In recent years miscellaneous smart micro/nanosystems that respond to various exogenous/endogenous stimuli including temperature, magnetic/electric field, mechanical force, ultrasound/light irradiation, redox potentials, and biomolecule concentration have been developed for targeted delivery and release of encapsulated therapeutic agents such as drugs, genes, proteins, and metal ions specifically at their required site of action. Owing to physiological differences between malignant and normal cells, or between tumors and normal tissues, pH-sensitive nanosystems represent promising smart delivery vehicles for transport and delivery of anticancer agents. Furthermore, pH-sensitive systems possess applications in delivery of metal ions and biomolecules such as proteins, insulin, etc., as well as co-delivery of cargos, dual pH-sensitive nanocarriers, dual/multi stimuli-responsive nanosystems, and even in the search for new solutions for therapy of diseases such as Alzheimer’s. In order to design an optimized system, it is necessary to understand the various pH-responsive micro/nanoparticles and the different mechanisms of pH-sensitive drug release. This should be accompanied by an assessment of the theoretical and practical challenges in the design and use of these carriers.

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In recent years, using heavy metal compounds such as platinum as anticancer agent is one of the common ways in chemical therapy. In this study, a new anticancer compound of glycine derivatives of Pt(II) complex (amyl-glycine1, 10-phenanthroline Platinum nitrate) was designed, and the biological effects of this novel compound on the alterations in the function and structure of human hemoglobin (Hb) at different temperatures of 25 and 37°C were assessed by applying various spectroscopic (fluorescence and circular dichroism (CD)) and theoretical methods. Fluorescence data indicated the strong ability of Pt(II) complex to quench the intrinsic fluorescence of Hb. The binding constant, number of binding sites, and thermodynamic parameters at two temperatures were calculated, and the results indicated the major possibility of occurring van der Waals force or hydrogen bond interactions in the Pt(II) complex-Hb interaction. For evaluating the alteration of secondary structure of Hb upon interaction with various concentrations of complex, far-UV CD spectra were used and it was observed that in high dose of complex, significant changes were occurred which is indicative of some side effects in overdosing of this complex. On the other hand, the molecular docking results illustrate that are well in agreement in obtaining data with spectroscopy. Above results suggested that using Pt(II) complex as an anticancer agent, model drug in high-dose usage might cause some disordering in structure and function of Hb as well as improve understanding of the side effects of newly designed metal anticancer drugs undergoing.

In the present study, biological evaluation of a new synthesized anti-cancer compound, amyl-glycine1, 10-phenanthroline Platinum nitrate (Pt(II) complex), was investigated at different temperatures by spectroscopic methods (far-UV circular dichroism (CD) and fluorescence) and modeling methods (docking and FRET). Human serum albumin (HSA), one of the vital proteins in drug delivery system in the body, was used as a target protein. The Pt(II) complex is able to quench the intrinsic fluorescence of HSA considerably. Binding and thermodynamic parameters of the interaction between the protein and the ligand were analyzed by fluorescence quenching method. The far-UV CD spectra revealed that the secondary structure of HSA did not show any noticeable change upon interaction with Pt(II) complex at both 25 and 37°C. The calculation of fluorescence resonance energy transfer (FRET) confirmed that quenching mechanism is static, and the observed distance between the donor and acceptor is 1.18 nm. Molecular docking results are in agreement with experimental data suggesting that there is one site on HSA at which Pt(II) complex binds spontaneously. Moreover, docking results together with FRET evaluation illustrated that Pt(II) complex is located near Trp214 at a distance of 1.96 nm. Our experimental and theoretical results indicated that the driving forces for Pt(II) complex interaction with HSA are hydrogen bonding and van der Waals interactions. The combination of molecular docking and spectroscopy methods suggested that use of this new Pt(II) complex as an anti-cancer agent, is an effective innovative approach in cancer chemotherapy providing a better understanding of effects of new designed drugs.

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