New types of contactless luminescence nanothermometers, namely, LiAl₅O₈:Fe³⁺ and LiAl₅O₈:Fe³⁺, Nd³⁺ are presented for the first time, revealing the potential for applications in biological systems. The temperature-sensing capability of the nanocrystals was analyzed in wide range of temperature (−150 to 300 °C). The emission intensity of the Fe³⁺ ions is affected by the change in temperature, which induces quenching of the ⁴T₁ (⁴G) → ⁶A₁ (⁶S) Fe³⁺ transition situated in the 1st biological window. The highest relative sensitivity in the temperature range (0 to 50 °C) was found to be 0.82% °C (at 26 °C) for LiAl₅O₈: 0.05% Fe³⁺ nanoparticles that are characterized by long luminescent lifetime of 5.64 ms. In the range of low and high temperatures the S_max was calculated for LiAl₅O₈:0.5% Fe³⁺ to be 0.92% °C at −100 °C and for LiAl₅O₈:0.01% Fe³⁺ to be 0.79% °C at 150 °C. The cytotoxicity assessment carried out on the LiAl₅O₈:Fe³⁺ nanocrystals, demonstrated that they are biocompatible and may be utilized for in vivo temperature sensing. The ratiometric luminescent nanothermometer, LiAl₅O₈:Fe³⁺, Nd³⁺, which was used as a reference, possesses an S_max = 0.56%/°C at −80 °C, upon separate excitation of Fe³⁺ and Nd³⁺ ions using 266 nm and 808 nm light, respectively.

Herein, a novel synthesis method of colloidal GdPO₄:Mn²⁺,Eu³⁺ nanoparticles for luminescent nanothermometry is proposed. XRD, TEM, DLS, and zeta potential measurements confirmed the crystallographic purity and reproducible morphology of the obtained nanoparticles. The spectroscopic properties of GdPO₄:Mn²⁺,Eu³⁺ with different amounts of Mn²⁺ and Eu³⁺ were analyzed in a physiological temperature range. It was found that GdPO₄:1%Eu³⁺,10%Mn²⁺ nanoparticles revealed extraordinary performance for noncontact temperature sensing with relative sensitivity S_R = 8.88%/°C at 32 °C. Furthermore, the biocompatibility and safety of GdPO₄:15%Mn²⁺,1%Eu³⁺ was confirmed by cytotoxicity studies. These results indicated that colloidal GdPO₄ doped with Mn²⁺ and Eu³⁺ is a very promising candidate as a luminescent nanothermometer for in vitro applications.

Li⁺/Eu³⁺ dual-doped calcium apatite analogues were fabricated using a microwave stimulated hydrothermal technique. XRPD, FT-IR, micro-Raman spectroscopy, TEM and SAED measurements indicated that obtained apatites are single-phased, crystallize with a hexagonal structure, have similar morphology and nanometric size as well as show red luminescence. Lithium effectively modifies the local symmetry of optical active sites and, thus, affects the emission efficiency. Moreover, the hydrodynamic size and surface charge of the nanoparticles have been extensively studied. The protein adsorption (lysozyme, LSZ; bovine serum albumin, BSA) on the nanoparticle surface depended on the type of cationic dopant (Li⁺, Eu³⁺) and anionic group (OH⁻, Cl⁻, F⁻) of the apatite matrix. Interaction with LSZ resulted in a positive zeta potential, and the nanoparticles had the lowest hydrodynamic size in this protein medium. The cytotoxicity assessment was carried out on the human osteosarcoma cell line (U2OS), murine macrophages (J774.E), as well as human red blood cells (RBCs). The studied apatites were not cytotoxic to RBCs and J774.E cells; however, at higher concentrations of nanoparticles, cytotoxicity was observed against the U2OS cell line. No antimicrobial activity was detected against Gram-negative bacteria with one exception for P. aeruginosa treated with Li⁺-doped fluorapatite.

In this research we subjected samples of poly(L-lactide) (PLLA) extruded film to ultraviolet (193 nm ArF excimer laser) radiation below the ablation threshold. The modified film was immersed in Simulated Body Fluid (SBF) at 37 °C for 1 day or 7 days to obtain a layer of apatite ceramic (CaP) coating on the modified PLLA surface. The samples were characterized by means of optical profilometry, which indicated an increase in average roughness (Ra) from 25 nm for the unmodified PLLA to over 580 nm for irradiated PLLA incubated in SBF for 1 day. At the same time, the water contact angle decreased from 78° for neat PLLA to 35° for irradiated PLLA incubated in SBF, which suggests its higher hydrophilicity. The obtained materials were investigated by means of cell response fibroblasts (3T3) and macrophage-like cells (RAW 264.7). Properties of the obtained composites were compared to the unmodified PLLA film as well as to the UV-laser irradiated PLLA. The activation of the PLLA surface by laser irradiation led to a distinct increase in cytotoxicity, while the treatment with SBF and the deposition of apatite ceramic had only a limited preventive effect on this harmful impact and depended on the cell type. Fibroblasts were found to have good tolerance for the irradiated and ceramic-covered PLLA, but macrophages seem to interact with the substrate leading to the release of cytotoxic products.