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In this contribution, we would like to underline the peculiar chemical properties of nanometer scale metallic particles. To attain this goal, we select the case of DeNox catalysis (NOx reduction to nitrogen molecule) for which such nanomaterials play a crucial role. Experimental data as well as recent theoretical calculation through density functional theory are used to assess the relationship between the adsorption mode of NO and the behaviour of nanometre scale metallic particles.

Most papers on kidney stones arising from infection concentrate on the mineral struvite. In this contribution, we would like to call attention to other mineral phases such as highly carbonated calcium phosphate apatite, ammonium urate, and whitlockite, by presenting clinical and chemical data. We start with epidemiological data which emphasize the increase in the prevalence of kidney stones related to infection. Then we present a statistical analysis of more than 85,000 stones which have been analysed at the Laboratoire des Lithiases of Assistance Publique-Hôpitaux de Paris which gives insights regarding the link between urinary tract infection and struvite, carbonated calcium phosphate apatite (carbapatite), and also surprisingly whitlockite. Some information regarding the pathogenesis of kidney stones linked to infection, the nature of the bacteria which have been identified, and the approach to precisely analyse infrared spectra to identify struvite, carbapatite, and whitlockite, conclude this first part. To complete this clinical description, we describe the crystallographic structure and the chemistry of three relevant compounds namely carbonated calcium phosphate, struvite, and whitlockite. To conclude this second part, the dependence of crystallite morphology of struvite on pH and on the presence, or absence, of bacteria, is described. Based on clinical and chemical data, it is becoming clear that struvite is not the only mineral intimately related to renal infectious processes, but that whitlockite and carbapatite with a high carbonation rate are strongly associated with urinary tract infection as well.

X-ray Photoelectron Spectroscopy (XPS) constitutes an elegant way to describe the chemical characteristics of the surface of biological materials. It is thus a unique approach to decipher the interaction between biological materials and tissues. In the case of medical implants, it is thus possible to understand its biocompatibility as well as its integration in the body which can be wanted in the case of prothesis or avoided in the case of JJ-stents. More precisely, XPS can bring valuable information of the interaction between physiological calcification (here bone) and the prosthesis as well as the interaction between pathological calcifications (lithiasis) and the JJ-stent. This mini overview is dedicated to two communities, the physical chemists and the clinicians. In the first part of this overview, after an introduction on the basic principles of XPS, we focus on the theoretical techniques adopted for the computation of XPS spectra of materials.The second part, dedicated to clinicians, describes the use of XPS for the characterization of biological materials. We report which kind of chemical information can be gained by this surface-sensitive technique and how this information has a relevant impact on medical applications.Through different examples, we show that XPS is a strong and very useful tool, and thus receiving a crucial place in medical research.

Medical literature indicates clearly that cystinuria and cystinosis, two severe genetic pathologies, are related to the presence of abnormal L-cystine deposits. While L-cystine adopts a hexagonal crystal morphology consistent with its crystallographic structure (hexagonal, $\mathrm{P}6_{1}22$ space group), abnormal deposits related to cystinosis display a rectangular shape. Because this is unexpected from the hexagonal crystallographic structure of L-cystine, we have investigated this inconsistency using SEM (scanning electron microscopy) and IR (infrared) spectroscopy at micrometre and nanometre scales. Our data clearly indicate the presence of both L-cysteine and L-cystine. Considering that L-cysteine crystals display a rectangular shape, and that a transition phase between L-cysteine and L-cystine is well known, we propose the following model for deposit evolution in cystinosis. The initial abnormal deposit consists of L-cysteine, with a rectangular crystal morphology. The micrometre scale rectangular crystallite shape is retained after the phase transition equilibrium between L-cysteine and L-cystine is established, with some crystalline L-cysteine still remaining.

Since its first use several decades ago, scanning electron microscopy has been used in numerous investigations dedicated to biological systems. This contribution focuses on observations on pathological calcifications in order to review several major applications of primary importance to the clinician. Among these, we highlight such observations as medical diagnostic tools in pathologies arising from primary hyperoxaluria and urinary infections.

Density Functional Theory has made the study of biomaterials feasible in the past years leading to better understanding of causes and possible treatments of related pathologies. Although it has been successfully applied in many fields, it has not yet consistently found its way into the field of pathological calcifications. An overview will be given of the studies where this technique has been applied in order to outline the important contributions that it can bring in the field of biomineralization. More specifically, studies on DFT calcifications from calcium oxalates and calcium phosphates, with relevance to bone formation and kidney stones, will be reviewed. Finally, a short outlook on silica mineralization will be presented as well.

In this contribution dedicated to kidney stones containing Whitlockite (Wk), we addressed three questions, namely, the presence of iron in Wk, the relationship between bacterial imprints and the presence of Wk, and finally the relationship between the crystal size of Wk-bearing stones and infection. The complete dataset indicates that iron is not present in our Wk stoichiometry. We also note the presence of bacterial imprints for kidney stones with a high, but sometimes a low content, of Wk. Finally, we propose FE-SEM as a diagnostic tool for stone patients who have a negative urine culture associated with kidney stones containing less than 20% by weight Wk, a low level of carbonate in apatite, and no struvite. Such a diagnostic tool would represent a significant benefit to the clinician.