Latest applications of 3D ToF-SIMS bio-imaging.

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a rapidly developing technique for the characterization of a wide range of materials. Recently, advances in instrumentation and sample preparation approaches have provided the ability to perform 3D molecular imaging experiments. Polyatomic ion beams, such as C60, and gas cluster ion beams, often Arn (n = 500-4000), substantially reduce the subsurface damage accumulation associated with continued bombardment of organic samples with atomic beams. In this review, the capabilities of the technique are discussed and examples of the 3D imaging approach for the analysis of model membrane systems, plant single cell, and tissue samples are presented. Ongoing challenges for 3D ToF-SIMS imaging are also discussed along with recent developments that might offer improved 3D imaging prospects in the near future.

Why is SIMS underused in chemical and biological analysis? Challenges and opportunities.

Improvements have led to many developments in SIMS, including better 2D MS imaging, the ability to perform molecular depth profiling, and the development of 3D MS imaging. (To listen to a podcast about this feature, please go to the Analytical Chemistry website at pubs.acs.org/ac.).

SIMS of biomineralized tissues: present trends and potentials.

The technique of dynamic secondary ion mass spectrometry (SIMS) has, during the 1980s, become a firmly established tool in the microanalytical and microstructural characterization of dental hard tissues. SIMS has proved to be outstandingly suited for charting the distributions of most elements, even at extremely low concentrations, in tooth and bone materials. In-depth concentration profiles as well as surface distribution maps of elements have been recorded with excellent (sub-micron) morphologic resolution. In spite of documented success, only relatively few teams, in a handful of countries, are presently engaged, to any significant extent, in conducting tooth or bone research by the application of SIMS. For dental-medical-surgical laboratories, a partial reason for non-communication is a lack of information about SIMS and its particular assets. Another reason may be connected with an essentially groundless reputation, among non-specialists, of SIMS being an exclusive and expensive technique. Among SIMS laboratories, on the other hand, the inertia in tackling biomineralization is partly due to some particular artifacts of analysis, hitherto not generally known and controlled. The present paper briefly sketches the chief principles of modern SIMS, emphasizing factors of special relevance in the characterization of biomineralized tissues. Examples of recent applications are provided. Present procedures and their limitations are discussed, especially with regard to elemental quantification and imaging. Suggestions for relatively simple modifications to existing routines are offered with the aim of enhancing the ease and availability of SIMS in odontological and surgical research.

Recent developments in medical applications of SIMS microscopy.

The purpose of this review is to present the recent developments in the medical applications of SIMS microscopy. This technique is one of the microanalytical mass spectrometry methods which allow in theory the detection of all the elements of the Mendeleiev table as well as the separation of stable and radioactive isotopes. It is based on a phenomenon whereby a biological sample surface is sputtered by bombardment with an energetic 'primary ion' beam. Part of the sputtered matter is ionized and the resulting 'secondary ions' are characteristic of the atomic composition of the analyzed area. These secondary positive or negative ions are collected and separated in a mass spectrometer at low or high mass resolution, which is dependent on both the element studied and its concentration. An analytic image which conserves the tissue distribution of the selected element is displayed on a fluorescent screen linked to an image processing system. Local elemental concentration can also be measured. Results are highly dependent on the techniques used for sample preparation which should preserve both the chemical and the structural integrity of the tissue. Further, the ionic images must be correlated with corresponding images of the same areas of the serial sections observed in a photonic microscope. With our SIMS microscope (lateral resolution approximately 0.5 microns, and mass resolution 300 to 12,000) we have demonstrated that this microscopic imaging technique is suitable for physiopathological studies. We revisited thyroid iodine metabolism by mapping chemical elements such as 32S and 127I, characteristic of hormonal physiology. Newly organified iodine (radioiodine) can be evaluated in relation to previously stored iodine (127I) in a given follicle, thus allowing an appraisal of glandular adaptation to aging and iodine overload. Another area in which SIMS can be used in medicine, is for the localization of drug markers in tumor tissue (e.g. fluorine-5-fluouracil, iodine in iododeoxyrubicin). This could facilitate the evaluation of the intratumor drug concentration at the onset of the treatment. Likewise, SIMS can be used to localize radiopharmaceuticals used in diagnosis (e.g. technetium) and therapy (131I of metaiodobenzylguanidine). This would permit a better evaluation of the radiation dose delivered to tissue. Further prospects are within reach with the imminent advent of higher lateral resolution (0.05 microns) SIMS microscopes.