Functional Inorganic Biomaterials for Molecular Sensing and Biomedical Applications

Inorganic biomaterials comprise a broad array of materials that include metals, polymers, ceramics, and composites [1,2,3,4,5,6], and play a pivotal role across disciplines such as chemistry, materials science, biology, medicine [7], and biomedical engineering [8,9,10,11,12,13,14]. The development of inorganic biomaterials with tunable intrinsic properties [15,16] and functionality has positioned them at the forefront of applications from biosensing and imaging [17,18] to therapy [19,20] regenerative medicine, and wound healing [21,22,23,24,25,26,27,28]. The field of tissue engineering and regenerative medicine can vastly benefit from advancements in nanoscience and technology [29,30,31,32], particularly in the fabrication and application of inorganic-based nanoparticles and bioactive materials [1,33,34,35]. Techniques like small-angle X-rays and neutron scattering and light scattering have enabled the structural characterization (size, shape and morphological transitions) of nanostructured biomaterials in the sub-millisecond time scale [36]. Coupled with traditional characterization techniques, scattering methods can facilitate their design and application in advanced bio-nanotechnological fields and disease therapy [36,37]. Mitić et al. [38] reviewed recent developments in the application of instrumental techniques for structural and physicochemical characterization of biomaterials and bone tissue. The same study discussed the application of instrumental techniques, namely, X-ray, IR and Raman vibrational spectroscopy, NMR, ESR, mass spectrometry, atomic absorption spectrometry, inductively coupled plasma-atomic emission spectrometry, thermogravimetric analysis, differential thermal analysis, SEM, and high-resolution TEM, for structural and morphological characterization, and predicting the reactivity, thermodynamic stability, crystalline behavior, and phase transformations of biomaterials.

The Special Issue combines original research and critical reviews that showcase the versatility of inorganic biomaterials and nanoparticles in molecular sensing, targeted therapy [39,40], drug delivery [24], and regenerative medicine [41] utilizing current state-of-the-art techniques [41,42]. The synergy between experiment and computation that is evident throughout the collection highlights the integrative approaches essential in developing next-generation biomaterials.

The study by Cuperová et al. [43] investigated the effect of severe plastic deformation on the microstructure and mechanical properties of an as-cast Zn–0.1 wt.% Mg alloy using the Equal Channel Angular Pressing (ECAP) technique. Zn-based alloys showed strong potential as bioactive materials for intracorporeal implants due to their lower cytotoxicity, reduced inflammatory responses compared to pure Zn, and improved biocompatibility and optimal degradation rate in physiological environments. This study underscored ECAP’s effectiveness in simultaneously enhancing strength and ductility in Zn-based alloys, thereby advancing their potential applications as orthopedic implant materials.

The synthesis of a novel silver(I) complex, [Ag(HL¹)₂]NO₃ (AgHL¹), with a coumarin derivative, (3E)-3-(1-{[(pyridin-2-yl)methyl]amino} ethylidene)-3,4-dihydro-2H-benzopyran-2,4-dione (HL¹) was reported Kurjan et al. [44] to study their anticancer and antimicrobial activity. The HL¹ ligand exhibited moderate activity, while AgHL¹ displayed a pronounced, time- and dose-dependent inhibitory effect on the metabolic activities of both cancerous cell lines. The flexural strength, color change and antimicrobial effect of silver–zeolite NPs in acrylic resin materials was reported by Yaman et al. [45] using three different rates of NPs (0%, 2%, 4%, 5%). Discs with 2% silver–zeolite NPs showed a significant antimicrobial effect and were more effective against C. albicans than those with rates of 4% and 5%. While adding silver–zeolite NPs provided antimicrobial properties, it reduced the material’s structural integrity and altered its esthetic appearance, highlighting the necessity of balancing antimicrobial efficacy with mechanical and esthetic properties in dental materials.

Marabello et al. [46], employed a computational method to investigate three new solid salicylatoborate compounds, [Ca(H₂O)₆](C₁₄H₈O₆B)₂ (CaSB), [Cu(C₁₄H₈O₆B)] (CuSB), and [Li(C₁₄H₈O₆B)(H₂O)] (LiSB), as potential boron and/or lithium delivery agents for the development of ¹⁰B-enriched NPs in neutron capture therapy (NCT). LiSB exhibited the highest dose absorbed by the tumor mass and resulted in being the most efficient compound. Thus, to design more efficient compounds for NCT, the density of ¹⁰B should be enhanced rather than that of ⁶Li.

