The literature data for this study was collected from the Scopus database [31]. An initial search was performed on 19 January 2024, using the query “TITLE-ABS-KEY (nanocellulose AND adhesives),” which yielded 237 documents. To refine the results, filters were applied to include only documents at the final publication stage (“Pubstage = Final”) and in English, resulting in a total of 225 documents. The search covered the period from January 2007 to January 2024. Documents meeting the inclusion criteria for analysis were exported in comma-separated value (*.csv) and research information system (.ris) formats. The metadata of each document was meticulously verified through manual inspection using Mendeley Reference Manager to ensure completeness, focusing specifically on titles, abstracts, and keywords.

Bibliometric analysis was conducted using VOSviewer version 1.6.18 for Windows, following established procedures as described in the literature [32]. The metadata utilized for the analysis included fields such as authors, co-authors, titles, abstracts, and keywords. A minimum threshold of five occurrences per term was applied, and duplicate or irrelevant keywords were removed to ensure the accuracy and relevance of the data. The refined data was then mapped using VOSviewer, which facilitated the visualization and assessment of emerging trends through bibliometric mapping. Three types of visualizations were generated: network visualization, density visualization, and overlay visualization, each illustrating co-citation networks and relationships among the items analyzed.

Bibliometric analysis using VOSviewer has been reported [33,34]. The progression of publications about nanocellulose and adhesives from 2007 to 2024 is shown in (Fig. 1).

A preliminary investigation was published on 22 November 2007 under the title “Modification of Nanocellulose With A Xyloglucan-RGD Conjugate Enhances Adhesion and Proliferation of Endothelial Cells: Implications for Tissue Engineering” [35]. As illustrated in Fig. 1, initial interest in nanocellulose-based adhesives was limited, with no research publications on the topic from 2008 to 2010. The field saw renewed activity in 2011 with just one publication. From 2019 to 2024, the number of related documents has fluctuated significantly. A noticeable increase in research interest began in 2017, marked by the publication of a book chapter titled “The Use of Wheat Straw as an Agricultural Waste in Composites for Semi-Structural Applications” [36], along with one article from the International Journal of Adhesion and Adhesives and a conference paper from the ICCM (International Conferences on Composite Materials) [37,38]. Interest in research on nanocellulose and adhesives is expected to continue growing throughout 2024, with further publications anticipated by the end of December 2024.

A VOSviewer can analyze author productivity and affiliation. Dubé, M.A., from the University of Ottawa in Ottawa, Canada, has the strongest bond strength with a total link strength of 43, 18 documents, and 149 citations. Dubé, M.A. collaborated with several authors, which are presented in (Fig. 2). Several countries that have published the most research on nanocellulose and adhesives can be seen in (Fig. 3). In terms of the number of publications, China holds the top position with 67 published documents, followed by the United States with 35 published documents.

After conducting a manual search in Mendeley Reference Manager and using the specified criteria, we obtained 207 papers. Fig. 4 displays the distribution of document types at the top and identifies the raw materials utilized in adhesive formulations at the bottom for the time spanning from 2007 to 2024. The data reveals that the predominant kind of publication consisted of articles, accounting for 87.4% of the total with 181 documents, closely followed by conference papers. A total of 10 papers, accounting for 4.8% of the total, consist of article reviews and book chapters. Each document includes up to 8 articles, representing 3.9% of the total. Multiple laboratory research endeavours focus on the development of diverse bio-based adhesives possessing superior quality, plentiful availability, sustainable characteristics, and renewable features. Researchers are explicitly exploring cellulose, nanocellulose, and modified nanocellulose as potential raw materials for wood binding purposes.

The results of a bibliometric analysis of keywords were used to generate the visual map, which is tabulated on the top 10 keywords with the highest links and total link strength. A link is a connection between two nodes that contain identical information about a paper, such as the names of two authors or keywords that describe the document’s contents [39]. The data in Table 1 shows that experiment journals almost always mention the terms “nanocellulose” and “adhesives”.

