**1. Introduction**

Cancer is one of the most common and serious diseases currently, considered a public health problem [1–3]. The prostate cancer, according to INCA, is the most accessible in men in Brazil and difficult diagnoses for slow development and absence of signaling in the early stages of the disease, and can progress to more advanced stages with metastasis. The success in treatment depend on the extent of cancer at the time of diagnosis and, thus, nanotechnology can be a tool to improve diagnostic technique and for improve the quality of treatments [4–10].

preventing the action of antibiotics [32–36]. In order to reduce microbial adhesion, several researchers have been studying nanocrystals with antimicrobial properties as a promising tool to control microbial adhesion, since nanocrystals with catalytic properties have the

Biocompatibility of Doped Semiconductors Nanocrystals and Nanocomposites

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Therefore, in the book chapter we investigated the cytotoxicity of Ag or Ca doped ZnO NCs in normal and tumor cells, as well as, the viability of ZnO doped with Ag, Eu, Ni and your

The development of nanoparticles for medical purposes has been widely investigated, since when the size is greatly reduced at the nanometric scale, the reason surface/volume increase generating new and interesting properties, such as a greater ability to absorb drugs, probes and proteins [41] In addition to size and shape, a crystalline nanoparticle (NPs) alters as both physical and biological properties. For example, Spanó et al. have shown that amorphous nanoparticles are more genotoxic than crystalline (nanocrystals) [42]. In addition, a crystal phase in which nanocrystals (NCs) themselves also enables physical and biological properties [43].

The use of nanoparticles and nanocrystals as novel therapeutic antimicrobial agents have been described some of the metallic compounds possess antimicrobial property especially inorganic metal oxides [44]. Moreover, the alliance of nanotechnology and biology has brought to

Several types of nanocrystals have been synthesized in order to obtain an efficient nanomaterial. However, it is important to emphasize that nanocrystals must be biocompatible and specific [45]. Based on this and knowing that zinc oxide nanocrystals (ZnO) are biocompatible materials, according to the US Food and Drug Administration (FDA), in this chapter we

Nanocrystals of zinc oxide (ZnO) exhibit many important characteristics, such as high catalytic activity, chemical and physical stability, as well as ultraviolet (UV) absorption [46, 47]. The technique most used to produce defects aiming to increase the catalytic activity in ZnO nanocrystals is based on the choice of synthesis methods [34], use of nanocomposite photo-

ZnO nanocrystals have the unique ability to induce oxidative stress in cancer cells and bacteria, being one of the main mechanisms of cytotoxicity and bactericidal action [32, 50, 51]. This property is due to the semiconductor nature of ZnO, which induces the generation of reactive oxygen species (ROS), leading to oxidative stress and cell death or bacteria [52–54]. Another type of nanocrystalline that enters the category of biocompatible is nickel because it is a basic element that is part of metalloproteins, being vital for living beings. Nickel (Ni), silver (Ag) and calcium (Ca) nanocrystals and oxide have several advantages as antimicrobial

**2. Doped semiconductors nanocrystals and nanocomposites**

fore metals in the form of nanoparticles as potential antimicrobial agents.

potential to reduce biofilm formation [32, 35, 37–40].

nanocomposites against microorganisms.

investigated this nanocrystal.

and antitumor agents [55–57].

catalysts [48], and doping with impurities [49].

Breast cancer is considered as a heterogeneous disease in its pathological characteristics. The follow-up of the disease is quite complex, mainly due to the existence of the various tumor subtypes, which have different expression profile, therapeutic response and clinical behavior [4, 11–15]. The molecular classification divides breast cancers into many groups, based on molecular expression profile. Triple negative breast cancer (TNBC), characterized by lack of expression of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor type 2 (HER2), comprises the highest invasive potential and worst clinical outcome [16, 17]. In addition, this breast cancer presents survival rates significantly lower and recurrence rates significantly higher compared to other breast cancer subtypes [17–19]. Moreover, the identification of specific targeted therapy and improved diagnosis for TNBC is fundamental.

In the last decades, cancer has been presenting itself as a health problem public interest, raising the urgent interest in research for the development of drugs with antitumor activity. Nanotechnology has been a tool for development of new nanoparticles with antineoplastic properties [5, 20–23].

In recent years, with the emergence of certain biomedical problems, such as increased infections of pathogenic strains resistant to antimicrobials and the development of new cancers, the development of new effective tools has been extremely important. Therefore, the use of nanotechnology is important, since depending on the size and shape of nanocrystals it is possible to control their physical and chemical properties [24, 25].

The concern about pathogens and multi-drug microorganisms in food, veterinary and medical industry are boosting the demand for new antimicrobial substances. Since a large number of microorganisms have showed resistance against different antibiotics, the potential antimicrobial substance should be able to destroy or inhibit these microorganisms in different matrices and do not promote resistance [26–29]. Moreover, this compound should be cheap, easy to use, bacteria specific and non-toxicity to the human or animals.

Pathogenic microbial contamination and eradication of organic pollutants have been a major threat to mankind and the environment. Therefore, the development of new, more efficient materials with improved photocatalytic and antimicrobial activity is of great importance.

The increase in bacterial resistance towards conventional antibiotics generally occurs because some bacteria form slime which facilitates adhesion and formation of biofilms on any surface or implantable devices [30, 31]. Thus, the formation of biofilms increases bacterial resistance, preventing the action of antibiotics [32–36]. In order to reduce microbial adhesion, several researchers have been studying nanocrystals with antimicrobial properties as a promising tool to control microbial adhesion, since nanocrystals with catalytic properties have the potential to reduce biofilm formation [32, 35, 37–40].

Therefore, in the book chapter we investigated the cytotoxicity of Ag or Ca doped ZnO NCs in normal and tumor cells, as well as, the viability of ZnO doped with Ag, Eu, Ni and your nanocomposites against microorganisms.
