• Design and Synthesis of a Novel Nanoparticle for Photothermal Therapy
  • Niloofar Mohandesi,1 Ahmad Reza Bahrami ,2 Amir Sh. Saljooghi ,3 Maryam M. Matin,4,*
    1. Department of Biology, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran
    2. Industrial Biotechnology Research Group, Institute of Biotechnology, Ferdowsi University of Mashhad, Mashhad, Iran
    3. Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran
    4. Novel Diagnostics and Therapeutics Research Group, Institute of Biotechnology, Ferdowsi University of Mashhad, Mashhad, Iran


  • Introduction: Cancer remains one of the leading causes of death worldwide. Traditional therapies such as surgery, chemotherapy and radiotherapy have their own limitations, including invasiveness, various side effects, and tumor recurrence. Photothermal therapy (PTT), a form of localized treatment that utilizes nanoparticles to absorb light and generate heat, has emerged as a promising approach for cancer treatment due to its non-invasive nature, high precision, and ability to specifically target tumor cells. The ability of gold nanoparticles to efficiently convert near-infrared (NIR) light into heat makes them ideal candidates for photothermal applications, particularly in the treatment of deep-seated tumors. This research explores the design and synthesis of gold nanoparticles tailored for PTT, examining their physicochemical properties.
  • Methods: Gold nanoparticles (AuNPs) were synthesized by reducing HAuCl₄ (1 mM) with Sodium borohydride (NaBH₄, 0.1 M) in the presence of Cetyltrimethylammonium bromide (CTAB, 0.1 M) under vigorous stirring (12 h, 25 °C), followed by purification (10,000 rpm, 10 min). Then NPs were conjugated with carboxylated nanodiamonds via overnight stirring to yield ND-Au hybrids, which were isolated by centrifugation, washed, and lyophilized. Doxorubicin (DOX) was loaded onto ND-Au (1 mg/mL) by incubation (0.2 mg/mL DOX, 24 h, 25 °C), and the unbound drug was removed via centrifugation. Subsequently, hyaluronic acid coating was achieved by 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysulfosucnimide (EDC/NHS) activation (PBS buffer pH 7.4, 2 h), dialysis (MWCO=14 kDa, 48 h), and incubation with ND-Au-DOX (24 h, 25 °C). Photothermal properties were assessed under 450 nm laser irradiation (1 W/cm²), with temperature kinetics monitored using a high-precision laser thermometer. For pH-dependent release studies, samples in PBS (pH=5.4, 7.4) were dialyzed (MWCO=14 kDa) with NIR irradiation (450 nm, 1 W/cm², 5 min). At scheduled intervals, 1 mL aliquots were collected (replaced with fresh PBS) and analyzed to determine cumulative DOX release.
  • Results: Results indicated that NIR laser irradiation (450 nm) induced rapid and substantial heating of the nanocarriers, achieving localized temperatures up to 60 °C. This photothermal effect enabled precise spatiotemporal control of drug release kinetics. Quantitative analysis revealed pH-dependent release profiles, with approximately 50% DOX payload released at acidic pH (5.4), compared to <10% under physiological conditions (pH 7.4).
  • Conclusion: This study successfully developed an intelligent nanocarrier system responsive to both acidic pH and NIR laser irradiation. The results demonstrated a synergistic combination of pH-triggered bond cleavage and laser-induced thermal permeability enhancement (reaching 60 °C). By simultaneously leveraging intrinsic tumor markers (low pH) and external control (laser), this system shows remarkable potential for precision cancer targeting - maintaining excellent circulatory stability while enabling controlled drug activation. These findings represent a significant advancement toward personalized cancer therapy, with the nanocarrier demonstrating all key characteristics required for clinical translation: stability and controllable activation. Future work will focus on in vivo validation and optimization for specific cancer types.
  • Keywords: Photothermal therapy, Gold nanoparticles, Nanodiamond, Cancer