Magnetic Nanoplatforms for in Situ Modification of Macromolecules: Synthesis, Characterization, and Photoinactivating Power of Cationic Nanoiman–Porphyrin Conjugates

Abstract

A nanoplatform concept was developed to synthesize accessible photoactive magnetic nanoparticles (MNPs) of Fe 3 O 4 coated with silica. This approach was based on the covalent binding of 5,10,15,20-tetrakis-(pentafluorophenyl)porphyrin (TPPF 20 ) to aminopropyl-grafted MNPs by nucleophilic aromatic substitution reaction (S N Ar) to obtain conjugate MNP− P1. After in situ modification, the remaining pentafluorophenyl groups of TPPF 20 attached to MNPs were substituted by dimethylaminoethoxy groups to form MNP−P2. The basic amine group of these conjugates can be protonated in aqueous media. In addition, MNP−P1 and MNP−P2 were intrinsically charged to produce cationic conjugates MNP + −P1 and MNP + −P2 + by methylation. All of them were easily purified by magnetic decantation in high yields. The average size of the MNPs was ∼15 nm, and the main difference between these conjugates was the greater coating with positive charges of MNP + −P2 + , as shown by the zeta potential values. Absorption spectra exhibited the Soret and Q bands characteristic of TPPF 20 linked to MNPs. Furthermore, these conjugates showed red fluorescence emission of porphyrin with quantum yields of 0.011−0.036. The photodynamic effect sensitized by the conjugates indicated the efficient formation of singlet molecular oxygen in different media, reaching quantum yield values of 0.17−0.34 in N,N-dimethylformamide. The photodynamic activity of the conjugates was evaluated to inactivate the Gram-positive bacteria Staphylococcus aureus, the Gram-negative bacteria Escherichia coli, and the yeast Candida albicans. The modified cationic MNP + −P2 + was the most effective conjugate for photodynamic inactivation (PDI) of microorganisms. Binding of this conjugate to bacteria and photoinactivation capability was checked by means of fluorescence microscopy. Also, sustainable use by recycling was determined after three PDI treatments. Therefore, this methodology is a suitable scaffold for the in situ modification of conjugates, and in particular, MNP + −P2 + represents a useful photodynamic active material to eradicate microorganisms.

Latest trends on photodynamic disinfection of Gram-negative bacteria: photosensitizer’s structure and delivery systems

“…This could be addressed, for example, by immobilization of the PS on magnetic iron oxide nanoparticles, which can be visualized and guided in water and organic solvents, by means of an external magnetic field. Besides, magnetic nanoparticles have been widely used for the transport and delivery of drugs, demonstrating their biocompatibility, safety, stability, while also representing, and ecological alternative [112,113] . As a sidenote, for the nanoparticles suspension studies, ζ-potential is the surface charge of the nanoparticle, which determines the behavior of the suspension.…”

Synthesis of Porphyrins with ABAB Symmetry from Dipyrromethanes as Potential Phototherapeutic Agents

“…The pentafluorophenyl group attached at the meso position of the porphyrins 4 and 5 can easily undergo a regiospecific nucleophilic aromatic substitution of the para-fluorine atom by a diverse set of nucleophiles [3,10]. Thus, this substituent was used to covalently link the porphyrin ring to several functionalized structures [4]. In porphyrin 4, N,N-dimethylaminophenyl substituent can be used to obtain cationic intrinsic charge by methylation [5].…”

“…However, depending on the substituents on the periphery of the tetrapyrrolic macrocycle, these molecules tend to aggregate, producing a loss of photodynamic activity. Thus, to achieve effective photoinactivation, these compounds can bind to different supports forming photoactive materials [3,4]. In this sense, it is interesting to develop porphyrins asymmetrically substituted in the meso positions by two different structures (A and B).…”

Functionalization of Magnetic Nanoparticles with Organic Ligands toward Biomedical Applications

“…Numerous techniques have been reported for surface modification of MNPs, including ligand replacement, [ 30 ] self‐assembly, [ 31 ] and in situ synthesis, [ 32 ] which can not only integrate functions and components of organic ligands and MNPs but also offer promising tools to tailor their properties for biomedical applications. This review starts by introducing various organic ligands that are used for surface engineering of MNPs.…”

“…In addition, various tumor microenvironment-responsive polymers have been widely developed and applied to drive MNP self-assembly into smart nanocarriers for drug delivery, controlled release, and enhanced MR contrast in desired pathological regions. [29] Numerous techniques have been reported for surface modification of MNPs, including ligand replacement, [30] self-assembly, [31] and in situ synthesis, [32] which can not only integrate functions and components of organic ligands and MNPs but also offer promising tools to tailor their properties for biomedical applications. This review starts by introducing various organic ligands that are used for surface engineering of MNPs.…”