: Fungal keratitis, a potentially blinding disease, has been difficult to treat due to the limited number of approved antifungal drugs and the taxing dosing regimen. Thus, the development of a contact lens (CL) as an antifungal drug delivery platform has the potential to improve the treatment of fungal keratitis. A CL can serve as a drug reservoir to continuously release drugs to the cornea, while limiting drug loss through tears, blinking, drainage and non-specific absorption. Areas covered: This review will provide a summary of currently available methods for delivering antifungal drugs from commercial and model CLs, including vitamin E coating, impregnated drug films, cyclodextrin-functionalized hydrogels, polyelectrolyte hydrogels and molecular imprinting. This review will also highlight some of the main factors that influence antifungal drug delivery with CLs. Expert opinion: Several novel CL materials have been developed, capable of extended drug release profiles with a wide range of antifungal drugs lasting from 8 h to as long as 21 days. However, there are factors, such as first-order release kinetics, effectiveness of continuous drug release, microbial resistance, ocular toxicity and potential complications from inserting a CL in an infected eye, that still need to be addressed before commercial applications can be realized. © Informa UK, Ltd.

Phan,C. -M, Subbaraman,L., Liu,S., Gu,F., Jones,L. In vitro uptake and release of natamycin Dex -b- PLA nanoparticles from model contact lens materials. Journal of Biomaterials Science, Polymer Edition 2014;25,1:18-31. [ Show Abstract ]

Purpose: To evaluate the uptake and release of the antifungal agent natamycin encapsulated within poly(D,L-lactide)-dextran nanoparticles (Dex-b-PLA NPs) from model contact lens (CL) materials. Methods: Six model CL materials (gel 1:poly(hydroxyethyl methacrylate, pHEMA); gel 2:85% pHEMA: 15% [Tris(trimethylsiloxy)silyl]-propyl methacrylate (TRIS); gel 3: 75% pHEMA: 25% TRIS; gel 4: 85% N,N dimethylacrylamide (DMAA): 15% TRIS; gel 5:75% DMAA: 25% TRIS; and gel 6: DMAA) were prepared using a photoinitiation procedure. The gels were incubated in: (1) natamycin dissolved in deionized (DI) water and (2) natamycin encapsulated within Dex-b-PLA NPs in dimethylsulfoxide/DI water. Natamycin release from these materials was monitored using UV-visible spectrophotometry at 304 nm over 7 d. Results: Natamycin uptake by all model CL materials increased between 1 and 7 d (p < 0.001). The uptake of natamycin-NPs was higher than the uptake of the drug alone in DI water (p < 0.05). Drug release was higher in materials containing DMAA than pHEMA (p < 0.05). All gels loaded with natamycin-NPs also released more drug compared to gels soaked with natamycin in DI water (p < 0.001). After 1 h, CL materials loaded with natamycin alone released 28-82% of the total drug release. With the exception of gel 6, this burst released was reduced to 21-54% for CL materials loaded with natamycin-NPs. Conclusions: Model CL materials loaded with natamycin-Dex-b-PLA NPs were able to release natamycin for up to 12 h under infinite sink conditions. DMAA-TRIS materials may be more suitable for drug delivery of natamycin due to the higher drug release observed with these materials. © 2013 Taylor & Francis.

Phan,CM, Hui,A., Subbaraman,L., Jones,L. Insights to Using Contact Lenses for Drug Delivery. Clin Exp Pharmacol 2014;3,145:2161-1459. [ Show Abstract ]

There has been considerable interest in the potential application of contact lenses for ocular drug delivery. This short communication provides an overview of the challenges faced by delivering drugs using contact lenses, highlights the solutions to limitations that have already been achieved, and describes the barriers that remain before commercial application can be realized.

Samsom,M., Chan,A., Iwabuchi,Y., Subbaraman,L., Jones,L., Schmidt,TA In vitro friction testing of contact lenses and human ocular tissues: Effect of proteoglycan 4 (PRG4). Tribology International 2014.

Verma,M. S., Chen,P. Z., Jones,L., Gu,F. X. "Chemical nose" for the visual identification of emerging ocular pathogens using gold nanostars. Biosensors and Bioelectronics 2014;61386-390. [ Show Abstract ]

Ocular pathogens can cause serious damages in the eye leading to severe vision loss and even blindness if left untreated. Identification of pathogens is crucial for administering the appropriate antibiotics in order to gain effective control over ocular infection. Herein, we report a gold nanostar based "chemical nose" for visually identifying ocular pathogens. Using a spectrophotometer and nanostars of different sizes and degrees of branching, we show that the "chemical nose" is capable of identifying the following clinically relevant ocular pathogens with an accuracy of 99%: S. aureus, A. xylosoxidans, D. acidovorans and S. maltophilia. The differential colorimetric response is due to electrostatic aggregation of cationic gold nanostars around bacteria without the use of biomolecule ligands such as aptamers or antibodies. Transmission electron microscopy confirms that the number of gold nanostars aggregated around each bacterium correlates closely with the colorimetric response. Thus, gold nanostars serve as a promising platform for rapid visual identification of ocular pathogens with application in point-of-care diagnostics. © 2014 Elsevier B.V.

Verma,M. S., Chen,P. Z., Jones,L., Gu,F. X. Branching and size of CTAB-coated gold nanostars control the colorimetric detection of bacteria. RSC Advances 2014;4,21:10660-10668. [ Show Abstract ]

Rapid detection of pathogenic bacteria is challenging because conventional methods require long incubation times. Nanoparticles have the potential to detect pathogens before they can cause an infection. Gold nanostars have recently been used for colorimetric biosensors but they typically require surface modification with antibodies or aptamers for cellular detection. Here, CTAB-coated gold nanostars have been used to rapidly (<5 min) detect infective doses of a model Gram-positive pathogen Staphylococcus aureus by an instrument-free colorimetric method. Varying the amounts of gold nanoseed precursor and surfactant can tune the size and degree of branching of gold nanostars as studied here by transmission electron microscopy. The size and morphology of gold nanostars determine the degree and rate of color change in the presence of S. aureus. The optimal formulation achieved maximum color contrast in the presence of S. aureus and produced a selective response in comparison to polystyrene microparticles and liposomes. These gold nanostars were characterized using UV-Visible spectroscopy to monitor changes in their surface plasmon resonance peaks. The visual color change was also quantified over time by measuring the RGB components of the pixels in the digital images of gold nanostar solutions. CTAB-coated gold nanostars serve as a promising material for simple and rapid detection of pathogens. © 2014 The Royal Society of Chemistry.