Keywords are nouns or phrases that can succinctly encapsulate the entirety of the significance or fundamental substance of a research study, hence facilitating the analysis of research patterns within a scientific field [39,40]. Co-occurrence keyword analysis is conducted to find terms that are often used together in one or more publications [41]. Fig. 5 shows three visualizations generated by VOSviewer using the terms [42]. Fig. 5a presents clusters representing each researched topic area in the form of network visualization. The terms “nanocellulose and adhesives” are included as keywords in this research. Fig. 5b illustrates an overlay visualization format that displays the year in which research on the most searched terms was conducted. Fig. 5c displays the density visualization of the frequency of phrase usage in research using density visualization. The hue of a phrase can be employed to evaluate its frequency of usage. The frequency of a word is directly proportional to the lightness of its color [43].

The analysis is conducted using Vosviewer, with a restriction of no more than five relationships between terms [42]. A comprehensive examination of 2770 frequently used terms in the field of nanocellulose-based adhesives revealed that only 105 keywords possess robust associations. These keywords are categorized into the subsequent 5 clusters. Table 2 shows the cluster details of the network visualization keywords.

The list of journals with the highest number of published documents can be seen in Table 3. Ten publishers were found to have released more than five documents during the period from 2007 to 2024. The journal with the most contributions was Carbohydrate Polymers, with 15 manuscripts and 308 citations, followed by Chemical Engineering Journal, with 10 manuscripts and 235 citations. The manuscripts listed in Table 3 generally have a rank in the first quartile (Q1) and third quartile (Q3), which shows that these journals have had a significant impact on the development of scientific disciplines, especially nanocellulose-based adhesives.

Highly cited manuscripts were subsequently subjected to an analysis. Evidently, the research influenced the respective authors, as the amount of citations is substantial. Based on citation results, the article with the title “Modification of nanocellulose with a xyloglucan-RGD conjugate enhances adhesion and proliferation of endothelial cells: Implications for tissue engineering,” published by Biomacromolecules in 2007, has the highest number of citations during the 2007–2024 period [35]. This suggests that the first study on cellulose-based adhesives inspired subsequent research and was built upon it.

Cellulose is the most abundant biopolymer in the world and is derived from renewable sources [85]. Cellulose production reaches 180 billion tons/year [86]. The widespread availability, low cost, and ease of processing cellulose have garnered the interest of researchers for their potential applications [87]. As adhesives, numerous modified cellulose derivatives have been developed and implemented, including ethyl cellulose [88], microcrystalline cellulose (MCC) [89], carboxymethyl cellulose (CMC) [62,90], dialdehyde cellulose (DAC) [91,92], and nanocellulose [76,93,94]. Nanocellulose, which is a cellulose derivative, exhibits extraordinary characteristics in comparison to other substances [95,96]. The increasing number of publications each year demonstrates the researchers’ deep interest in developing adhesives based on nanocellulose.

Nanocellulose, a cellulose-derived material at the nanoscale, primarily exists in two forms: cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC) [97]. CNF is widely used as a thickening agent in coatings and adhesives, as well as a reinforcing component in composite materials [98]. Conversely, CNC is employed in high-performance materials and composites, offering superior mechanical properties [99]. Future advancements in nanocellulose-based adhesives should align with the growing market trends towards a green economy, emphasizing sustainable and eco-friendly products. A key challenge in this area is the effective utilization of biomass as the primary resource for nanocellulose production, adhering to the biorefinery concept. This concept involves the comprehensive use of biomass to produce a diverse array of derivative products, including food, biomaterials, and bioenergy [100].

To increase cellulose’s physical characteristics and chemical resistance, cellulose modification is required [101,102]. The results of bibliometric analysis show numerous modification methods commonly used by researchers, such as cross-linking, oxidation, and hydrolysis. To develop nanocellulose-based adhesives, environmentally friendly cross-linkers and chemicals must be applied. GTA (glutaraldehyde) is an effective cross-linking agent for gluten, and the adhesive presents significant strength and water resistance [46]. In addition, in the research by Pang et al. [62], bio-based carboxymethylated wood fibers (CMWFs) were used to develop high-performance soybean meal-based adhesives. A carboxymethylation pretreatment was applied to wood fibre (WF) to provide a substantial number of carboxyl groups and facilitate its dispersion in the soy protein matrix. By forming a double “cross-linking core” with soy protein side chains, CMWF, composed of numerous carboxyl groups, enables a stable adhesive system. TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxyl)-catalyzed cellulose oxidation is a trending technique that facilitates the generation of CNF in quantity while maintaining energy efficiency and cost-effectiveness [103]. The acid hydrolysis technique was used to modify the nanocellulose because of its high mechanical strength and crystallinity [104].