Doxorubicin (DOX)-loaded Ca-Mg-doped mesoporous silica nanoparticles (MSNs) were developed by Zhang et al. [47] as tumor-targeted drug delivery systems for breast cancer. The incorporation of calcium and magnesium demonstrated an increase in the degradation rate under acidic conditions and an accelerated release, which reduced the toxicity of DOX and promoted cellular uptake. Molecular dynamic simulation was used to study the intermolecular interactions and physicochemical properties of novel mesoporous silica. Doping with calcium and magnesium led to an increase in the free energy of the system; the free energy of the Ca₂Mg₂@MSNs group was the largest, which indicated that the stability of the MSN system decreased after being doped with calcium and magnesium. Hemolysis experiments verified that MSNs could be used as a carrier for medical purposes. Liu et al. [48] synthesized multifunctional Ca²⁺ doped mesoporous silica nanoparticles (CMSNs) using the sol–gel method. DOX was loaded into the as-prepared CMSNs (CMSNs@Dox). The doping of Ca²⁺ endowed the MSNs with the ability to carry out excellent specific degradation and pH-responsive drug release, and enabled the synergy of chemotherapy and calcicoptosis. This newly prepared Ca²⁺-doped nanoplatform provided a practical and feasible strategy for improving the efficacy of chemotherapy.

Barnash et al. [49] studied the effect of CoFe₂O₄ NPs on the properties of an electro-optical liquid crystal (LC) cell based on the nematic composition of 4-Cyano-4′-pentylbiphenyl (5CB). At the input signal, with a frequency of 500 kHz, a resonant current increase was obtained in the electrical circuit, followed by a decrease in the current with an increase in the frequency. An increase in the resonant current caused a decrease in LC cell impedance. This indicated the formation of a consistent oscillatory circuit. Giacomet et al. [50] developed a simple and cheap electrochemical method for diagnosing antibodies against SARS-Cov-2. Disposable screen-printed carbon electrodes (SPEs) covered with gold microblobs (AuMBs) were synthesized. The SPE-AuMBs were coated with cysteamine, which allowed the N-hydroxysuccinimide-activated SARS-CoV-2 antigen to be immobilized. The antigen-activated SPE could qualitatively and quantitatively evaluate the presence of SARS-CoV-2 antibodies. The antibody analysis took around 15 min and was cheaper than traditional rapid tests.

Ntoupis et al. [51] measured the luminescence efficiency of a cerium fluoride (CeF₃) inorganic scintillator in crystal form as a possible alternative to high-luminescence but hygroscopic cerium bromide (CeBr₃). The obtained luminescence efficiency results showed that CeF₃ was not suitable for medical imaging applications covering the range of 50–140 kVp; however, an examination of its luminescence output in the nuclear medicine energy range (~70 to 511 keV) could reveal possible applicability in these modalities. Lastly, Saikia [33] reviewed the emerging applications of inorganic-based NPs and biomaterials in stem cell regenerative research, tissue engineering, artificial skin and cartilage regeneration, neural nerve injuries, 3D bioprinting, and the development of novel bio-scaffolds. The review also addressed critical challenges in the clinical application of inorganic biomaterials in regenerative medicine such as their biocompatibility and bioaccumulation, toxicity, assessment tools, optimization of mechanical properties, and their long-term fate.

The contributions in the Special Issue range from advanced molecular sensing to innovative therapeutic strategies for the treatment of diseases, and bridge the interfaces between chemistry, biology, engineering, and medicine. My hope is that this Special Issue collection, Functional Inorganic Biomaterials for Molecular Sensing and Biomedical Applications, will not only stimulate ongoing research advancements in the field but also inspire interdisciplinary collaborative efforts aimed at translating fundamental research into real-world applications. I take this opportunity to invite researchers to contribute to the second volume of the Special Issue, Functional Inorganic Biomaterials for Molecular Sensing and Biomedical Applications, 2nd Edition, that will continue to focus on recent advances in inorganic biomaterials and nanoparticles. The forthcoming volume includes all stages of the process, from rational design and structural characterization to applications in molecular sensing, clinical diagnosis, drug delivery, and medicine.