A series of pH and GSH responsive photosensitizers were designed and synthesized. pK a values were optimized by adjusting the inductive contribution of substituents to reach a pH range (6.0-7.4) relevant to the tumour microenvironment. pH-Activatable behaviour and redox mediated release of the quencher from the PS by GSH allow the construction of an AND logic operator for selective photodynamic action in aqueous solutions.The research in molecular logic gates, which was initiated by the seminal work by de Silva, 1 blossomed in the two decades that followed. 2 In addition, the limitations and the potential of this approach has become more clear. A particularly promising application of molecular logic gates may be in the field of information processing therapeutic agents. Incorporation of Boolean logic ideas in the function of therapeutic agents would be very valuable, if the same results cannot be achieved by random optimization studies. Previously, our group and others provided the early examples of the work in that direction. 3 Our first proof of principle work which linked photodynamic sensitization of a Bodipy based photosensitizer (PS) to the concentrations of sodium ions and the acidity was essentially an AND logic gate, but the system required organic solvents and organic acid to function in the desired manner. While it was considered to be noteworthy for that approach to have practical potential, an AND logic gate based enhanced selectivity should be related to cancer related biological parameters, which can generate significant changes in the photophysical character of the sensitizer in aqueous solutions.In this work, we took advantage of two characteristics of the tumour microenvironment, lower pH and higher glutathione concentrations. 4 The difference in pH between cancer tissue and healthy tissue is an easily accessible parameter for use in therapeutic activation. A number of pH-responsive polymeric materials, photosensitizers, and nanocarriers were studied to control drug release or activation. 5 However, extracellular pH of tumor cells drops to a value not below 6.0. 6 Thus, it is challenging to find a smart therapeutic system responsive to pH within the narrow near neutral range and essentially become active at around pH 6.0-6.5 and stay inactive above pH 7.0. Apart from some, 7 most related studies in the literature depend on activation at pH below 5.5, which actually requires nonselective lysosomal activation. 8 In this work, the properties of the PS are optimized for pH activatability by causing rational chemical modification on the pH responsive moiety with electron donating or withdrawing groups to adjust the pK a to the desired near-neutral value and to get enough spectral shift in acidic aqueous solutions such that protonated PSs are exclusively excited species under the conditions of interest. Thus, the overall design (Scheme 1) involves a pH responsive unit, linked to a quencher, which could be cleaved at elevated GSH concentrations. Previously, GSH has been used as a PS activator mostly t...

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The binding and release of trivalent rare earth element (REE) cations (Dy(3+), Nd(3+) and La(3+)) from solutions by a new fully characterized magnetic nano adsorbent material, consisting of iminodiacetic acid ligand (H2IDA) grafted onto SiO2 covered γ-Fe2O3 nanoparticles, was investigated. The nano adsorbent revealed a slightly higher capacity towards heavier REE and appreciable selectivity, especially on desorption. It was found that the composition of the surface complex was RE(3+) : L = 1 : 1. The complexation of the molecular H2IDA with RE(3+) in this ratio under non-basic conditions was therefore investigated by X-ray crystallography to produce relevant molecular models. Unexpectedly big differences in coordination numbers and binding mode of IDA along with distinct analogies in packing of the ligand molecules in the obtained 2D-coordination polymer structures provided valuable insights into possible reasons for the observed selectivity.

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