CNF and CNC are potent bio-based compounds with great potential for reinforcing polymer matrices. To boost bonding performance, Kamboj et al. [105], a polyurethane adhesive (PUR) was created and reinforced with CNC and cellulose acetate nanofibers. Reinforced adhesive is used to prepare lap joints using spruce and beech wood. As a result, PUR combined with nanocellulose significantly increased elastic modulus by 33% in spruce wood but only by 12% in beech wood. Cyclic moisture exposure reduced the elasticity of both types of CNC-reinforced PUR. However, for the 0.5% CNF-reinforced PUR joint, the value increased by 5%. PUR reinforcement with nanocellulose significantly increased the shear strength of spruce wood by 45% more than that of beech wood by 35%. Meanwhile, CNF and CNC were strengthened on polyvinyl acetate (PVAc) adhesive. Adding nanocellulose to PVAc adhesive significantly increases the joint’s elastic stiffness and shear strength. Maximum elastic stiffness and shear strength values were achieved by adding 1% nanocellulose.

Researchers have become concerned about the future development of nanocellulose in biomedical applications. Nanocellulose has the potential to significantly advance biomedical materials of the next generation. It has been widely applied in medical implants, tissue engineering, drug delivery, wound healing, diagnostics, and other medical applications, with concrete examples in these fields. A study investigated the capability of CNC as drug delivery excipients to bind water-soluble antibiotics (tetracycline and doxorubicin) and the potential of cationic CNC to bind nonionizing hydrophobic anticancer agents (docetaxel, paclitaxel, and etoposide) [106]. An alternative method for spray-drying CNF tablets to produce tablets with a lower granular porosity than commercial MCC was demonstrated in another study examining the effects of spray-drying treatment on CNF tablets [107]. Implementing nanocellulose-based adhesives offers cost-effectiveness and scalability benefits, thereby facilitating their extensive application in the medical field.

To enhance industrial application, the development of nanocellulose in polymer composites faces several challenges. The most significant barrier is the high production cost. According to Kaur et al. (2021), factors such as the cost of raw materials, pre-treatment methods, and acids used for hydrolysis influence overall production expenses [108]. For instance, using organic acids like citric acid for cellulose nanocrystal (CNC) production reduces capital costs by approximately 40% compared to strong acids like sulfuric acid, offering a more economically and environmentally friendly alternative. Researchers are also exploring enzymatic nanocellulose synthesis as a cost-effective substitute for expensive chemicals.

Squinca et al. highlight that the cost of producing nanocellulose depends on product type, production scale, raw material source, and the technology employed [109]. Specialized equipment, such as high-pressure homogenizers, can increase production expenses, while the costs of chemicals like hydrogen peroxide and sulfuric acid also contribute. Additionally, drying, storage, and transportation processes further influence production costs. As the demand for nanocellulose continues to grow, there is a push to develop more efficient and sustainable production methods. Nevertheless, economic challenges persist, including the limited commercial availability of nanocellulose and the absence of standardized production methods and regulations. Costs are anticipated to decline as new, sustainable production technologies are developed.

Furthermore, Shen et al. investigated the barriers to commercializing polymer composites enhanced with nanocellulose, identifying issues related to functionalization and large-scale production [110]. One key challenge is ensuring compatibility between nanocellulose and polymer matrices. Functionalizing nanocellulose to improve interfacial bonding and overall composite performance is essential, yet diverse techniques are required to achieve the complex synergistic effects needed when combining nanocellulose with other nanofillers. These challenges underscore the need for further research to increase production capacity and optimise costs. The commercialization of nanocellulose-reinforced composites hinges on reducing their high costs and addressing the need for pre-treatment before integration into polymer matrices.