Preface

Chapter 8 **Nuclear Medicine and Drug Delivery 159**

Coelho

**VI** Contents

Ana Rita Fernandes, Ana Oliveira, Jorge Pereira and Pedro Silva

The drug delivery system (DDS) translates drug discovery and pharmacological research in‐ to clinical practice. The treatment of acute diseases or chronic illness is accomplished by de‐ livery of drugs to patients using various pharmaceutical dosage forms. The conventional dosage forms, which provide a prompt release of a drug, are the major pharmaceutical products in the markets. The use of conventional dosage forms results in significant fluctua‐ tions in plasma drug levels and therefore, multiple dosing has been suggested to maintain plasma drug concentration for effective treatment.

To achieve as well as to maintain the drug concentration within the therapeutically effective range and prevent fluctuations in plasma drug levels, new DDS has emerged. The science and technology responsible for the development of new DDS have been the focus of a great deal of attention in both industrial and academic laboratories. Because novel DDS can con‐ trol the rate of drug release, sustain the duration of therapeutic activity, and/or target the drug to a tissue, they are expected to revolutionize the method of medication with a number of potential therapeutic benefits including patient compliance and reduced side effects.

The current focus in delivery system design is shifting to a 'smart drug' paradigm, in which increased efficacy, stability against biochemical degradation and decreased toxicity are the motivating factors. This could be achieved with targeted nanoparticles, where repertoires of targets and a series of drugs could yield new generations of highly specific therapeutic agents. The ultimate goal of nanodrug delivery systems is to develop clinically useful for‐ mulations for treating diseases. In cases where remote organs or cells (such as cells within solid tumors) are the targets, there is still a need to find ways to navigate nanoparticles through the labyrinth to the target site while avoiding clearance. Toward that goal, there have been reports of using hydrophilic coatings to achieve enhanced circulation time. Even with breakthroughs in the engineering of long-circulating nanoparticles, there is still the ad‐ ditional challenge of understanding and achieving the dosing that delivers consistent phar‐ macokinetics. In order to transform nanotechnologies from basic research into clinical products, it is important to understand how the biodistribution of NPs, which is primarily governed by their ability to negotiate biological barriers, affects the body's complex biologi‐ cal network, as well as mass transport across compartmental boundaries in the body. Ex‐ perts from different disciplines are putting their efforts together to translate novel laboratory innovation into commercially viable medical products. Optimizing the integra‐ tion of nanomaterials into drug delivery systems may result in a better understanding of the interactions of nanomaterials with biological systems, which will facilitate better engineer‐ ing of their properties specific to biomedical applications. The development of such drug carriers will require a greater understanding of both the surface chemistry of nanomaterials and the interaction chemistry of these nanomaterials with biological systems. Understand‐

ing both the benefits and the risks of these new nanotechnology applications will be essen‐ tial to good decision-making for drug developers, regulators and ultimately the consumers and patients who will be the beneficiaries of new drug delivery technologies. Advances in this area have allowed some nanomedicines in the market to achieve desirable pharmacoki‐ netic properties, reduce toxicity and improve patient compliance, as well as clinical out‐ comes. In addition, several other experimental drug delivery systems have shown exciting signs of promise, including those composed of biodegradable polymers. It is not possible to cover all the innovative ideas in this book. This book is designed to fulfill a perceived need to provide a comprehensive picture of some novel drug delivery systems. To accomplish this task, we have organized the book in the following manner. The book starts with an in‐ troductory chapter to gain preliminary understanding on the topics and explain significance of the content covered in this book. In recent days, nanotechnology represents a powerful tool in the field of medicine to combat a plethora of diseases. Thus, the nanoscale structures (< 1000 nm) enable targeted delivery to the site of action resulting in higher therapeutic effi‐ cacy and are therefore extensively used as therapeutic carriers. Gene therapy is a medical intervention that uses genes for the treatment or prevention of disease. The biocompatible nanoparticles have been investigated for gene therapy to overcome the disadvantages en‐ countered with the traditional methods used for genetic material delivery. The application of nanoparticles in gene delivery is illustrated in Chapter 2. Compared to polymeric nano‐ particles, lipid-based nanoparticles have long been perceived as the more ideal drug deliv‐ ery vehicles because of their superior biocompatibility. In Chapter 3, lipid-based nano drug delivery systems that are currently being investigated are discussed along with optimization and in vitro characterization procedures. To address the limitations of polymeric nanoparti‐ cles and lipid nanocarriers, a new generation delivery vehicle of therapeutics, termed hybrid nanoparticles, has drawn the attention of researchers. Therefore, the drug delivery applica‐ tions of hybrid nanocarriers have been included in Chapter 4. This is followed by Chapter 5 that discloses the potential of mucosal route for improving olfactory drug delivery. Chapter 6 illustrates plasma drug delivery in order to enhance percutaneous absorption of drugs, an approach different from the use of conventional skin permeation enhancers. Till now, the safe and efficient delivery of therapeutic genes to the diseased cells has been a major chal‐ lenge. Although viral vectors display good transduction properties, the safety issues are still to be solved. Meanwhile, considerable progress has been noticed in developing biopolymerbased non-viral expression vectors. Hence, Chapter 7 has been devoted to a discussion on potential application of biomaterial as non-viral vectors for gene delivery. The assistance of nuclear medicine in identifying drug delivery system in the body and its biodistribution characteristics is deeply appreciated in Chapter 8.

