« RAMAN
these studies, with the nanoparticles localizing at the gastrointestinal mucous layer and blood brain barrier increasing the transport of the peptide across the respective barrier membranes.
The intracellular distribution of drugs is also of great interest, and can be used to probe the mechanisms of drug action, or lack thereof. TPEF has been used to track the fate of doxorubicin in cells, with drug resistant cells showing a decreased drug accumulation in the cell nucleus [33]. The cell-by-cell nature of the analysis has allowed variability in such accumulation between cells for the same strain to be probed [34]. Detecting the fate of non-fl uorescing free drug molecules without labels using CARS or SRS is still a challenge due to lack of sensitivity. However, the cellular distribution of nanoparticles may be effi ciently probed using these techniques. Xu et al (2009) have highlighted the potential problems of using fl uorescent dyes or markers for tracking nanoparticles. In their elegant study, the fate of poly(lactic-co-glycolic acid) (PLGA) nanoparticles incubated with carcinoma cells was determined. Results from fl uorescent imaging of PLGA nanoparticles loaded with Nile red dye suggested the nanoparticles were internalized by the cells. However, by directly detecting the PLGA using CARS microscopy, it was revealed that the nanoparticle did not enter the cells but instead were localized on the cell membrane surface. The Nile red dissociated from the nanoparticle before entering the cell. This research also highlighted the importance of localization eff ects with contact between drug loaded nanoparticles
and the cell membrane likely to be facilitating drug uptake, possibly through increased localized concentration of the drug at the cell membrane surface [38].
Conclusions
The applications described above demonstrate the diverse potential of various forms of nonlinear optical imaging in pharmaceutical analysis. With chemical and structural information able to be obtained at high spatial and temporal resolutions, new insights, which are either impossible or less convenient to obtain with comparable established imaging techniques, (e.g. Raman mapping), may be obtained. The setups involved with CARS and SRS microscopes generally also allow TPEF and SHG imaging on the same samples which increases the analytical power. Potential limitations are often sample specifi c, and may include a lack of sensitivity with low sample concentrations, lack of specifi city for structurally similar materials, and sample burning. The development of the technology, including improved specifi city (e.g. with hyperspectral developments) and sensitivity (with optimized sources and modes of detection), while simultaneously optimizing imaging speed, is a very active research fi eld. With the increasing availability and capability of nonlinear optical microscopes, especially those capable of CARS and SRS imaging, their use in increasingly
Raman ork t i n Raman Analyzer for Research
W AT Technology (mm)
• Video Capture & Image Overlay • Robust, Reliable, Reproducible Raman • Qualitative & Quantitative Analysis
Sato
785 nm – 1 wavelength, 1 Instrument Transmission to Millimeters to Microns • Raman Microscopy & Imaging • Transmission Raman (Variable Spot size) • Ph
tm
COMPLIMENTARY Register for Kaiser’s Customer Presented Raman Webinars, or View a Webinar Archive. Go to:
www.kosi.com/webinars/
HTS Screening
Ph
AST Map
Transmission / Backscatter
Versatile Instrumentation • Remote Probe Options • Immersion or Non-Contact Sampling
www.americanpharmaceuticalreview.com |
| 61
»
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154 |
Page 155 |
Page 156