Use of Spectroscopic Techniques for Evaluating the Coupling of Porphyrins on Biocompatible Nanoparticles. A Potential System for Photodynamics, Theranostics, and Nanodrug Delivery Applications

Modern medicine has been searching for new and more efficient strategies for diagnostics and therapeutics applications. Considering this, porphyrin molecules have received great interest for applications in photodiagnostics and phototherapies, even as magnetic nanoparticles for drug-delivery systems and magnetic-hyperthermia therapy. Aiming to obtain a multifunctional system, which combines diagnostics with therapeutic functions on the same platform, the present study employed UV/vis absorption and fluorescence spectroscopies to evaluate the interaction between meso-tetrakis(p-sulfonatofenyl)porphyrin (TPPS) and maghemite nanoparticles (γ-Fe₂O₃). These spectroscopic techniques allowed us to describe the dynamics of coupling porphyrins on nanoparticles and estimate the number of 21 porphyrins per nanoparticle. Also, the binding parameters, such as the association constants (K_a = 8.89 × 10⁵ M^-1) and bimolecular quenching rate constant (k_q = 2.54 × 10¹⁴ M^-1 s^-1) were obtained. These results suggest a static quenching process where the electrostatic attraction plays an essential role. The work shows that spectroscopic techniques are powerful tools to evaluate the coupling of organic molecules and nanoparticles. Besides, the system studied provides a relevant background for potential applications in bionanotechnology and nanomedicine, such as (1) nanodrug delivery system, (2) photodiagnostics/theranostics, and/or (3) a combined action of photodynamic and hyperthermia therapies, working in a synergetic way.

Urinary albumin excretion in patients with systemic lupus erythematosus without renal disease

OBJECTIVES

To investigate the prevalence of microalbuminuria, urinary albumin excretion (UAE) between 20-200 micrograms/min, in systemic lupus erythematosus (SLE) patients without clinical renal disease, and to discover if this could predict the development of renal disease.

METHODS

This study made six monthly measurements of UAE, creatinine clearance, serological and clinical data in 22 ambulatory women patients with SLE, without clinical renal disease, hypertension, diabetes or heart failure. The patients were followed up for a period of 18 months (four measurements). Age and sex matched healthy controls were used as a comparative group. UAE was measured by nephelometry in three timed overnight urine samples at each visit.

RESULTS

There were no significant differences in the creatinine clearance between the control group and the SLE patients. Creatinine clearance did not show significant changes throughout the study period. SLE patients had wide variations in the UAE rate compared with healthy controls. In five patients (5 of 22; 23%), on occasions, there was mild, transient increase in UAE reaching the level of microalbuminuria. During follow up, one patient with basal (4.67 micrograms/min) and six month (4.73 micrograms/min) normal UAE rate, was admitted with a nephrotic syndrome confirmed on biopsy examination to be proliferative lupus nephritis. Six months after beginning treatment with prednisone and cyclophosphamide her UAE rate returned to normal values (4.65 micrograms/min).

CONCLUSION

SLE patients without clinical renal disease may have microalbuminuria, although this does not seem to warrant any specific action.