Hopefully, these topics will enrich readers with better understanding, broad perspectives, and an insight into the current state and future promises. This book would serve as a useful resource for pharmacy students, teaching professionals, medical and biomedical research‐ ers, and those working in the field of polymer and biological sciences.

The book is aimed at those who are interested in understanding the fundamentals and prog‐ ress of drug delivery technology. We would be happy if the content of this book creates in‐ terest among pharmaceutical scientists and augment the drug delivery research in bringing novel formulations for the benefit of humanity.

We would like to express our sincere gratitude to all the authors for their contribution to accomplish this book project. The various sources of information related to the content of

our book are cited in each chapter and are gratefully acknowledged. We are also thankful to our family members who motivated us for the successful completion of this book project. We are thankful to InTech publisher for their keen interest and expert assistance in the pub‐ lication of the book.

ing both the benefits and the risks of these new nanotechnology applications will be essen‐ tial to good decision-making for drug developers, regulators and ultimately the consumers and patients who will be the beneficiaries of new drug delivery technologies. Advances in this area have allowed some nanomedicines in the market to achieve desirable pharmacoki‐ netic properties, reduce toxicity and improve patient compliance, as well as clinical out‐ comes. In addition, several other experimental drug delivery systems have shown exciting signs of promise, including those composed of biodegradable polymers. It is not possible to cover all the innovative ideas in this book. This book is designed to fulfill a perceived need to provide a comprehensive picture of some novel drug delivery systems. To accomplish this task, we have organized the book in the following manner. The book starts with an in‐ troductory chapter to gain preliminary understanding on the topics and explain significance of the content covered in this book. In recent days, nanotechnology represents a powerful tool in the field of medicine to combat a plethora of diseases. Thus, the nanoscale structures (< 1000 nm) enable targeted delivery to the site of action resulting in higher therapeutic effi‐ cacy and are therefore extensively used as therapeutic carriers. Gene therapy is a medical intervention that uses genes for the treatment or prevention of disease. The biocompatible nanoparticles have been investigated for gene therapy to overcome the disadvantages en‐ countered with the traditional methods used for genetic material delivery. The application of nanoparticles in gene delivery is illustrated in Chapter 2. Compared to polymeric nano‐ particles, lipid-based nanoparticles have long been perceived as the more ideal drug deliv‐ ery vehicles because of their superior biocompatibility. In Chapter 3, lipid-based nano drug delivery systems that are currently being investigated are discussed along with optimization and in vitro characterization procedures. To address the limitations of polymeric nanoparti‐ cles and lipid nanocarriers, a new generation delivery vehicle of therapeutics, termed hybrid nanoparticles, has drawn the attention of researchers. Therefore, the drug delivery applica‐ tions of hybrid nanocarriers have been included in Chapter 4. This is followed by Chapter 5 that discloses the potential of mucosal route for improving olfactory drug delivery. Chapter 6 illustrates plasma drug delivery in order to enhance percutaneous absorption of drugs, an approach different from the use of conventional skin permeation enhancers. Till now, the safe and efficient delivery of therapeutic genes to the diseased cells has been a major chal‐ lenge. Although viral vectors display good transduction properties, the safety issues are still to be solved. Meanwhile, considerable progress has been noticed in developing biopolymerbased non-viral expression vectors. Hence, Chapter 7 has been devoted to a discussion on potential application of biomaterial as non-viral vectors for gene delivery. The assistance of nuclear medicine in identifying drug delivery system in the body and its biodistribution

Hopefully, these topics will enrich readers with better understanding, broad perspectives, and an insight into the current state and future promises. This book would serve as a useful resource for pharmacy students, teaching professionals, medical and biomedical research‐

The book is aimed at those who are interested in understanding the fundamentals and prog‐ ress of drug delivery technology. We would be happy if the content of this book creates in‐ terest among pharmaceutical scientists and augment the drug delivery research in bringing

We would like to express our sincere gratitude to all the authors for their contribution to accomplish this book project. The various sources of information related to the content of

characteristics is deeply appreciated in Chapter 8.

VIII Preface

novel formulations for the benefit of humanity.

ers, and those working in the field of polymer and biological sciences.
