Carrier-free drugs as smart nanomaterials for cancer theranostics

Abstract

Nanocarriers have gained widespread applications in cancer theranostics by incorporating the fundamental concepts of nanotechnology. Drug delivery systems (DDS) based out of nanocarriers have outstanding prospects for biomedical applications due to their remarkable blood distribution, superior retention of drugs in tumors, and enhanced potential for combination therapy. However, two significant barriers have impeded the advancement of nanocarriers: the possibility of nanocarrier toxicity and poor loading of drugs into the nano DDS. Carrier-free drugs (CFDs) delivery nanosystems are an inventive alternative to these challenges and have drawn much interest in cancer therapy and stand out as an achievable solution to these obstacles. CFDs are developed on a nanoscale, without any requirement of additional excipients, and consequently have excellent pharmacokinetics and intracellular delivery. The key highlights of this review include preparation techniques, pharmacokinetics, covalent, non-covalent interactions and optimization of CFDs. The potential of CFDs in cancer theranostics is explored under specific interactions based on drugs, such as drug-drug, drug-photosensitizer, drug-metal, drug-antibody, and drug-peptide interactions. To the best of our knowledge, this review is the first to discuss the design of carrier-free drugs for cancer theranostics, with a prime focus on drug-based interactions that serve as the major basis for their self-assembly. Thus, by addressing the multifaceted aspects of CFDs, the review attempts to present a comprehensive perspective of CFDs and provide novel insights for more effective cancer therapeutics.